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BACKGROUND: Exposure to cold reportedly increases musculoskeletal pains. We assessed the prevalence of such pain and self-reported threshold temperature (TT) at which the pain emerges. METHODS: A random sample of 6591 people in Finland, aged 25-74 years, answered a questionnaire on repeated cold-related musculoskeletal pain (CMP) and its TT. The response rate was 64%. We used quantile regression to quantify the effects of personal characteristics and region of residence on TT at various locations of its distribution. RESULTS: Of the participants, 1892 (30%) experienced CMP in at least one body site and 1692 reported TT. Ten percent of the participants who perceived CMP did so at -2 °C, 50% at -14 °C and 90% at -23 °C. Residence in the South elevated TT by 1-6 °C compared with residence in the North, depending on the proportion of participants reporting CMP at various temperatures. Joint disorders increased TT at milder temperatures, at which only 10% of all participants perceived CMP, whereas back disorders did so mainly at lower temperatures, at which 70% were affected. Overweight was associated with a 2 °C lower TT, and physical inactivity with a 1 °C higher TT, and TT increased by 1 °C per 10-year increase in age. The greatest model-estimated difference in median TT between subgroups was 12 °C. CONCLUSIONS: People suffering from musculoskeletal disorders and those living in the warmer areas of Finland need special advice to protect themselves against the cold. Our study provides preliminary information to support such advice.

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OBJECTIVE: To determine the prevalence of cold-related symptoms among the general population, especially people with pre-existing diseases. STUDY DESIGN: Six thousand nine hundred and fifty-one men and women aged 25-74 years, who had participated in the National FINRISK 2002 Study, filled in a questionnaire on cold-related symptoms. METHODS: Age-specific and age-adjusted prevalence figures for cold-related symptoms were calculated. The symptoms were regressed for gender, age, region of residence, industry, self-reported disease and smoking. RESULTS: Five percent of the subjects reported chest pain or arrhythmia in the cold, and higher prevalence figures were found for respiratory (men 26%/women 31%) and musculoskeletal symptoms (31%/28%). The prevalence of cold-related cardiovascular symptoms was particularly high among subjects with coronary heart disease (33%/46%) or cardiac insufficiency (25%/40%), as was the prevalence of respiratory symptoms among asthmatics (69%/78%) and subjects with chronic bronchitis (66%/77%). The symptoms increased with age, were more common in colder areas than milder areas, and were more common in those engaged in agricultural work than those engaged in industry or services. Cold-related cardiovascular and respiratory symptoms were more common among women than men. The regression-adjusted contributions (percentage points) to various cold-related symptoms were 2-45% for lung disease, 7-9% for cardiovascular disease, 3-15% for joint or back disease and 6-13% for mental disease. CONCLUSIONS: Large proportions of people living in the north, particularly those with pre-existing medical conditions, experience cardiovascular, respiratory or musculoskeletal symptoms in the cold. Since the symptoms may predict future morbidity and mortality, a strategy is needed to reduce the cold-related health risks of the entire population.

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This review presents hormonal responses to various cold exposures and their calorigenic effects in man and some animals. Previous studies in rats have shown that cold exposures activate the hypothalamic-pituitary-thyroid axis. Increased thyroid hormone concentrations lead to heat production via general stimulation of metabolism (obligatory thermogenesis) and possibly via activation of thyroid hormone receptors and uncoupling protein 1 (UCP 1) and deiodinase enzyme genes in the brown adipose tissue (BAT). In human subjects long-term cold exposures do not seem to activate the pituitary-thyroid axis, but rather accelerate the elimination of triiodothyronine (T3), leading to low serum concentrations of free T3 hormone. In corollary to this a hypothyreotic condition with increased serum thyroid-stimulating hormone and impaired mood and cognitive performance can be observed after long-term cold exposures such as wintering. During cold exposures the sympathetic nerve system is activated and noradrenaline is released to blood circulation and to BAT, where it leads to production of cAMP, lipolysis and free fatty acids. Free fatty acids open the mitochondrial proton channel protein in BAT. Protons enter the mitochondria and inhibit ATP synthesis (uncoupling). By this way energy is transformed into heat (facultatory or adaptive thermogenesis). In adult human subjects the amount of BAT is small and adaptive thermogenesis (non-shivering thermogenesis) has a smaller role. UCP 1 with other uncoupling proteins may have other functions in the control of body weight, sugar balance and formation of reactive oxygen species.

