RESUMEN

BACKGROUND: To determine whether alternating bouts of sitting and standing at work influences daily workplace energy expenditure (EE). METHODS: Twenty-three overweight/obese office workers (mean ± SD; age: 48.2 ± 7.9 y, body mass index: 29.6 ± 4.0 kg/m2) undertook two 5-day experimental conditions in an equal, randomized order. Participants wore a "metabolic armband" (SenseWear Armband Mini) to estimate daily workplace EE (KJ/8 h) while working (1) in a seated work posture (SIT condition) or (2) alternating between a standing and seated work posture every 30 minutes using a sit-stand workstation (STAND-SIT condition). To assess the validity of the metabolic armband, a criterion measure of acute EE (KJ/min; indirect calorimetry) was performed on day 4 of each condition. RESULTS: Standing to work acutely increased EE by 0.7 [95% CI 0.3-1.0] KJ/min (13%), relative to sitting (P = .002). Compared with indirect calorimetry, the metabolic armband provided a valid estimate of EE while standing to work (mean bias: 0.1 [-0.3 to 0.4] KJ/min) but modestly overestimated EE while sitting (P = .005). Daily workplace EE was greatest during the STAND-SIT condition (mean condition difference [95% CI]: 76 [8-144] KJ/8-h workday, P = .03). CONCLUSIONS: Intermittent standing at work can modestly increase daily workplace EE compared with seated work in overweight/obese office workers.

Asunto(s)

Metabolismo Energético/fisiología , Sobrepeso/terapia , Lugar de Trabajo/psicología , Estudios de Casos y Controles , Femenino , Humanos , Masculino , Persona de Mediana Edad , Conducta Sedentaria

RESUMEN

AIM: To examine the effect of renal denervation (RDN) on blood pressure (BP) and health-related quality of life (QoL) in patients with resistant hypertension, pseudoresistant hypertension due to a white-coat effect and in patients with uncontrolled masked hypertension. METHODS: Using the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), Beck Depression Inventory (BDI) and Spielberger's state and trait anxiety questionnaires, we examined QoL, symptoms of depression and anxiety prior to and 12 months following RDN. BP was assessed from clinic and ambulatory blood pressure monitoring (ABPM) recordings. RESULTS: Patients with uncontrolled masked hypertension had the highest BDI and anxiety scores among all groups at baseline. Twelve months following RDN clinic and ambulatory BP were reduced only in those patients with resistant hypertension (delta SBP: clinic -16 ±â€Š3 mmHg, ABPMday -8 ±â€Š2 mmHg, ABPMnight -8 ±â€Š2 mmHg, all P < 0.01). Clinic BP was reduced in the pseudoresistant group (-17 ±â€Š6 mmHg, P < 0.01) but was elevated in the uncontrolled masked group (+13 ±â€Š6 mmHg, P = 0.02). In all patients, trait anxiety (P < 0.05), BDI scores (P < 0.05) and the SF-36 mental component summary (MCS) score (P < 0.001) were improved. The improvement in the SF-36 MCS was confined to those patients with resistant hypertension (+4.0 ±â€Š1.1, P < 0.01). The change in clinic BP after RDN was related to the baseline clinic BP (systolic: r = 0.54, P < 0.001; diastolic r = 0.43, P < 0.001), the number of ablations delivered (both clinic and mean day ABPM systolic r = 0.24, P < 0.05) and to the change in SF-36 MCS score (systolic: r = 0.25, P = 0.01; diastolic r = 0.24, P = 0.02). CONCLUSION: These results indicate that in patients with confirmed resistant hypertension, RDN is associated with a reduction in BP and a sustained improvement in mental health-related aspects of QoL.

Asunto(s)

Presión Sanguínea/fisiología , Desnervación/métodos , Hipertensión/cirugía , Riñón/inervación , Calidad de Vida , Anciano , Determinación de la Presión Sanguínea , Monitoreo Ambulatorio de la Presión Arterial/métodos , Femenino , Estudios de Seguimiento , Estado de Salud , Humanos , Hipertensión/fisiopatología , Hipertensión/psicología , Riñón/fisiopatología , Masculino , Persona de Mediana Edad

RESUMEN

Animal and human studies have demonstrated that chronic activation of renal sympathetic nerves is critical in the pathogenesis and perpetuation of treatment-resistant hypertension. Bilateral renal denervation has emerged as a safe and effective, non-pharmacological treatment for resistant hypertension that involves the selective ablation of efferent and afferent renal nerves to lower blood pressure. However, the most recent and largest randomized controlled trial failed to confirm the primacy of renal denervation over a sham procedure, prompting widespread re-evaluation of the therapy's efficacy. Disrupting renal afferent sympathetic signaling to the hypothalamus with renal denervation lowers central sympathetic tone, which has the potential to confer additional clinical benefits beyond blood pressure control. Specifically, there has been substantial interest in the use of renal denervation as either a primary or adjunct therapy in pathological conditions characterized by central sympathetic overactivity such as renal disease, heart failure and metabolic-associated disorders. Recent findings from pre-clinical and proof-of-concept studies appear promising with renal denervation shown to confer cardiovascular and metabolic benefits, largely independent of changes in blood pressure. This review explores the pathological rationale for targeting sympathetic renal nerves for blood pressure control. Latest developments in renal nerve ablation modalities designed to improve procedural success are discussed along with prospective findings on the efficacy of renal denervation to lower blood pressure in treatment-resistant hypertensive patients. Preliminary evidence in support of renal denervation as a possible therapeutic option in disease states characterized by central sympathetic overactivity is also presented.

