Seasonal Influenza Infections and Cardiovascular Mortality
What is the temporal association between population increases in seasonal influenza infections and mortality due to cardiovascular causes?
Time-series analysis of vital statistics records and emergency department visits in New York City, among cardiovascular deaths that occurred during influenza seasons between January 1, 2006, and December 31, 2012, were conducted. The 2009 novel influenza A(H1N1) pandemic period was excluded from temporal analyses. Emergency department visits for influenza-like illness, grouped by age (≥0 years and ≥65 years) and scaled by laboratory surveillance data for viral types and subtypes, in the previous 28 days were analyzed. The main outcome measures were mortality due to cardiovascular disease, ischemic heart disease, and myocardial infarction.
Among adults ages ≥65 years, who accounted for 83.0% (73,363 deaths) of nonpandemic cardiovascular mortality during influenza seasons, seasonal average influenza incidence was correlated year to year with excess cardiovascular mortality (Pearson correlation coefficients ≥0.75, p ≤ 0.05 for four different influenza indicators). In daily time-series analyses using four different influenza metrics, interquartile range increases in influenza incidence during the previous 21 days were associated with an increase between 2.3% (95% confidence interval [CI], 0.7%-3.9%) and 6.3% (95% CI, 3.7%-8.9%) for cardiovascular disease mortality, and between 2.4% (95% CI, 1.1%-3.6%) and 6.9% (95% CI, 4.0%-9.9%) for ischemic heart disease mortality among adults ages ≥65 years. The associations were most acute and strongest for myocardial infarction mortality, with each interquartile range increase in influenza incidence during the previous 14 days associated with mortality increases between 5.8% (95% CI, 2.5%-9.1%) and 13.1% (95% CI, 5.3%-20.9%). Out-of-sample prediction of cardiovascular mortality among adults ages ≥65 years during the 2009-2010 influenza season yielded average estimates with 94.0% accuracy using four different influenza metrics.
The authors concluded that emergency department visits for influenza-like illness were associated with and predictive of cardiovascular disease mortality.
This study reports that community-level rises in influenza-like illness were associated with and predictive of cardiovascular disease mortality. This association suggests that accurate and reliable forecasts of influenza activity may provide health professionals with additional weeks of lead time to plan and respond to seasonal increases in cardiovascular mortality. Furthermore, these data may help guide cardiovascular drug prescriptions for high-risk patients, planning and allocation of effective antiviral medications, and public health information campaigns.
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