Seasonality and coronary heart disease deaths in United States firefighters.
United States firefighters have a high on-duty fatality rate, and coronary heart disease is the leading cause. Seasonality affects the incidence of cardiovascular events in the general population, but its effects on firefighters are unknown. This study statistically examined the seasonal and annual variation of all on-duty coronary heart disease deaths among US firefighters between 1994 and 2004 using the chi-square distribution and Poisson regression model of the monthly fatality counts. It also examined the effect of ambient temperature (apparent as well as wind chill temperature) on coronary heart disease fatalities during the study span using a time-stratified, case-crossover study design. When grouped by season, we observed the distribution of the 449 coronary heart disease fatalities to show a relative peak in winter (32%) and relative nadir in spring (21%). This pattern was significantly different (p=0.005) from the expected distribution under the null hypothesis of season having no effect. The pattern persisted in additional analyses, stratifying the deaths by the type of duty in which the firefighters were engaged at the time of their deaths. In the Poisson regression model of the monthly fatality counts, the overall goodness-of-fit between the actual and predicted case counts was excellent (chi(4)(2)=16.63; p=0.002). Two distinct peaks were detected: one in January-February and the other in August-September. Overall temperature was not associated with increased risk of on-duty death. After allowing for different effects of temperature in mild/hot versus cold periods, a 1 degrees C increase was not protective in cold weather; nor did it increase the risk of death in warmer weather. The findings of this study reveal statistical evidence for excess coronary heart disease deaths among firefighters during winter; however, the temporal pattern of coronary heart disease deaths was not linked to temperature variation. The seasonal pattern was also found to be independent of duty-related risks.
Mbanu
Ibeawuchi
I
Department of Environmental Health (Occupational Health Program), Harvard School of Public Health, Boston, MA, USA.
Wellenius
Gregory A
GA
Mittleman
Murray A
MA
Peeples
Lynne
L
Stallings
Leonard A
LA
Kales
Stefanos N
SN
D000328:Adult; D003327:Coronary Disease / Q000401:mortality*; D004630:Emergencies; D005260:Female; D005390:Fires; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000401:mortality*; D016012:Poisson Distribution; D012042:Registries; D012189:Retrospective Studies; D012621:Seasons; D013696:Temperature; D014481:United States / Q000453:epidemiology
Am J Epidemiol. 1993 Feb 1;137(3):331-41
8452141
Ann Hum Biol. 2005 Jul-Aug;32(4):525-37
16147400
J Occup Environ Med. 2006 Oct;48(10):1047-53
17033504
J Am Coll Cardiol. 1998 May;31(6):1226-33
9581712
Ann Emerg Med. 2002 Dec;40(6):625-32
12447340
Epidemiology. 2001 Mar;12(2):186-92
11246579
Chronobiol Int. 2006;23(6):1083-96
17190696
Int J Cardiol. 2004 Apr;94(2-3):229-33
15093986
Age Ageing. 1978 Nov;7(4):210-24
727071
Chronobiol Int. 2005;22(6):1121-35
16393712
Circulation. 2004 Dec 21;110(25):3781-8
15596560
Occup Med. 2001 Jan-Mar;16(1):101-8
11107227
N Engl J Med. 2007 Mar 22;356(12):1207-15
17377158
J Epidemiol Community Health. 1997 Dec;51(6):643-8
9519127
Am J Epidemiol. 1995 Jul 1;142(1):91-8
7785679
Circulation. 1999 Jul 6;100(1):E1-7
10393689
NFPA J. 1996 Jul-Aug;90(4):63-5, 68-70, 77
10158564
J Clin Pathol. 2006 Jan;59(1):64-6
16394282
Rev Esp Cardiol. 2004 Jan;57(1):12-9
14746713
Mayo Clin Proc. 1982 Nov;57(11):704-6
7132431
Int J Circumpolar Health. 2005 Dec;64(5):451-8
16440607
Environ Health. 2003 Nov 06;2(1):14
14613487
Int Arch Occup Environ Health. 1992;64(1):1-12
1399009