RESUMEN

Sympathetic tone is well recognised as being implicit in cardiovascular control. It is less readily acknowledged that activation of the sympathetic nervous system is integral in energy homeostasis and can exert profound metabolic effects. Accumulating data from animal and human studies suggest that central sympathetic overactivity plays a pivotal role in the aetiology and complications of several metabolic conditions that can cluster to form the Metabolic Syndrome (MetS). Given the known augmented risk for type 2 diabetes, cardiovascular disease, and premature mortality associated with the MetS understanding the complex pathways underlying the metabolic derangements involved has become a priority. Many factors have been proposed to contribute to increased sympathetic nerve activity in metabolic abnormalities including obesity, impaired baroreflex sensitivity, hyperinsulinemia, and elevated adipokine levels. Furthermore there is mounting evidence to suggest that chronic sympathetic overactivity can potentiate two of the key metabolic alterations of the MetS, central obesity and insulin resistance. This review will discuss the regulatory role of the sympathetic nervous system in metabolic control and the proposed pathophysiology linking sympathetic overactivity to metabolic abnormalities. Pharmacological and device-based approaches that target central sympathetic drive will also be discussed as possible therapeutic options to improve metabolic control in at-risk patient cohorts.

Asunto(s)

Síndrome Metabólico/fisiopatología , Obesidad/fisiopatología , Sistema Nervioso Simpático/fisiopatología , Animales , Humanos

RESUMEN

BACKGROUND/AIM: Sedentary behaviour is associated with increased risk for all-cause and cardiovascular mortality. Plasma fibrinogen and C reactive protein (CRP)-key inflammatory and/or haemostatic markers-may contribute to this association; however, few studies have examined their relationships with sedentary behaviours. We examined associations of overall sitting and TV viewing time with fibrinogen and high-sensitivity CRP (hsCRP). METHODS: Plasma fibrinogen and hsCRP were measured in 3086 Australian adults (mean age: 55±12 years) who participated in the 2004-2005 AusDiab (Australian Diabetes, Obesity and Lifestyle) study. Multiple linear regression analyses examined cross-sectional associations of self-reported overall sitting and TV viewing time (h/day) with plasma fibrinogen and hsCRP, adjusting for sociodemographic, behavioural and medical treatments and conditions as potential covariates. RESULTS: Overall sitting time and TV viewing time were positively associated with plasma fibrinogen (sitting: ß: 0.02 g/L, 95% CI (0.01 to 0.02); TV time: 0.03 g/L (0.02 to 0.05)) and hsCRP (sitting: 2.4% (1.2% to 3.6%); TV time: 4.5% (1.7% to 7.4%)). Associations were independent of leisure-time physical activity, but after adjusting for waist circumference, they remained for fibrinogen, but for hsCRP were attenuated to the null. Interactions were observed for gender×TV (p=0.011) with fibrinogen (associations in women only) and for waist circumference×TV (p=0.084) with hsCRP (associations in low-risk only). CONCLUSIONS: Overall sitting time was positively associated with plasma fibrinogen and hsCRP in men and women; associations of TV viewing time with fibrinogen were observed in women only. Abdominal adiposity-mediated associations for hsCRP but not for fibrinogen. Prospective and intervention studies are needed to establish likely causality and elucidate potential mechanisms.

Asunto(s)

Proteína C-Reactiva/metabolismo , Fibrinógeno/metabolismo , Conducta Sedentaria , Televisión , Biomarcadores/metabolismo , Estudios Transversales , Femenino , Humanos , Actividades Recreativas , Masculino , Persona de Mediana Edad , Factores de Tiempo , Circunferencia de la Cintura