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Paraoxonase (PON) is an antioxidative enzyme, which eliminates lipid peroxides. The mutation in codon 55 of PON1 gene causes a change of methionine (M-allele) to leucine (L-allele) and influences PON activity. The Saami are a population living in the northern part of Fennoscandia. In previous studies their death rate from coronary artery disease (CAD) was found to be low. We compared PON M/L55 allele frequencies of 68 Saami and 68 Finnish men and related the PON genotypes to plasma lipid levels and to the levels of autoantibodies against oxidized LDL. The M/L55 genotypes were determined by PCR and restriction enzyme digestion. ELISA was used to measure antibodies against oxidized LDL. The L- and M-allele frequencies were 64% and 36% in Saami population and 64% and 36% in Finnish men, respectively (p = NS, Fisher's exact test). There were also no significant differences in plasma lipid levels or in antibody levels against oxidized LDL between PON genotypes or between Saami and Finnish men. Our results indicate that the PON M/L55 genotype is not associated with plasma lipid levels or the levels of autoantibodies against oxidized LDL in these populations. The Saami men have the same PON M/L55 allele distribution as the Finnish men and the PON genotype might thus not be one factor protecting Saami against CAD.

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Patients with Raynaud's phenomenon (RP) have abnormal digital vasoconstriction in response to cold. The aim of the study was to investigate the effects of cooling on sensory perception and manual performance in healthy male subjects and subjects with RP. There were two groups of subjects with primary RP: 12 subjects fulfilled the criteria of Lewis (L) and the other 12 the more critical criteria of Maricq (M). Control group (C) consisted of 19 healthy men. Subjects were exposed to 5 degrees C for 60 min. Skin temperatures were measured. Finger dexterity, pinch strength, abduction/adduction of fingers, pressure perception threshold and vibration perception threshold were tested during the exposure every 15 min. At the beginning of the exposure the mean (S.E.) finger temperature was 2.5 (1.2) degrees C (P<0.05) lower in M than in C. Manual performance and sensory perception were impaired due to the cooling, the impairment being significantly greater in M than in C. Responses of L were between those of M and C. In a given finger temperature vibration and pressure sensibility and manual performance were lower in M and L than in C. In conclusion, cold exposure decreased sensory perception and manual performance in the subjects with RP to a lower level than in the healthy subjects. Non-thermal factors may also decrease performance in RP.

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In order to evaluate the effects of climatic factors on the secretion of thyroid hormones and TSH in a high latitude population, we have taken serum and urine samples from 20 healthy men from northern Finland (67 degrees -68 degrees N) every 2 months for a period of 14 months. Serum free triiodothyronine (T(3)) levels were lower in February than in August (3.9 vs 4.4 pmol/l, P<0.05) and TSH levels were higher in December than during other months (2.1 vs 1.5-1.7 mU/l, P<0.01). Serum total and free thyroxine (T(4)), total T(3) and reverse T(3) levels and urinary T(4) levels were unchanged. Urinary T(3) levels were significantly higher in winter than in summer. Serum free T(3) correlated highly significantly with the outdoor temperature integrated backwards weekly for 7-56 days (r=0.26 for 1-56 days) from the day when the blood samples were taken. Serum TSH did not show any significant correlation with the thyroid hormones or with the integrated temperature of the previous days, but it did show an inverse and significant correlation (r=-0.31) with the ambient luminosity integrated backwards for 7 days from the day when the blood sample was taken. The gradually increasing correlation between outdoor temperatures and serum free T(3) suggests that the disposal of thyroid hormones is accelerated in winter, leading to low serum free T(3) levels and a high urinary free T(3) excretion. Since there was no correlation between thyroid hormones and serum TSH, the feedback mechanism between TSH and thyroid hormones may not be the only contributing factor, and other factors such as ambient luminosity may at least partly determine serum TSH in these conditions. Also urinary free T(3) appears to be a novel and non-invasive indicator for thyroid physiology.

