Abstract 17275: Temperature and Respiratory Infection Influence Seasonal Variation in Total and Ischemic Heart Disease Death Rates
BACKGROUND There is a clear seasonal pattern in total and cardiac deaths, with peaks in winter. Factors influencing this seasonal variation remain unclear. Our purpose was to determine to what extent temperature and influenza play a role.
METHODS Using Poisson time series models, we examined the association between weekly mortality (all-cause and ischemic heart disease (IHD] related) and apparent temperature (temp) (human-perceived temperature calculated from temperature and humidity) for Texas (TX) and Los Angeles County (LA) from 1/1/05 through 12/31/08. Effect modification of this association by weekly influenza-like illness (ILI) was explored (defined as fever and cough / sore throat). ILI is expressed as the % of total patient visits due to ILI as reported by participating health care providers (urgent care clinics, ERs, etc.).
RESULTS We found that temp correlated significantly with total and IHD deaths in both TX and LA (p<0.01 in all models except IHD in LA). However, the relationship between temp and deaths differed. In both locations total and IHD deaths increased during extreme cold. In LA, but not in TX, total and IHD deaths also increased during extreme heat. After adjustment for these temperature effects, we found that ILI correlated significantly with total and IHD deaths in both TX and LA (p<0.01 in all models). The Figure shows the very similar annual and intermediate peaks (stars) in both IHD deaths and ILI in TX. An increase in ILI resulted in increased mortality with a larger effect for IHD deaths than total deaths (20% and 19% higher for TX and LA, respectively).
CONCLUSIONS These data indicate that people living in different climates respond differently to changes in apparent temperature. TX has hotter summers than LA, but deaths did not increase in TX during extreme heat suggesting an acclimation phenomenon. Respiratory infection is significantly associated with total and especially IHD deaths throughout the year and especially during annual peaks.
- © 2012 by American Heart Association, Inc.