Associations of Outdoor Temperature, Bright Sunlight, and Cardiometabolic Traits in Two European Population-Based Cohorts

Abstract

Seasonal variation in cold and light exposure may influence metabolic health. Objective: We assessed the associations of bright sunlight and outdoor temperature with measures of glucose and lipid metabolism in two populations of middle-aged European subjects. Design: Cross-sectional study. Setting: Two population-based European cohorts. Participants: Middle-aged nondiabetic subjects from the Oxford Biobank (OBB; N 5 4327; mean age, 41.4 years) and the Netherlands Epidemiology of Obesity (NEO) study (N55899;mean age, 55.6 years). Interventions: Data on outdoor bright sunlight and temperature collected from local weather stations. Main Outcome Measures: Insulin resistance and fasting lipid levels. Multivariable regression analyses were adjusted for age, sex, percentage body fat, season, and either outdoor temperature or bright sunlight. Results: In the OBB cohort, increased bright sunlight exposure was associated with lower fasting insulin [21.27% (95% CI, 22.09 to 20.47%) per extra hour of bright sunlight], lower homeostatic model assessment for insulin resistance (21.36%; 95% CI, 22.23 to 20.50), lower homeostatic model assessment for b-cell function (20.80%; 95% CI, 21.31 to 20.30), and lower triglyceride (21.28%; 95% CI, 22.07 to 20.50) levels. In the NEO cohort generally unidirectional but weaker associations were observed. No associations between outdoor temperature and measures of glucose or lipid metabolism were detected following adjustment for bright sunlight.