Short-term effects of air temperature on mortality and effect modification by air pollution in three cities of Bavaria, Germany: a time-series analysis.
BACKGROUND
Air temperature has been shown to be associated with mortality; however, only very few studies have been conducted in Germany. This study examined the association between daily air temperature and cause-specific mortality in Bavaria, Southern Germany. Moreover, we investigated effect modification by age and ambient air pollution.


METHODS
We obtained data from Munich, Nuremberg as well as Augsburg, Germany, for the period 1990 to 2006. Data included daily cause-specific death counts, mean daily meteorology and air pollution concentrations (particulate matter with a diameter<10 μm [PM10] and maximum 8-h ozone). We used Poisson regression models combined with distributed lag non-linear models adjusting for long-term trend, calendar effects, and meteorological factors. Air pollutant concentrations were categorized into three levels, and an interaction term was included to quantify potential effect modification of the air temperature effects.


RESULTS
The temperature-mortality relationships were non-linear for all cause-specific mortality categories showing U- or J-shaped curves. An increase from the 90th (20.0 °C) to the 99th percentile (24.8 °C) of 2-day average temperature led to an increase in non-accidental mortality by 11.4% (95% CI: 7.6%-15.3%), whereas a decrease from the 10th (-1.0 °C) to the 1st percentile (-7.5 °C) in the 15-day average temperature resulted in an increase of 6.2% (95% CI: 1.8%-10.8%). The very old were found to be most susceptible to heat effects. Results also suggested some effect modification by ozone, but not for PM10.


CONCLUSIONS
Results indicate that both very low and very high air temperature increase cause-specific mortality in Bavaria. Results also pointed to the importance of considering effect modification by age and ozone in assessing temperature effects on mortality.
Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Institute of Epidemiology II, Neuherberg, Germany. Electronic address: susanne.breitner@helmholtz-muenchen.de.
Susanne
S
Breitner
Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Institute of Epidemiology II, Neuherberg, Germany.
Kathrin
K
Wolf
United States Environmental Protection Agency, Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, RTP, NC, USA.
Robert B
RB
Devlin
United States Environmental Protection Agency, Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, RTP, NC, USA.
David
D
Diaz-Sanchez
Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Institute of Epidemiology II, Neuherberg, Germany.
Annette
A
Peters
Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Institute of Epidemiology II, Neuherberg, Germany.
Alexandra
A
Schneider
D000369:Aged, 80 and over; D000397:Air Pollution / Q000706:statistics & numerical data*; D002318:Cardiovascular Diseases / Q000401:mortality*; D002947:Cities / Q000706:statistics & numerical data*; D004784:Environmental Monitoring; D005260:Female; D005858:Germany; D006801:Humans; D008297:Male; D009026:Mortality / Q000639:trends*; D017711:Nonlinear Dynamics; D012140:Respiratory Tract Diseases / Q000401:mortality*
Age groups; Air pollution; Air temperature; Cause-specific mortality; Effect modification