RESUMEN

OBJECTIVES: To examine whether the introduction of intermittent standing bouts during the workday using a height-adjustable workstation can improve subjective levels of fatigue, musculoskeletal discomfort and work productivity relative to seated work. METHODS: Overweight/obese office workers (n=23; age 48.2±7.9 years, body mass index 29.6±4 kg/m(2)) undertook two, 5-day experimental conditions in an equal, randomised (1:1) order. In a simulated office environment, participants performed their usual occupational tasks for 8 h/day in a: seated work posture (SIT condition); or interchanging between a standing and seated work posture every 30 min using an electric, height-adjustable workstation (STAND-SIT condition). Self-administered questionnaires measuring fatigue, musculoskeletal discomfort and work productivity were performed on day 5 of each experimental condition. RESULTS: Participants' total fatigue score was significantly higher during the SIT condition (mean 67.8 (95% CI 58.8 to 76.7)) compared with the STAND-SIT condition (52.7 (43.8 to 61.5); p<0.001). Lower back musculoskeletal discomfort was significantly reduced during the STAND-SIT condition compared with the SIT condition (31.8% reduction; p=0.03). Despite concentration/focus being significantly higher during the SIT condition (p=0.006), there was a trend towards improved overall work productivity in favour of the STAND-SIT condition (p=0.053). CONCLUSIONS: Transitioning from a seated to a standing work posture every 30 min across the workday, relative to seated work, led to a significant reduction in fatigue levels and lower back discomfort in overweight/obese office workers, while maintaining work productivity. Future investigations should be directed at understanding whether sustained use of height-adjustable workstations promote concentration and productivity at work. TRIAL REGISTRATION NUMBER: ACTRN12611000632998.

Asunto(s)

Fatiga/prevención & control , Dolor Musculoesquelético/prevención & control , Obesidad/complicaciones , Enfermedades Profesionales/prevención & control , Exposición Profesional/efectos adversos , Postura , Conducta Sedentaria , Adulto , Ergonomía , Fatiga/etiología , Femenino , Humanos , Masculino , Dolor Musculoesquelético/etiología , Enfermedades Profesionales/etiología , Sobrepeso/complicaciones , Encuestas y Cuestionarios , Trabajo , Lugar de Trabajo

RESUMEN

PURPOSE: This study aimed to examine whether reductions in sitting time through alternating 30-min bouts of sitting and standing can reduce postprandial glucose, insulin, and triglyceride responses. METHODS: Twenty-three overweight/obese sedentary office workers (17 males and six females; mean ± SD: age, 48.2 ± 7.9 yr; body mass index, 29.6 ± 4.0 kg · m(-2)) undertook two short-term (5 d) experimental conditions in an equal, randomized (1:1) order. In a simulated office environment, participants performed typical occupational tasks for 8 h · d(-1) while in a 1) seated work posture (control condition) or 2) interchanging between a seated and standing work posture every 30 min using an electric, height-adjustable workstation (intervention condition). Fasting and postprandial blood samples after a mixed test drink were collected hourly for 4 h on days 1 and 5 of each condition to assess serum insulin, plasma glucose, and triglycerides. Dietary intake (kJ · d(-1)) and physical activity were standardized during each condition. The trial was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12611000632998). RESULTS: After adjustment for time (days 1 and 5), incremental area under the analyte time curve differed significantly between conditions for plasma glucose (P = 0.007) but not for serum insulin or plasma triglycerides. Adjusted mean glucose incremental area under the analyte time curve was lowered by 11.1% after the intervention condition (6.38 mM · h(-1) (confidence interval, 5.04-7.71)) relative to the control condition (7.18 mM · h(-1) (confidence interval, 5.85-8.52)). No temporal changes (days 1 vs 5) between conditions were observed. CONCLUSIONS: Alternating standing and sitting in 30-min bouts results in modest beneficial effects on postprandial glucose responses in overweight/obese office workers.

Asunto(s)

Glucemia/metabolismo , Obesidad/sangre , Sobrepeso/sangre , Periodo Posprandial , Postura/fisiología , Conducta Sedentaria , Adulto , Anciano , Femenino , Humanos , Insulina/sangre , Masculino , Persona de Mediana Edad , Triglicéridos/sangre , Lugar de Trabajo

RESUMEN

PURPOSE OF REVIEW: The relationship between excessive sympathetic drive to the kidneys and hypertension is now well established. This has led to the development of therapeutic approaches, such as catheter-based bilateral renal denervation, for the treatment of resistant hypertension. The purpose of this article is to review the sympathetic regulation of kidney function, with specific focus given to clinical insights gained from human studies involving renal denervation and animal studies that have identified possible causal factors associated with disease. RECENT FINDINGS: Continuous chronic determinations of renal sympathetic nerve activity (RSNA) in animal models have recently identified a role of angiotensin II and obesity in the initiation of neurally related hypertension. Other potential mediating factors influencing RSNA include adipose tissue derived factors, neurohumoral pathways and baroreceptor-mediated mechanisms. Hypertension development is likely to reflect a combination of these factors. Interventions that directly interrupt renal sympathetic signaling show promising results in the treatment of resistant hypertension. SUMMARY: The mechanisms underlying the development of neurogenic hypertension are beginning to be elucidated, thanks to technological advancements that enable the direct measurement of RSNA. Determining factors associated with hypertension development will help to identify strategies to mitigate disease as well as provide scientific support for novel nonpharmacologic therapies.

