Did summer weather factors affect gastrointestinal infection hospitalizations in New York State?

Gastrointestinal infections, a substantial public health problem worldwide, have been associated with single weather factors but the joint effect of multiple weather factors on gastrointestinal infections remains unclear.

We conducted a retrospective time-series analysis to investigate effects of weather conditions on hospitalizations for gastrointestinal infections (GIH) in New York State in July and August from 1991 to 2004. Applying generalized additive model (GAM), we evaluated the associations between daily GIH count and multiple weather factors including temperature, humidity, and precipitation (0-10 lag days), adjusting for long term trend, seasonality, and calendar effects.

Maximum temperature, minimum temperature, and maximum universal apparent temperature (UAT) showed that each °C increase in temperature was significantly associated with an increase (0.70-0.96%) in daily GIH count, with the greatest impacts observed at lag 1. Extreme heat (EH: >90th percentile) (3.68% at lag 1) and precipitation (0.31% at lag 4) showed larger impacts on increases of GIH and a clear dose-response relationship for EH. Stratified analyses showed that the impacts of extreme heat on GIH tend to be greater among Hispanics, blacks, females, and those with bacterial infections.

We found that high maximum and minimum temperature, UAT, precipitation, and extreme heat in summer significantly increased the risks of GIH in NYS. Our findings also suggest that bacteria might be a significant cause for GIH in the summer, and minority, female and those with bacterial infection may be more vulnerable to heat's effects on GIH.