The relationship between influenza outbreaks and acute ischemic heart disease in Maryland residents over a 7-year period.
BACKGROUND
We sought to expand the understanding of relationships of influenza outbreaks to ischemic heart disease (IHD)-related events.


METHODS
Retrospective data sources were used to examine relationships of intense influenza outbreak periods (intense-IOP) to rates of IHD-related hospitalizations and deaths for Maryland residents aged ≥ 50 years. Rate ratios (RRs) were calculated for medical outcomes during intense-IOP compared to non-IOP for 7 years.


RESULTS
RRs for IHD-related hospitalizations (RR=1.06), deaths (RR=1.16), and combined hospitalizations for IHD- and medically attended acute respiratory illness (MAARI) (RR=1.42) were significantly elevated during intense-IOP over the 7 years (P< .01). RRs for IHD-related hospitalizations increased significantly with age (P= .0007). Also, RRs for IHD-related hospitalizations each year were significantly correlated to proportions of circulating A/H3N2 viruses in that year (correlation coefficient [CC] =0.83, P= .02). Finally, for residents aged ≥ 65 years, RRs for IHD-related hospitalizations each year were significantly correlated with magnitude of the intense-IOPs in that year as measured by RRs for MAARI-related emergency department (ED) visits (CC=0.77, P= .04).


CONCLUSIONS
These data suggest that influenza infections, particularly by A/H3N2 viruses, are directly associated with acute IHD-related events in older individuals.
Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, USA.
Richard
R
Lichenstein
Laurence S
LS
Magder
Rita Elizabeth
RE
King
James Craig
JC
King
D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D008396:Maryland / Q000453:epidemiology; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D013997:Time Factors