Asunto(s)

Presión Sanguínea , Hipertensión/fisiopatología , Riñón/inervación , Sistema Nervioso Simpático/fisiopatología , Animales , Modelos Animales de Enfermedad , Humanos , Hipertensión/cirugía , Simpatectomía , Sistema Nervioso Simpático/cirugía , Resultado del Tratamiento

RESUMEN

A number of intervention studies have reported that the prevalence of obesity may be in part inversely related to dairy food consumption while others report no association. We sought to examine relationships between energy, protein and calcium consumption from dairy foods (milk, yoghurt, cheese, dairy spreads, ice-cream) and adiposity including body mass index (BMI), waist (WC) and hip circumference (HC), and direct measures of body composition using dual energy X-ray absorptiometry (% body fat and abdominal fat) in an opportunistic sample of 720 overweight/obese Australian men and women. Mean (SD) age, weight and BMI of the population were 51 ± 10 year, 94 ± 18 kg and 32.4 ± 5.7 kg/m2, respectively. Reduced fat milk was the most commonly consumed dairy product (235 ± 200 g/day), followed by whole milk (63 ± 128 g/day) and yoghurt (53 ± 66 g/day). Overall dairy food consumption (g/day) was inversely associated with BMI, % body fat and WC (all p < 0.05). Dairy protein and dairy calcium (g/day) were both inversely associated with all adiposity measures (all p < 0.05). Yoghurt consumption (g/day) was inversely associated with % body fat, abdominal fat, WC and HC (all p < 0.05), while reduced fat milk consumption was inversely associated with BMI, WC, HC and % body fat (all p < 0.05). Within a sample of obese adults, consumption of dairy products, dairy protein, and calcium was associated with more favourable body composition.

Asunto(s)

Composición Corporal , Calcio de la Dieta/uso terapéutico , Productos Lácteos , Dieta , Conducta Alimentaria , Proteínas de la Leche/uso terapéutico , Obesidad/prevención & control , Tejido Adiposo/metabolismo , Adiposidad/efectos de los fármacos , Adulto , Animales , Composición Corporal/efectos de los fármacos , Calcio de la Dieta/farmacología , Proteínas en la Dieta/farmacología , Proteínas en la Dieta/uso terapéutico , Ingestión de Energía , Femenino , Cadera , Humanos , Masculino , Persona de Mediana Edad , Leche , Proteínas de la Leche/farmacología , Circunferencia de la Cintura , Yogur

RESUMEN

PURPOSE OF REVIEW: The aim is to provide clinicians with a concise update on renal sympathetic nerve ablation in the management of resistant hypertension. The review will specifically discuss the latest clinical trial findings, technological advancements in ablation modalities and expert guidelines for patient eligibility. Novel therapeutic applications beyond blood pressure (BP) control will also be discussed. RECENT FINDINGS: Follow-up data from the Symplicity Clinical Trials Program provides further evidence for the safety of the procedure and substantiates a sustained reduction in BP in most patients with resistant hypertension. Recently published expert consensus statements recommend that only patients with resistant hypertension should undergo the procedure at this stage. Several alternative treatment modalities for renal denervation have been developed to improve efficacy, procedure time and safety. Initial findings suggest comparable BP reductions amongst technical approaches. Several pilot studies, although predominantly uncontrolled, indicate additional benefits of renal sympathetic nerve ablation on regression of hypertensive end-organ damage, heart failure, cardiac arrhythmias and other disturbances commonly associated with resistant hypertension. SUMMARY: Catheter-based renal nerve ablation is emerging as a well tolerated, effective and cost-effective treatment to control BP in patients with resistant hypertension. Further studies are required to determine the long-term impact of this novel therapeutic option.

Asunto(s)

Hipertensión/cirugía , Riñón/inervación , Riñón/cirugía , Simpatectomía/métodos , Presión Sanguínea , Ablación por Catéter/métodos , Ablación por Catéter/tendencias , Ensayos Clínicos como Asunto , Humanos , Hipertensión/fisiopatología , Selección de Paciente , Guías de Práctica Clínica como Asunto , Simpatectomía/tendencias

