A cohort study of seasonality and weather-sensitivity of chronic disease biomarkers in the tropics: the Costa Rican Longevity and Healthy Aging Study (CRELES).

<ns3:p>Background Previous research has shown seasonality and climate-sensitivity in chronic disease biomarkers, but it hasn’t been done in tropical settings with different weather patterns. Identifying these variations can help understand the potential health consequences of global climate change. Our objective is to find seasonal variations in 13 biomarkers and their association with ambient heat and pluviosity in a tropical environment. Methods We studied within-person changes in 13 biomarkers between two measures 1.8 years apart in a nationally representative panel of 2,177 older adults in Costa Rica. We used NASA’s global databases for ambient heat and precipitation in the month previous and location of participants. To find seasonal patterns, we used sinusoidal regression, and “fixed effects” regression models for robust associations. Results The amplitude of seasonality was significant in ten of the 13 biomarkers. Total cholesterol had the widest amplitude, with a peak in late July and a trough in early December. Rainfall in the previous month didn’t show a significant association, but seven biomarkers were associated with ambient temperature. Warmer weather was linked to significant increases in total cholesterol, fasting blood glucose, creatinine, and DHEAS, and decreases in hemoglobin A1c, abdominal circumference, and telomere length. Weather variation accounted for the entirety of the seasonal variation in creatinine, DHEAS, and systolic blood pressure. Conclusion This study found significant seasonality in most biomarkers and association with ambient in a tropical environment. Research in other populations will inform generalizability, the importance of unmeasured seasonal and weather-related confounding in population-based risk factor research, and causal estimation of climate change effects on health. Extrapolating ambient heat effects, a 2°C global temperature rise by 2050 would increase total cholesterol by 7% (11% in urban areas), elevate serum creatinine by 6%, and reduce telomere length by 4%.</ns3:p>