Cold spells and the risk of hospitalization for asthma: New York, USA 1991-2006.

ABSTRACT

PURPOSE: A study was conducted to investigate whether prolonged periods of very cold temperatures were associated with an increased risk of hospitalization for asthma. METHODS: Hospitalization admissions with a principal diagnosis of asthma were identified in New York State, USA, for the months November through April from 1991 to 2006. A cold spell was defined as three or more consecutive days where the daily mean of universal apparent temperature (UAT) within a week prior to admission was at the 10th percentile or less. The percentage change in asthma hospitalizations during and after a cold spell was compared to the average daily number of hospitalizations preceding the cold spell using time series analysis. RESULTS: The average temperature during winter cold spells (December through March) was -15 °C, compared to -6 and -2 °C for cold spells in November and April, respectively. Cold spells during the winter months were associated with a mean decline of 4.9 % in asthma admissions statewide (95 % CI -7.8, -1.9 %). After a cold spell, no statistically significant changes were apparent during the winter months, but asthma hospitalizations increased after cold spells in the transitional months of November (mean = 9.6, 95 % CI 5.5, 13.9 %) and April (mean = 5.0, 95 % CI 1.2, 9.0 %). CONCLUSIONS: The results suggest that during prolonged periods of severe cold asthmatics may adhere to medical guidelines and limit their exposure, thereby preventing exacerbations. They may be less likely to alter their behavior in the more moderate months of November and April.