Climatic influences on cardiovascular diseases

Table 2 Main studies on the relations between weather and cardiovascular mortality

Ref.	Population and setting	Year	Main results
Gyllerup et al[44]	Men aged 40–64 from 259 municipalities in Sweden	1975-1984	Coronary mortality is more strongly associated with cold climate than with other explanatory factors such as cholesterol, socioeconomic factors, or tobacco
Crawford et al[43]	Deaths in Northern Ireland, United Kingdom	1979-1998	Low temperature is associated with highest mortality rates from myocardial infarction
Gerber et al[45]	Olmsted County, Minnesota, United States	1979-2002	RR of sudden death, but not of myocardial infarction, was increased in low temperatures (1.20, 95%CI: 1.07-1.35, for temperatures below 0°C vs 18°C-30°C). These associations were stronger for unexpected sudden death (P < 0.05)
Wichmann et al[49]	Gothenburg, Sweden	1985-2010	No evidence of association between temperature and CHD deaths in the entire year, warm or cold periods
Enquselassie et al[3]	Australian community-based register of heart disease (the WHO MONICA Project)	1992	Coronary deaths were more likely to occur on days of low temperature (and to a much lesser extent, of high temperature. Patterns of sudden and non-sudden deaths were not associated with weather conditions. Both longer-term seasonal effects and daily temperature effects exist
Dilaveris et al[48]	AMI deaths in Athens, Greece	2001	The best predictor was the average temperature of the previous 7 d; the relation between daily myocardial infarction deaths and 7-d average temperature (R2 0.109, P < 0.001) was U-shaped
Zhang et al[35]	District of Wuhan, China	2003-2010	For cold effects over lag 0–21 d, a 1°C decrease in mean temperature below the cold thresholds was associated with a 3.65% (95%CI: 2.62, 4.69) increase in cardiovascular mortality and 21.57% (95%CI: 12.59, 31.26) increase in CHD mortality. For hot effects over lag 0–7 d, a 1°C increase in mean temperature above the hot thresholds was associated with a 34.10% (95%CI: 25.63, 43.16) increase in cardiovascular mortality and 17.00% (95%CI: 7.91, 26.87) increase in CHD mortality
Wang X et al[47]	Beijing and Shanghai, China	2007–2009	The cold effects on cause-specific cardiovascular mortality reached the strongest at lag 0–27, while the hot effects reached the strongest at lag 0–14
Yang J et al[6]	Nine Chinese mega-cities	2007–2013	Statistically significant nonlinear associations between temperature and mortality were observed, with a total of 50658 deaths from myocardial infarction attributable to non-optimal temperatures
Yin Q, Wang J[50]	Beijing, China	2010-2012	When extremely high temperatures occur continuously, at varying temperature thresholds and durations, adverse effects on CVD mortality vary significantly. The longer the heat wave lasts, the greater the mortality risk is. When the daily maximum temperature exceeded 35 °C from the fourth day onward, the RR attributed to consecutive days’ high temperature exposure saw an increase to about 10% (P < 0.05), and at the 5th day, the RR reached 51%

AMI: Acute myocardial infarction; CHD: Coronary heart disease; CVD: Cardiovascular diseases; CI: Confidence Interval; OR: Odds ratio; RR: Relative risk.