RESUMEN

BACKGROUND: Television (TV) viewing time is positively associated with the metabolic syndrome (MetS) in adults. However, the mechanisms through which TV viewing time is associated with MetS risk remain unclear. There is evidence that the consumption of energy-dense, nutrient poor snack foods increases during TV viewing time among adults, suggesting that these behaviors may jointly contribute towards MetS risk. While the association between TV viewing time and the MetS has previously been shown to be independent of adult's overall dietary intake, the specific influence of snack food consumption on the relationship is yet to be investigated. The purpose of this study was to examine the independent and joint associations of daily TV viewing time and snack food consumption with the MetS and its components in a sample of Australian adults. METHODS: Population-based, cross-sectional study of 3,110 women and 2,572 men (>35 years) without diabetes or cardiovascular disease. Participants were recruited between May 1999 and Dec 2000 in the six states and the Northern Territory of Australia. Participants were categorised according to self-reported TV viewing time (low: 0-2 hr/d; high: >2 hr/d) and/or consumption of snack foods (low: 0-3 serves/d; high: >3 serves/d). Multivariate odds ratios [95% CI] for the MetS and its components were estimated using gender-specific, forced entry logistic regression. RESULTS: OR [95% CI] for the MetS was 3.59 [2.25, 5.74] (p≤0.001) in women and 1.45 [1.02, 3.45] (p = 0.04) in men who jointly reported high TV viewing time and high snack food consumption. Obesity, insulin resistance and hypertension (women only) were also jointly associated with high TV viewing time and high snack food consumption. Further adjustment for diet quality and central adiposity maintained the associations in women. High snack food consumption was also shown to be independently associated with MetS risk [OR: 1.94 (95% CI: 1.45, 2.60), p < 0.001] and hypertension [OR: 1.43 (95% CI: 1.01, 2.02), p = 0.05] in women only. For both men and women, high TV viewing time was independently associated with the MetS and its individual components (except hypertension). CONCLUSION: TV viewing time and snack food consumption are independently and jointly associated with the MetS and its components, particularly in women. In addition to physical activity, population strategies targeting MetS prevention should address high TV time and excessive snack food intake.

Asunto(s)

Síndrome Metabólico/epidemiología , Obesidad/epidemiología , Conducta Sedentaria , Bocadillos , Televisión , Australia/epidemiología , Índice de Masa Corporal , Estudios Transversales , Dieta , Ingestión de Energía , Conducta Alimentaria , Femenino , Estudios de Seguimiento , Calidad de los Alimentos , Conductas Relacionadas con la Salud , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , Análisis Multivariante , Prevalencia , Autoinforme

RESUMEN

BACKGROUND: To examine sedentary time, prolonged sedentary bouts and physical activity in Australian employees from different workplace settings, within work and non-work contexts. METHODS: A convenience sample of 193 employees working in offices (131), call centres (36) and customer service (26) was recruited. Actigraph GT1M accelerometers were used to derive percentages of time spent sedentary (<100 counts per minute; cpm), in prolonged sedentary bouts (≥20 minutes or ≥30 minutes), light-intensity activity (100-1951 cpm) and moderate-to-vigorous physical activity (MVPA; ≥1952 cpm). Using mixed models adjusted for confounders, these were compared for: work days versus non-work days; work hours versus non-work hours (work days only); and, across workplace settings. RESULTS: Working hours were mostly spent sedentary (77.0%, 95%CI: 76.3, 77.6), with approximately half of this time accumulated in prolonged bouts of 20 minutes or more. There were significant (p<0.05) differences in all outcomes between workdays and non-work days, and, on workdays, between work- versus non-work hours. Results consistently showed "work" was more sedentary and had less light-intensity activity, than "non-work". The period immediately after work appeared important for MVPA. There were significant (p<0.05) differences in all sedentary and activity outcomes occurring during work hours across the workplace settings. Call-centre workers were generally the most sedentary and least physically active at work; customer service workers were typically the least sedentary and the most active at work. CONCLUSION: The workplace is a key setting for prolonged sedentary time, especially for some occupational groups, and the potential health risk burden attached requires investigation. Future workplace regulations and health promotion initiatives for sedentary occupations to reduce prolonged sitting time should be considered.

Asunto(s)

Ejercicio Físico , Conductas Relacionadas con la Salud , Actividad Motora , Ocupaciones , Conducta Sedentaria , Trabajo , Lugar de Trabajo , Actigrafía , Adulto , Estudios Transversales , Femenino , Humanos , Masculino , Persona de Mediana Edad , Adulto Joven

RESUMEN

PURPOSE: To understand the prevalence and potential health effect of prolonged workplace sedentary (sitting) time, valid measures are required. Here, we examined the criterion validity of a brief self-reported measure of workplace sitting time and breaks in sitting time. METHODS: An interviewer-administered questionnaire was used to assess workplace sitting time (h·d(-1)) and breaks from sitting per hour at work in a convenience sample of 121 full-time workers (36% men, mean age = 37 yr, 53% office based). These self-reported measures were compared with accelerometer-derived sedentary time (hours per day, <100 counts per minute) and breaks per sedentary hour (number of times, ≥100 counts per minute) during work hours. RESULTS: Self-reported sitting time was significantly correlated with accelerometer-derived sedentary time (Pearson r = 0.39, 95% confidence interval = 0.22-0.53), with an average sitting time 0.45 h·d(-1) higher than average sedentary time. Bland-Altman plots and regression analysis showed positive associations between the difference in sitting and sedentary time and the average of sitting and sedentary time (mean difference = -2.75 h + 0.47 × average sitting and sedentary time; limits of agreement = ±2.25 h·d(-1)). The correlation of self-reported breaks per sitting hour with accelerometer-derived breaks per sedentary hour was also statistically significant (Spearman rs = 0.26, 95% confidence interval = 0.11-0.44). CONCLUSIONS: This study is the first to examine the criterion validity of an interviewer-administered questionnaire measure of workplace sitting time and breaks in sitting time using objective criterion measures. The workplace sitting measure has acceptable properties for use in observational studies concerned with sedentary behavior in groups of workers; however, the wide limits of agreement suggest caution in estimating individuals' sitting time with high precision. Using self-reported measures to capture patterns of workplace sitting (such as breaks in sitting time) requires further development.

