Abstract P374: Monthly distribution of incident myocardial infarction in four United States communities: the Atherosclerosis Risk in Communities Study

Abstract

Background: A seasonal periodicity, winter peaks and summer troughs, of coronary heart disease (CHD) mortality has been identified by several investigations in various parts of the world using vital statistics. However, population-based studies describing seasonal patterns of validated incident non-fatal and fatal myocardial infarction (MI) are sparse. Thus, we aim to characterize the monthly distribution of acute MI incidence using data from the community surveillance component of the Atherosclerosis Risk in Communities (ARIC) Study. Methods: We estimated monthly rates of incident hospitalized acute MI from community-wide surveillance of 35 to 84 year old residents of the 4 ARIC Study communities (415,000 base population) from 2006 to 2010. Diagnostic classifications of all hospitalized MI events were independently validated using standardized algorithms applied to data on chest pain history, electrocardiographic evidence and cardiac biomarkers obtained from medical record abstraction. Age adjusted event rates (95% confidence intervals) per 10,000 persons stratified by ARIC community were calculated using population denominators estimated from United States census data. Analyses were weighted to account for the underlying sampling scheme. Results: From 2006 - 2010, a total of 8,578 estimated hospitalized MI events occurred, on the basis of 3,692 hospitalizations sampled. Of these, 71% [6,090 of 8,578] were in persons with no recorded history of MI. Overall, rates of incident MI varied across the months. Distributions of incident MI by month differed between ARIC communities, ranging from a monthly rate of 13.5/10,000 to 45.1/10,000 persons. In Forsyth, NC, we observed the highest monthly rates of incident MI in June [41.1 (23.0, 59.2)] and July [37.3 (26.5, 48.2)], and the lowest rates in September [26.2 (19.0, 33.5)] and March [27.8 (19.1, 36.4)]. Within Jackson, MS, event rates ranged from minimums of 27.1 (18.2, 35.9) and 28.2 (15.4, 40.9) in January and June to maximums of 45.1 (30.4, 59.8) and 39.9 (27.2, 52.7) in May and August. In Minneapolis, MN, the highest monthly rates of incident MI occurred in June [30.0 (19.8, 40.2)] and December [25.3 (12.6, 38.0)], and the lowest rates in October [13.5 (8.4, 18.6)] and September [15.5 (10.5, 20.5)]. Within Washington County, MD, rates of incident MI peaked in April [29.2 (18.3, 40.1)] and November [27.2 (15.8, 38.6)], and reached lows in August [14.7 (9.9, 19.4)] and January [17.0 (11.3, 22.8)]. Conclusions: From 2006 - 2010, monthly distributions of incident MI rates differed between ARIC communities. Across the climatologically diverse ARIC sites, we did not observe seasonal patterns of MI incidence typically reported of CHD mortality (i.e. winter peaks and summer troughs). Triggers for incident MI events are complex and these data suggest they may involve factors not predominately tied to seasonal transitions in these communities.