P124 Chronotype and OSA combine to modify risk of hypertension

INTRODUCTION: There are limited data on the association of chronotype and hypertension and on their interaction on hypertension. This study aimed to investigate the independent and combined effects of chronotype and OSA on risk for prevalent hypertension in a middle-aged community population. METHODS: Baseline data on adult participants (n=1098, female=58%; age mean [range]=56.7[40.8–80.6] years) from an Australian community cohort study were analysed. Shift workers and individuals with incomplete data were excluded. Prevalent hypertension was defined as ‘doctor diagnosed’ and/or an elevated average systolic blood pressure (BP; ≥140mmHg) or diastolic BP (≥90mmHg). OSA was diagnosed when apnoea hypopnoea index (AHI) ≥10 events/hour from in-laboratory polysomnography. Chronotype was determined from actigraphy mid-sleep time on work free days. Tertiles of mid-sleep time were used to categorise morning, intermediate and evening chronotypes. Logistic regression (adjusted for sex, body mass index, age, alcohol consumption and sleep duration) were used to assess the cross-sectional relationship between chronotype, OSA and hypertension. RESULTS: After applying exclusion criteria 496 participants were analysed (female=58%; age mean[range]=57.0[42.1–81.6] years). All those with OSA had greater odds of hypertension than those without and there was no difference in risk of hypertension according to chronotype. Compared to morning chronotypes with no OSA (n=84), evening chronotypes with OSA (n=79) had non-significantly increased odds (OR 2.15, 95% CI 1.00–4.76; P=0.054) for hypertension while morning chronotypes with OSA (n=82) had significantly increased odds (OR 3.02, 95% CI 1.44–6.58; P=0.004). DISCUSSION: Morning chronotypes with OSA might be at increased risk of hypertension compared to evening chronotypes with OSA.