RESUMEN
AIMS: Although both chronic low back pain (cLBP) and sleep problems are prevalent among active workers, the relation between these variables is not well established. This study aimed to examine the bidirectional association between cLBP and sleep in schoolteachers. METHODS: The Pittsburgh Sleep Quality Index (PSQI) and cLBP were self-reported by 530 schoolteachers in Londrina, Brazil, at baseline and after 2 years of follow-up. Generalized estimating equations were adjusted for sociodemographic, lifestyle and mental health variables. RESULTS: Poor sleep quality at baseline was associated with cLBP at follow-up after adjusting for sociodemographic and lifestyle variables (OR=1.61; 95% confidence interval [95% CI]=1.06, 2.47). Changes in the PSQI score over time were also associated with a higher likelihood of cLBP at follow-up (OR=1.13; 95% CI=1.07, 1.20 for each 1-point increase in the PSQI score), regardless of mental health condition. cLBP at baseline was associated with worse sleep quality at follow-up after adjusting for sociodemographic and lifestyle variables (OR=1.56; 95% CI=1.02, 2.37). The presence of cLBP also changed the PSQI score over time (ß coefficient=1.153; 95% CI=0.493, 1.814). CONCLUSIONS: Worse sleep quality was prospectively and bidirectionally associated with cLBP. Concretely, changes in PSQI values after 2 years of follow-up increased the likelihood of reporting cLBP, and baseline cLBP was associated with sleep quality worsening (i.e., higher score in the PSQI). Mental health conditions such as self-rated health, depression and anxiety play a relevant confounding role in the bidirectional associations between sleep and chronic low back pain.