Influenza epidemics and acute respiratory disease activity are associated with a surge in autopsy-confirmed coronary heart disease death: results from 8 years of autopsies in 34,892 subjects

Abstract

Aims: To determine whether influenza can trigger heart attacks, we investigated the impact of influenza epidemics on autopsy-proven coronary deaths.

Methods and results: We studied weekly death due to acute myocardial infarction (AMI) and chronic ischaemic heart disease (IHD) in autopsies conducted in 1993 to 2000 in St Petersburg, Russia. We plotted the weekly acute respiratory disease (ARD) counts and influenza epidemics against AMI and chronic IHD deaths. There were 11,892 subjects dying of AMI and 23 000 subjects dying of chronic IHD. Median age was 75 for women and 65 for men. In every year, a peak of AMI and chronic IHD deaths were present and coincided with the influenza epidemic and peak ARD activity. A similar pattern was seen for each subgroup of men, women, subjects 50 years or older, and subjects 70 years or older. When comparing the average influenza epidemic weeks to average off-season weeks, the odds for AMI and chronic IHD death increased by 1.30 (95% confidence interval (CI): 1.08-1.56) and 1.10 (95% CI: 0.97-1.26), respectively.

Conclusion: Influenza epidemics are associated with a rise in autopsy-confirmed coronary deaths. Influenza vaccination should be advocated for patients at high risk of developing cardiovascular events.

Figure 1

Smoothed data plot of deaths due to acute myocardial infarction and morbidity from acute respiratory disease from 1993 to 2000 in the whole study population. The continuous line depicts acute myocardial infarction mortality and the dashed line indicates acute respiratory disease morbidity and grey columns indicate influenza epidemic periods. The thick black ladders at the bottom of each year's plot indicate the four calendar quarters of Q1, Q2, Q3, and Q4.

Figure 2

Smoothed data plots of deaths due to acute myocardial infarction and morbidity from acute respiratory disease from 1993 to 2000 in subjects aged 50 or older (A), and aged 70 or older (B), in men (C) and women (D). The continuous line depicts acute myocardial infarction mortality and the dashed line indicates acute respiratory disease morbidity and grey columns indicate influenza epidemic periods. The thick black ladders at the bottom of each year's plot indicate the four seasons in the order of calendar quarters Q1, Q2, Q3, and Q4.

Figure 3

Time series cross-correlation of acute respiratory disease morbidity and acute myocardial infarction mortality. Peak correlations are near time zero, within an approximately 2 week peak window on either side, and a decline of about 10 weeks duration.

Figure 4

Time series decomposition forecast of total seasonal acute myocardial infarction mortality shows that a seasonal periodicity is predictable from trend, season, and underlying cycle. The period beyond the dots shows forecasted future seasonal mortality 1 year beyond the actual data. The predictions are for winter (W), spring (SP), summer (SU), and fall (F) projecting into the hypothetical year 10.