Asunto(s)

Descanso , Conducta Sedentaria , Autoinforme , Encuestas y Cuestionarios , Lugar de Trabajo/estadística & datos numéricos , Adolescente , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Adulto Joven

RESUMEN

CONTEXT: To systematically review and provide an informative synthesis of findings from longitudinal studies published since 1996 reporting on relationships between self-reported sedentary behavior and device-based measures of sedentary time with health-related outcomes in adults. EVIDENCE ACQUISITION: Studies published between 1996 and January 2011 were identified by examining existing literature reviews and by systematic searches in Web of Science, MEDLINE, PubMed, and PsycINFO. English-written articles were selected according to study design, targeted behavior, and health outcome. EVIDENCE SYNTHESIS: Forty-eight articles met the inclusion criteria; of these, 46 incorporated self-reported measures including total sitting time; TV viewing time only; TV viewing time and other screen-time behaviors; and TV viewing time plus other sedentary behaviors. Findings indicate a consistent relationship of self-reported sedentary behavior with mortality and with weight gain from childhood to the adult years. However, findings were mixed for associations with disease incidence, weight gain during adulthood, and cardiometabolic risk. Of the three studies that used device-based measures of sedentary time, one showed that markers of obesity predicted sedentary time, whereas inconclusive findings have been observed for markers of insulin resistance. CONCLUSIONS: There is a growing body of evidence that sedentary behavior may be a distinct risk factor, independent of physical activity, for multiple adverse health outcomes in adults. Prospective studies using device-based measures are required to provide a clearer understanding of the impact of sedentary time on health outcomes.

Asunto(s)

Estado de Salud , Actividad Motora , Conducta Sedentaria , Adulto , Humanos , Estudios Longitudinales , Obesidad/epidemiología , Obesidad/etiología , Factores de Riesgo , Televisión , Factores de Tiempo , Aumento de Peso

RESUMEN

PURPOSE OF REVIEW: Prolonged sitting (sedentary behavior) has deleterious cardiovascular and metabolic correlates; however, little is known about the associations of too much sitting with all-cause and cardiovascular mortality risk. In addition to the adverse effects of total sitting time, the manner in which it is accumulated has also been postulated to be important for cardiovascular health. RECENT FINDINGS: We describe recent evidence from several research papers published in the last 12-18 months, showing deleterious relationships of sedentary behavior with mortality outcomes. We also explore emerging findings on breaking up sedentary time and its potential beneficial impact on cardiovascular health. SUMMARY: Consistent independent associations have been observed between sitting time/sedentary behaviors and elevated all-cause and cardiovascular disease mortality risk. Generally, these associations have persisted following adjustment for physical activity. Furthermore, total sedentary time (measured objectively via accelerometer) is detrimentally associated with several cardiovascular risk factors, whereas breaking up sedentary time (independent of total sedentary time and moderate-to-vigorous intensity activity) is beneficially associated. This evidence provides further support to the importance of avoiding prolonged, uninterrupted periods of sitting time for cardiovascular health. However, further evidence from intervention trials is required to establish the causal pathways.

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Enfermedad Coronaria/mortalidad , Conducta Sedentaria , Humanos , Factores de Riesgo , Factores de Tiempo

RESUMEN

CONTEXT: Emerging evidence suggests that sedentary behavior (i.e., time spent sitting) may be negatively associated with health. The aim of this study was to systematically review the evidence on associations between occupational sitting and health risks. EVIDENCE ACQUISITION: Studies were identified in March-April 2009 by literature searches in PubMed, PsycINFO, CENTRAL, CINAHL, EMBASE, and PEDro, with subsequent related-article searches in PubMed and citation searches in Web of Science. Identified studies were categorized by health outcome. Two independent reviewers assessed methodologic quality using a 15-item quality rating list (score range 0-15 points, higher score indicating better quality). Data on study design, study population, measures of occupational sitting, health risks, analyses, and results were extracted. EVIDENCE SYNTHESIS: 43 papers met the inclusion criteria (21% cross-sectional, 14% case-control, 65% prospective); they examined the associations between occupational sitting and BMI (n=12); cancer (n=17); cardiovascular disease (CVD, n=8); diabetes mellitus (DM, n=4); and mortality (n=6). The median study-quality score was 12 points. Half the cross-sectional studies showed a positive association between occupational sitting and BMI, but prospective studies failed to confirm a causal relationship. There was some case-control evidence for a positive association between occupational sitting and cancer; however, this was generally not supported by prospective studies. The majority of prospective studies found that occupational sitting was associated with a higher risk of DM and mortality. CONCLUSIONS: Limited evidence was found to support a positive relationship between occupational sitting and health risks. The heterogeneity of study designs, measures, and findings makes it difficult to draw definitive conclusions at this time.