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We studied habituation processes by exposing six healthy men to cold air (2 h in a 10 degrees C room) daily for 11 days. During the repeated cold exposures, the general cold sensations and those of hand and foot became habituated so that they were already significantly less intense after the first exposure and remained habituated to the end of the experiment. The decreases in skin temperatures and increases in systolic blood pressure became habituated after four to six exposures, but their habituations occurred only at a few time points during the 120-min cold exposure and vanished by the end of the exposures. Serum thyroid-stimulating hormone, total thyroxine and triiodothyronine, norepinephrine, epinephrine, cortisol, and total proteins were measured before and after the 120-min cold exposure on days 0, 5, and 10. The increase in norepinephrine response became reduced on days 5 and 10 and that of proteins on day 10, suggesting that the sympathetic nervous system became habituated and hemoconcentration became attenuated. Thus repeated cold-air exposures lead to habituations of cold sensation and norepinephrine response and to attenuation of hemoconcentration, which provide certain benefits to those humans who have to stay and work in cold environments.

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We exposed six healthy men to 1-h cold air (10 degrees C) daily for 11 days and measured adrenal and thyroid hormones and TSH in serum before and after the cold air exposure on days 0, 5 and 10. We observed that on days 0, 5 and 10 the resting levels and the levels after the cold exposure in serum adrenaline, thyroid hormones and TSH did not significantly change, whereas the serum noradrenaline levels showed a significant 2.2-2.5-fold increase in response to the cold air exposures. The increases were similar indicating that the subjects did not show signs of habituation in their noradrenaline responses. Therefore the 1-h cold air exposure is not sufficiently intensive to reduce the cold-induced sympathetic response.

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BACKGROUND AND AIM: In epidemiological questionnaire studies results can be influenced by non-responder bias. However, in respiratory epidemiology this has been analysed in very few recently published papers. The aim of our paper is to assess if the results found in our previous postal questionnaire study in an adult population in Northern Finland were biased by non-response. METHODS: A random sample of 385 persons from the 1,284 non-responders in a previous postal questionnaire study was examined. The same questionnaire as in the original study was again mailed to these persons, and those still not answering were contacted by phone. RESULTS: Totally 183 complete answers (48%) were collected. Lack of interest (56%) and forgetting to mail the response letter (22%) were the most common reasons to non-response. Typical non-responders were young men and current smokers who less frequently reported respiratory symptoms in exercise and asthma than the responders in the original study. Answers collected by phone gave for some questions higher prevalence rates than postal answers. CONCLUSION: Firstly, in this population the response rate (83.6%) in the original study was high enough to provide reliable results for respiratory symptoms and diseases, only the prevalence of current smoking was biased by non-response. Secondly, the methods used for collecting responses in a non-response study may influence the results.

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Frostbites affect the civilian northern population more commonly than thought earlier. Cumulative lifetime incidences may be as high as 44-68% for all types of frostbite. Incidences of frostbite have mainly been reported in association with military activities but occur also during occupational duties and in recreational situations. Frostbites often affect the extremities and especially the head region. Several different predisposing factors have been reported in relation to frostbites. These can be divided mainly into environmental, individual, behavioural and occasion-linked factors. Actual risk analyses have been conducted for a limited amount of these predisposing factors. Frostbites very often result in different functional disadvantages, some of which can lead to a temporary or permanent disability to work or carry out military duties, while others may impact negatively on occupational activities, or cause hospitalization and invalidity to varying degrees. Further, frostbites often cause sequelae lasting from a few weeks to a lifetime.

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The aim of the study was to investigate prevalence and qualities of sequelae following moderate finger frostbite. The study material comprised 30 subjects, who had suffered second-degree frostbite (73% contact frostbite) 4-11 years before this study. In clinical tests 66% of the subjects had an elevated tendency for vasospasm, yet only 20% suffered from white fingers. However, no marked traces of frostbite-related alterations were observed in systemic cardiovascular reflex tests or in X-ray examinations of the frostbite area. Subjective assessments revealed a high prevalence of sequelae (63%), although the primary frostbite was moderate and local. The sequelae in the frostbite area included hypersensitivity to cold (53%), numbness of fingers (40%), and declined sensitivity of touch (33%). Also working ability was lowered due to frostbite sequelae (13%). In cold air provocation tests, the skin temperature of the frostbitten areas decreased more quickly and reached lower values than in healthy control subjects. In conclusion the suffered frostbite was associated with an increased tendency for vasospasm. Subjective sensations of the frostbitten area were associated with thermophysiological changes. The sequelae were reported to worsen in the cold environment thus emphasizing the probable occupational limitations of even moderate cold injury.

