Citation

Ha J, Kim H, Hajat S. Environ. Health Perspect. 2011; 119(4): 542-546.

Affiliation

Korea Environment Institute.

Copyright

(Copyright © 2011, National Institute of Environmental Health Sciences)

DOI

10.1289/ehp.1002080

PMID

21233056

PMCID

PMC3080938

Abstract

BACKGROUND: It has recently been postulated that low-mortality levels in the previous winter may increase the proportion of vulnerable individuals in the pool of people at risk of heat-related death during the summer months. OBJECTIVES: We explored the sensitivity of heat-related mortality in summer (June-August) to mortality in the previous winter (December-February) in Seoul, Daegu, and Incheon in South Korea, from 1992-2007, excluding 1994. METHODS: Poisson regression models adapted for time-series data were used to estimate associations between a 1°C increase in average summer temperature (on the same day and the previous day) above city-, age-, and cause of death-specific thresholds and daily mortality counts. Effects were estimated separately for summers preceded by winters of low- and high-mortality, with adjustment for secular trends. RESULTS: Temperatures above city-specific thresholds were associated with increased mortality in all 3 cities. Associations were stronger in summers preceded by winters with low versus high mortality levels for all non-accidental deaths and, to a lesser extent, among those aged 65 years or older. Effect modification by previous winter mortality was not evident when deaths were restricted to cardiovascular disease (CVD) outcomes in Seoul. CONCLUSIONS: Our results suggest that low winter all-cause mortality leads to higher mortality in the following summer. Evidence of a relation between increased summer heat-related mortality and previous wintertime deaths has the potential to inform public health efforts to mitigate effects of hot weather.

Language: en