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Cardiovascular Deaths and the Weather in Budapest
Toro, K., Bartholy, J., Pongracz, R., Kis, Z., Keller, E. and Dunay, G. 2010. Evaluation of meteorological factors on sudden cardiovascular death. Journal of Forensic and Legal Medicine 17: 236-242.

The authors write that "several studies have demonstrated that cardiovascular mortality has a seasonal distribution (Arntz et al., 2000; Weerasinghe et al. 2002; Nakaji et al., 2004; Kloner, 2006)," and that "the relationship between cold weather and ischemic heart disease mortality is well established (Vuori, 1987; Gyllerup et al., 1993; Gyllerup, 2000)," after which they state that "cold temperature may be an important factor in bringing on the onset of life-threatening cardiac events, even in regions with relatively mild winters," citing the study of Cagle and Hubbard (2005).

What was done
Working with data pertaining to 7450 cardiovascular-related deaths that occurred within Budapest, Hungary, between 1995 and 2004 -- where the deceased were "medico-legally autopsied" -- Toro et al. looked for potential relationships between daily maximum, minimum and mean temperature, air humidity, air pressure, wind speed, global radiation and daily numbers of the heart-related deaths.

What was learned
The six Hungarian scientists report and restate their primary finding numerous times throughout their paper, writing that (1) "both the maximum and the minimum daily temperatures tend to be lower when more death cases occur in a day," (2) "on the days with four or more death cases, the daily maximum and minimum temperatures tend to be lower than on days without any cardiovascular death events," (3) "the largest frequency of cardiovascular death cases was detected in cold and cooling weather conditions," (4) "we found a significant negative relationship between temperature and cardiovascular mortality," (5) "the analysis of 6-hour change of air pressure suggests that more acute or chronic vascular death cases occur during increasing air pressure conditions (implying cold weather fronts)," (6) "we found a high frequency of cardiovascular death in cold weather," (7) "a significant negative relationship was detected between daily maximum [and] minimum temperature[s] and the number of sudden cardiovascular death cases," and (8) "a significant negative correlation was detected between daily mean temperature and cardiovascular mortality."

What it means
In a summary statement pertaining to their work, Toro et al. write that "with these analyses, we confirmed the results of other studies (Donaldson et al., 1998; Gyllerup, 2000; Mercer, 2003) that mortality was in inverse relation to air temperature."

Arntz, H.R., Willich, S.N., Schreiber, C., Bruggemann, T., Stren, R. and Schultheis, H.P. 2000. Diurnal, weekly and seasonal variation of sudden death. Population-based analysis of 24,061 consecutive cases. European Heart Journal 21: 315-320.

Cagle, A. and Hubbard, R. 2005. Cold-related cardiac mortality in King County, Washington, USA 1980-2001. Annals of Human Biology 32: 525-537.

Donaldson, G.C., Tchernjavskii, V.E., Ermakov, S.P., Bucher, K. and Keatinge, W.R. 1998. Winter mortality and cold stress in Yekaterinburg, Russia: interview survey. British Medical Journal 316: 514-518.

Gyllerup, S. 2000. Cold climate and coronary mortality in Sweden. International Journal of Circumpolar Health 59: 160-163.

Gyllerup, S., Lanke, J., Lindholm, L.H. and Schersten, B. 1993. Cold climate is an important factor in explaining regional differences in coronary mortality even if serum cholesterol and other established risk factors are taken into account. Scottish Medical Journal 38: 169-172.

Kloner, R.A. 2006. Natural and unnatural triggers of myocardial infarction. Progress in Cardiovascular Diseases 48: 285-300.

Mercer, J.B. 2003. Cold -- an underrated risk factor for health. Environmental Research 92: 8-13.

Nakaji, S., Parodi, S., Fontana, V., Umeda, T., Suzuki, K., Sakamoto, I.J., Fukuda, S., Wada, S. and Sugawara, K. 2004. Seasonal changes in mortality rates from main causes of death in Japan (1970-1999). European Journal of Epidemiology 19: 905-913.

Vuori, I. 1987. The heart and the cold. Annals of Clinical Research 19: 156-162.

Weerasinghe, D.P., MacIntyre, C.R. and Rubin, G.L. 2002. Seasonality of coronary artery deaths in New South Wales, Australia. Heart 88: 30-34.

Reviewed 22 June 2011