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BACKGROUND: Relatively few occupational epidemiological studies have been conducted concerning the association between cold ambient temperatures and cold exposure injuries, and fewer still of traumatic occupational injuries and cold ambient temperatures. METHODS: The association of ambient temperature and wind data from the National Climatic Data Center with injury data from mines reported to the Mine Safety and Health Administration (MSHA) was evaluated over a 6 year period from 1985-1990; 72,716 injuries from the seven states with the most numerous injuries were included. Temperature and wind data from each state's metropolitan weather stations were averaged for each day of the 6 year period. A weighted linear regression tested the relationship of ungrouped daily temperature and injury rate for all injury classes. For cold exposure injuries and fall injuries, relative incidence rates for grouped temperature data were fit with Poisson regression. RESULTS: As temperatures decreased, injury rates increased for both cold exposure injuries and slip and fall injuries. The association of slip and fall injuries with temperature was inverse but not strictly linear. The strongest association appeared with temperatures 29 degrees F and below. The injury rates for other accident categories increased with increasing ambient temperatures. CONCLUSIONS: This study suggests that statewide average ambient temperature reflects the expected association between the thermal environment and cold exposure injuries for workers, but more importantly, documents an association between ambient temperatures and occupational slip and fall injuries.

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Cold causes cardiopulmonary stress often perceived as shortness of breath or chest pain, and causes exacerbation of these symptoms in persons suffering heart or lung disease. We investigated the prevalence of these symptoms and their association with sex, age and cold exposure in a population-based sample of 1,785 persons who lived in three areas of Finland. The exposure to cold was measured by the annual number cold days (mean daily temperature below 0 degree C) in the resident locality and weekly hours spent in the cold in winter. Shortness of breath was 25% and chest pain 52% more common in females than in males, and their prevalence increased by 24% and 77%, respectively, for every 10 years of age. The prevalence of shortness of breath increased by 5% and chest pain by 6% for every 10 cold days in the resident locality, and by 6% and 7% for every 10 hours spent in the cold, respectively. We suggest that environmental cold, measured by the number of cold days throughout the year and weekly hours spent in the cold, may provoke cardiopulmonary symptoms independent of sex and age.

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Mortality was compared in two major towns in northern Finland (Kemi and Oulu), which according to previous studies have high and low mortalities, respectively. In 1991-1995 life expectancy at birth in Oulu exceeded the national average by 0.7 years in males and 0.4 years in females but in Kemi it fell short of the national average in both sexes by 2.5 years. The shorter life-time in Kemi resulted from a slower-than-average decline in male mortality since the 1960's and an increase in female mortality by a factor of 1/5 in 1981-1995. In the 1990's, Kemi as marked by ischaemic heart disease (excess over national mortality 10% in males, 18% in females), pneumonia among the elderly (excess 2-fold), cancer in females (excess 30%), accidents (excess 24% in males, 82% in females) and male suicides (excess 76%), most of which in Oulu were below the national figures. Surveys are underway to clarify reasons for this mortality difference between the two towns.

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Helicobacter pylori causes a chronic gastric infection, which has been associated with coronary heart disease. To evaluate the mechanisms of this association, we studied whether the infection affects serum lipid levels as previously shown in acute infections. We analysed the serum samples of 880 males who participated in a reindeer herders' health survey in Northern Finland in 1989. H. pylori IgG and IgA antibodies were measured by enzyme-linked immunosorbent assay and triglyceride, total cholesterol and high-density lipoprotein cholesterol concentrations by routine enzymatic methods. A total of 52% of the subjects were positive for both H. pylori specific IgG and IgA and 31% were antibody-negative. The serum triglyceride and total cholesterol concentrations were significantly higher in the males with positive IgG and IgA antibody titres for H. pylori than in the males with no signs of infection (1.20 vs. 1.03 mmol/l, P < 0.001 and 6.59 vs. 6.11 mmol/l, P < 0.001, respectively). The associations remained statistically significant in non-smokers after the adjustment for age, body mass index (BMI) and social class. The finding supports the hypothesis that chronic infections may modify the serum lipid profile in a way that increases the risk of atherosclerosis.

