Heat and Hospital Admissions in 43 US Cities

Abstract

ISEE-424 Objective: To better understand health consequences of climate change and variability by studying heat and hospital admissions among elderly people. Material and Methods: We obtained daily counts of nonelective hospital admissions for cardiovascular disease (CVD), diabetes, pneumonia, chronic obstructive pulmonary disease (COPD), and myocardial infarction (MI)) among Medicare beneficiaries aged ≥65 years in 43 US cities between 1992 and 2002. Temperature and dewpoint were obtained from ambient monitors in each city. We fit Poisson regression models to daily counts of admissions during summer months (May–September), with daily mean temperature as a linear term (for lag 0; lag 1; and the average of lags 2–5), controlling for day of the week; temporal trends, and dew point. Estimates were combined across the 43 cities, treating city as a random effect. Results: A 10°C increase in mean daily temperature at lag 0 was associated with an excess risk of hospitalization of 2.6% (95% CI: 1.3–4.0) for CVD, 4.1% (1.5–6.8) for MI, 6.3% (1.6–11.2) for diabetes, 4.4% (0.8–8.0) for COPD, and 4.0% (1.6–6.5) for pneumonia. No significant associations were observed at lag 1, whereas negative associations were observed for lags 2 to 5. For example, for CVD admissions, a 10°C increase in mean temperature at lags 2 to 5 was associated with a 9.4% (−10.5 to −8.3) deficit in risk and a net negative cumulative effect of heat exposure 5 days before the admission. Negative cumulative effects were found for all causes except diabetes. Conclusions: Although same-day heat was associated with excess risk of hospitalization, we did not find evidence of an enduring effect of heat in these preliminary analyses. These results are consistent with recent results from European cities. The lack of coherence between studies of heat-related mortality and morbidity deserves further exploration.