Effects of long-term average temperature and temperature variability on cardiovascular disease hospitalizations in the US Medicare population

Abstract

BACKGROUND AND AIM: Numerous studies have shown short-term exposure to extreme temperature is associated with increased mortality and morbidity. Less is known about effects of long-term exposure to warm or cold temperatures. Our aim was to evaluate associations of long-term temperature exposure and temperature variability with cardiovascular disease (CVD) hospitalizations. METHODS: We constructed an open cohort consisting of all fee-for-service Medicare beneficiaries, aged ≥65, living in the contiguous US from 2000 through 2016 (~63 million individuals). We used data from the 4km Gridded Surface Meteorological dataset to assess the annual (January-December), summer (June-August), and winter (December-February) average temperature and temperature variability (standard deviation) for each year for each zip code. Cox-equivalent Poisson models were used to estimate associations with first CVD, coronary heart disease (CHD) or cerebrovascular disease (CBV) hospitalization, after adjustment for potential confounders (including individual and area-level SES indicators). RESULTS:Higher annual average and summer average temperatures were associated with an increased risk of CVD, CHD and CBV hospitalization. Lower winter average temperatures were associated with an increased risk of CVD and CHD hospitalization, but a decreased risk of CBV hospitalization. For CVD hospitalization, we found a HR of 1.07 (95%CI: 1.06, 1.07) per IQR increase (8.1°C) for annual average temperature, a HR of 1.03 (95%CI: 1.03, 1.04) per IQR increase (5.2°C) for summer average temperature, and a HR of 0.97 (95%CI: 0.97, 0.98) per IQR increase (11.7°C) for winter average temperature. Higher annual and winter temperature variability and lower summer temperature variability were associated with an increased risk for all outcomes. Associations were modified by age, race, air pollution and greenness. CONCLUSIONS:Warmer annual and summer average temperatures and cooler winter average temperatures were associated with an increased risk of CVD hospitalizations. Higher annual and winter temperature variability and lower summer temperature variability were also associated with increased risk. KEYWORDS: temperature, temperature variability, Cardiovascular diseases