Abstract 11723: Seasonal Variation in Cardiac Death Rates is Uniform across Different Climates
BACKGROUND Total and cardiac death rates are increased in winter versus summer. The factors influencing this seasonal variation are not well studied.
METHODS We obtained daily death certificate data from health departments in a variety of climates (Texas [TX], Arizona [AZ], Georgia [GA], Los Angeles [LA], Washington [WA], Pennsylvania [PA], Massachusetts [MA]) from 1/1/05 through 12/31/08 and compared them. Average seasonal values for each day of the year were obtained by calculating a 19-day centered moving average (to smooth the curve) and taking the average values of the 4 years’ curves.
RESULTS Average seasonal values varied by location but all locations revealed a “U” shaped curve with peaks in winter and troughs in summer (Figure 1). Using raw daily death rates, the peak 8 day period was significantly greater than the trough 8 day period (p<0.0001 for each location). Total death rates parallel circulatory death rates. The data were normalized to (divided by) the average annual death rate for that location (Figure 2) revealing very similar patterns in the difference between peak versus trough despite very different climates. The maximum % change (using the peak 8 day period and the trough 8 day period) was calculated using raw daily death rates. Maximum % change was similar, 26-36% across a wide spectrum of climates (p = NS between locations) (Figure 2).
CONCLUSIONS While different locations report different average total and circulatory death rates, when normalized by average annual death rate the “U” curves are superimposed suggesting an acclimatization phenomenon. There is a 26-36% greater death rate in winter than summer despite different locations and climates.
- © 2012 by American Heart Association, Inc.