Ambient temperature and prevalence of diabetes and insulin resistance in the Spanish population. Di@bet.es study.

Objective: The activity of brown adipose tissue is sensitive to changes in ambient temperature. A lower exposure to cold could result in an increased risk of developing diabetes at population level, although this factor has not yet been sufficiently studied. Design: We studied 5072 subjects, participants in a national, cross-sectional population-based study representative of the Spanish adult population (Di@bet.es study). All subjects underwent a clinical, demographic and lifestyle survey, a physical examination and blood sampling (75 g oral glucose tolerance test). Insulin resistance was estimated with the homeostasis model assessment (HOMA-IR). The mean annual temperature (degrees C) in each individual municipality was collected from the Spanish National Meteorology Agency. Results: Linear regression analysis showed a significant positive association between mean annual temperature and fasting plasma glucose (beta: 0.087, P < 0.001), 2 h plasma glucose (beta: 0.049, P = 0.008) and HOMA-IR (beta: 0.046, P = 0.008) in multivariate adjusted models. Logistic regression analyses controlled by multiple socio-demographic variables, lifestyle, adiposity (BMI) and geographical elevation showed increasing odds ratios for prediabetes (WHO 1999), ORs 1, 1.26 (0.95-1.66), 1.08 (0.81-1.44) and 1.37 (1.01-1.85) P for trend = 0.086, diabetes (WHO 1999) ORs 1, 1.05 (0.79-1.39), 1.20 (0.91-1.59) and 1.39 (1.02-1.90) P = 0.037, and insulin resistance (HOMA-IR >= 75th percentile of the non-diabetic population): ORs 1, 1.03 (0.82-1.30), 1.22 (0.96-1.55), 1.26 (0.98-1.63) (P for trend = 0.046) as the mean annual temperature (into quartiles) rose. Conclusions: Our study reports an association between ambient temperature and the prevalence of dysglycemia and insulin resistance in Spanish adults, consistent with the hypothesis that a lower exposure to cold could be associated with a higher risk of metabolic derangements.