Is the chronotype associated with obstructive sleep apnea?

Chronotype and obstructive sleep apnea (OSA) appear to have a similar lifelong evolution, which could indicate a possible effect of morningness or eveningness in the apnea-hypopnea index (AHI). The present study aimed to examine the prevalence of chronotypes in a representative sample of So Paulo city residents and to investigate the effect of chronotypes on the severity of OSA. We performed a cross-sectional analysis using the So Paulo Epidemiologic Sleep Study (EPISONO). All participants underwent a full-night polysomnography and completed the Morningness-eveningness, Epworth Sleepiness Scale, and UNIFESP Sleep questionnaires. Chronotypes were classified as morning-type, evening-type, and intermediate. Morning-type individuals represented 52.1 % of the sample, followed by intermediate (39.5 %), and evening-type (8.4 %) individuals. After stratifying the sample by body mass index (BMI) (> 26.8 kg/m(2)) and age (> 42 years), we observed increased AHI values in morning- and evening-type individuals. We demonstrated, for the first time, an age- and BMI-related effect of morning- and evening-types in OSA severity, suggesting that the intermediate chronotype might play a role as a protective factor in older and overweight patients.