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Apolipoprotein A-IV (apoA-IV) is a glycoprotein constituent of triglyceride-rich and high-density lipoproteins (HDL) and may thus play an important role in lipid metabolism. In Finland two common isoforms (A-IV-1 and A-IV-2) of apoA-IV have been found. The isoforms are the result of the G to T substitution in the third base of the codon 360 in the apoA-IV-2 allele of the apoA-IV gene. The purpose of the study was to determine the apoA-IV allele frequencies in the Saami and the Finns, and to relate the apoA-IV phenotypes to serum lipids. The sample was drawn in connection with a Reindeer Herders' Health Survey performed in northern Finland in 1989. The study group included 248 men with known ethnic origin, Saami and Finns, who lived in the area of the nine northernmost municipalities of Finland. ApoA-IV phenotypes from 71 Saami (both parents Saami) and 177 Finns (both parents Finns) were determined by isoelectric focusing and Western blotting. Serum lipids were determined enzymatically. ApoA-IV allele frequencies in the Saami and the Finns were for A-IV-1 0.894 vs 0.944 and for A-IV-2 0.106 vs 0.056, respectively (chi2-test, P < 0.05). The effect of the apoA-IV phenotype on serum HDL-cholesterol levels differed significantly between the Saami and the Finns (two-way ANCOVA, interaction between ethnicity and apoA-IV phenotype, P < 0.02). In the Saami, HDL-cholesterol levels were significantly higher in the apoA-IV-2/1 than in the apoA-IV-1/1 phenotypes (ANCOVA, P < 0.05). Mean total cholesterol, low-density lipoprotein (LDL)-cholesterol, apolipoprotein B, HDL-cholesterol and triglyceride levels did not differ statistically significantly between the Saami and the Finns. Yet, there was a trend in the Saami of having higher mean total cholesterol, LDL-cholesterol and apolipoprotein B levels than the Finns among the apoA-IV-2/1 phenotypes, while there was only a small difference in these parameters between the Saami and the Finns among the apoA-IV-1/1 phenotypes. In conclusion, the Saami have a higher frequency of the apoA-IV-2 allele than the Finns and most of the other studied populations.

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Chronic Chlamydia pneumoniae infection has been associated with atherosclerosis by seroepidemiological studies. Further, acute bacterial infections are known to influence lipid metabolism. To clarify the possible pathogenetic mechanisms of this association, we studied serum lipids and the C. pneumoniae IgG antibody titers of 1,053 males who participated in the reindeer herders health survey in Northern Finland in 1986-1989. The mean age of the study group was 47 years (range 20-87). When comparing nonsmoking C. pneumoniae antibody-positive (IgG > or = 32) subjects to those with no antibodies, the age-adjusted mean concentration of triglycerides was increased (1.34 vs. 1.04 mmol/l; p = 0.03) and high-density lipoprotein (HDL) was decreased (1.24 vs. 1.35 mmol/l; p < 0.001). HDL:total cholesterol ratio was also decreased (0.20 vs. 0.23; p = 0.01). In smokers changes were very similar, but not statistically significant. Thus, C. pneumoniae antibodies seem to correlate with an altered serum lipid profile considered to increase the risk of atherosclerosis. This finding supports the proposal that infections, in this case C. pneumoniae infection, may play a role in the pathogenesis of atherosclerosis.

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To evaluate the seasonal influence upon thyroid hormone dynamics, we took blood samples every two months during a period of 14 months from 20 healthy males living in Northern Finland (69-70 degrees N), where the mean daily temperature ranges from a winter minimum of -40 degrees C to a summer maximum of 2 degrees C, while the photoperiod changes from a polar night of 6 days in winter to a polar day of 45 days in summer. The subjects were allowed free choice of diet, exercise, and outdoor exposure. Serum free T3 levels were lower in February than in August (3.9 vs. 4.4 pmol/l, p < 0.05) and TSH levels higher in December than during other months (2.1 vs. 1.5-1.7 mU/l, p < 0.05). Serum total and free T4 and total T3 levels were unchanged. Serum free T3 correlated significantly to the mean outdoor temperature of the preceding month. Serum TSH did not show any correlation with the mean temperature of the month or with free T3. Low serum free T3 in winter suggests that the disposal of thyroid hormones is accelerated in cold as described in the Polar T3 Syndrome. Elevations in serum TSH are not accounted for by changes in circulating thyroid hormones, suggesting that other influences, such as photoperiod, may mediate this fluctuation.

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