Asunto(s)

Enfermedades Profesionales/fisiopatología , Ocupaciones , Postura , Animales , Enfermedades Cardiovasculares/etiología , Diabetes Mellitus/etiología , Humanos , Neoplasias/etiología , Enfermedades Profesionales/etiología , Enfermedades Profesionales/mortalidad , Proyectos de Investigación , Factores de Riesgo , Factores de Tiempo

RESUMEN

OBJECTIVE: We examined the associations of sitting time and television (TV) viewing time with continuously measured biomarkers of cardio-metabolic risk in Australian adults. RESEARCH DESIGN AND METHODS: Waist circumference, BMI, resting blood pressure, triglycerides, HDL cholesterol, fasting and 2-h postload plasma glucose, and fasting insulin were measured in 2,761 women and 2,103 men aged > or =30 years (mean age 54 years) without clinically diagnosed diabetes from the 2004-2005 Australian Diabetes, Obesity and Lifestyle (AusDiab) study. Multivariate linear regression analyses examined associations of self-reported sitting time and TV viewing time (hours per day) with these biomarkers, adjusting for potential confounding variables. RESULTS: For both women and men, sitting time was detrimentally associated with waist circumference, BMI, systolic blood pressure, fasting triglycerides, HDL cholesterol, 2-h postload plasma glucose, and fasting insulin (all P < 0.05), but not with fasting plasma glucose and diastolic blood pressure (men only). With the exception of HDL cholesterol and systolic blood pressure in women, the associations remained significant after further adjustment for waist circumference. TV viewing time was detrimentally associated with all metabolic measures in women and all except HDL cholesterol and blood pressure in men. Only fasting insulin and glucose (men only) remained deleteriously associated with TV viewing time after adjustment for waist circumference. CONCLUSIONS: In women and men, sitting time and TV viewing time were deleteriously associated with cardio-metabolic risk biomarkers, with sitting time having more consistent associations in both sexes and being independent of central adiposity. Preventive initiatives aimed at reducing sitting time should focus on both nonleisure and leisure-time domains.

Asunto(s)

Cardiopatías/epidemiología , Actividades Recreativas/clasificación , Obesidad/epidemiología , Conducta Sedentaria , Televisión , Adulto , Australia/epidemiología , Glucemia/análisis , Índice de Masa Corporal , HDL-Colesterol/sangre , Diabetes Mellitus/epidemiología , Diabetes Mellitus/genética , Empleo/estadística & datos numéricos , Ejercicio Físico , Ayuno , Femenino , Cardiopatías/sangre , Humanos , Estilo de Vida , Lípidos/sangre , Masculino , Persona de Mediana Edad , Obesidad/etiología , Sístole/fisiología , Triglicéridos/sangre , Circunferencia de la Cintura

RESUMEN

Females perform better in certain memory-related tasks than males. Sex differences in cognitive performance may be attributable to differences in circulating oestrogen acting on oestrogen beta receptors (ERbeta) which are prevalent in brain regions such as the hippocampus, frontal lobe and cortex that mediate cognitive functions. Since soya isoflavones are known to activate ERbeta, chronic isoflavone supplementation in males may improve cognitive performance in memory-related tasks. A 12-week double-blind, placebo-controlled cross-over trial was conducted in thirty-four healthy men to investigate the effect of isoflavone supplementation on cognitive function. Volunteers were randomised to take four capsules/d containing soya isoflavones (116 mg isoflavone equivalents/d: 68 mg daidzein, 12 mg genistein, 36 mg glycitin) or placebo for 6 weeks, and the alternate treatment during the following 6 weeks. Assessments of memory (verbal episodic, auditory and working), executive function (planning, attention, mental flexibility) and visual-spatial processing were performed at baseline and after each treatment period. Isoflavone supplementation significantly improved spatial working memory (P = 0.01), a test in which females consistently perform better than males. Compared with placebo supplementation, there were 18 % fewer attempts (P = 0.01), 23 % fewer errors (P = 0.02) and 17 % less time (P = 0.03) required to correctly identify the requisite information. Isoflavones did not affect auditory and episodic memory (Paired Associate Learning, Rey's Auditory Verbal Learning Task, Backward Digit Span and Letter-Number Sequencing), executive function (Trail Making and Initial Letter Fluency Task) or visual-spatial processing (Mental Rotation Task). Isoflavone supplementation in healthy males may enhance cognitive processes which appear dependent on oestrogen activation.

Asunto(s)

Suplementos Dietéticos , Glycine max , Isoflavonas/farmacología , Memoria a Corto Plazo/efectos de los fármacos , Adulto , Anciano , Anciano de 80 o más Años , Cognición/efectos de los fármacos , Estudios Cruzados , Método Doble Ciego , Humanos , Masculino , Recuerdo Mental/efectos de los fármacos , Persona de Mediana Edad , Pruebas Neuropsicológicas

RESUMEN

BACKGROUND: Health claims link soy protein (SP) consumption, through plasma cholesterol reduction, to a decreased risk of heart disease. Soy isoflavones (ISOs), particularly in individuals who produce equol, might also contribute to lipid lowering and thus reduce SP requirements. OBJECTIVE: The objective was to examine the contributions of SP, ISOs, and equol to the hypocholesterolemic effects of soy foods. DESIGN: Nonsoy consumers (33 men, 58 women) with a plasma total cholesterol (TChol) concentration >5.5 mmol/L participated in a double-blind, placebo-controlled, crossover intervention trial. The subjects consumed 3 diets for 6 wk each in random order, which consisted of foods providing a daily dose of 1) 24 g SP and 70-80 mg ISOs (diet S); 2) 12 g SP, 12 g dairy protein (DP), and 70-80 mg ISOs (diet SD); and 3) 24 g DP without ISOs (diet D). Fasting plasma TChol, LDL cholesterol, HDL cholesterol, and triglycerides (TGs) were measured after each diet. RESULTS: TChol was 3% lower with the S diet (-0.17 +/- 0.06 mmol/L; P < 0.05) than with the D diet, and TGs were 4% lower with both the S (-0.14 +/- 0.05 mmol/L; P < 0.05) and SD (-0.12 +/- 0.05 mmol/L; P < 0.05) diets. There were no significant effects on LDL cholesterol, HDL cholesterol, or the TChol:HDL cholesterol ratio. On the basis of urinary ISOs, 30 subjects were equol producers. Lipids were not affected significantly by equol production. CONCLUSIONS: Regular consumption of foods providing 24 g SP/d from ISOs had no significant effect on plasma LDL cholesterol in mildly hypercholesterolemic subjects, regardless of equol-producing status.

Asunto(s)

LDL-Colesterol/sangre , Colesterol/sangre , Hipercolesterolemia/dietoterapia , Isoflavonas/administración & dosificación , Alimentos de Soja , Proteínas de Soja/administración & dosificación , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Biomarcadores/sangre , Biomarcadores/metabolismo , Biomarcadores/orina , HDL-Colesterol/sangre , Estudios Cruzados , Método Doble Ciego , Equol , Femenino , Humanos , Hipercolesterolemia/sangre , Hipercolesterolemia/metabolismo , Isoflavonas/metabolismo , Isoflavonas/orina , Masculino , Persona de Mediana Edad , Alimentos de Soja/análisis , Proteínas de Soja/metabolismo , Triglicéridos/sangre

RESUMEN

BACKGROUND: This study evaluated the dose-response effects of alpha-cyclodextrin, a cyclic oligosaccharide, on the glycaemic and insulinaemic responses to the consumption of a standard carbohydrate meal. METHODS: In a double-blind, randomised, cross-over design, 10 healthy subjects consumed boiled white rice containing 50 g of digestible carbohydrate to which 0 (control), 2, 5 or 10 g of alpha-cyclodextrin was added. Plasma glucose and insulin concentrations were determined prior to and for 2 h after consumption of each meal. RESULTS: The area under the plasma glucose curve was negatively related to the dose of alpha-cyclodextrin (r(2)=0.97, p=0.02), with the areas being significantly reduced at the 5- and 10-gram doses compared with the control (p<0.05). alpha-Cyclodextrin did not affect the area under the plasma insulin curve (p=0.39). Higher doses of alpha-cyclodextrin resulted in greater satiety, but were associated with reduced palatability and an increased incidence of minor gastrointestinal complaints (stomach ache, nausea, bloating). CONCLUSION: alpha-Cyclodextrin reduces the glycaemic response to a standard carbohydrate meal in a dose-dependent manner and may be useful as an ingredient for reducing the glycaemic impact of such foods.

Asunto(s)

Glucemia/análisis , Carbohidratos de la Dieta/farmacocinética , Índice Glucémico/efectos de los fármacos , Insulina/sangre , alfa-Ciclodextrinas/farmacología , Adulto , Área Bajo la Curva , Glucemia/metabolismo , Estudios Cruzados , Relación Dosis-Respuesta a Droga , Método Doble Ciego , Femenino , Humanos , Masculino , Periodo Posprandial , Respuesta de Saciedad/efectos de los fármacos , Gusto/efectos de los fármacos , alfa-Ciclodextrinas/administración & dosificación , alfa-Ciclodextrinas/efectos adversos