Climatic influences on cardiovascular diseases

Table 3 Main studies on the relations between weather and hospital admissions

Ref.	Population and setting	Year	Main results
Ebi et al[59]	Three Californian regions, United States	1983-1998	Association between temperature and hospitalizations varied by region, age, and gender
Michelozzi et al[41]	Twelve European cities participating in the Assessment and Prevention of Acute Health Effects of Weather Conditions in Europe (PHEWE) project	1990-2001	For an 18°C increase in maximum apparent temperature above a threshold, respiratory admissions increased by 14.5% (95%CI: 1.9–7.3) and 13.1% (95%CI: 0.8–5.5) in Mediterranean and North-Continental cities, respectively. In contrast, the association between temperature and cardiovascular and cerebrovascular admissions tended to be negative and did not reach statistical significance
Vaneckova and Bambrick[52]	Sidney, Australia	1991-2009	On hot days, hospital admissions increased for all major categories. This increase was not shared homogeneously across all diseases. Admissions due to some major categories increased one to three days after a hot day (e.g., respiratory and cardiovascular diseases) and on two and three consecutive days
Goldie et al[54]	Darwin, Australia	1993-2011	Nighttime humidity was the most statistically significant predictor (P < 0.001), followed by daytime temperature (P < 0.05). Hot days appeared to have higher admission rates when they were preceded by high nighttime humidity
Linares and Diaz[28]	Daily emergency admissions between May and September in the Hospital General Universitario Gregorio Maranòn, Madrid, Spain	1995-2000	The temperature above which hospital admissions soar coincides with the temperature limit above which mortality sharply rises, which, in turn, coincides with 95th percentile of the maximum daily temperature series
Chan et al[53]	Hong Kong, China	1998-2009	During summer, admissions increased by 4.5% for every increase of 1°C above 29°C; during winter, admissions increased by 1.4% for every decrease of 1°C within the 8.2–26.9 °C range. Admissions for respiratory and infectious diseases increased during extreme heat and cold, but cardiovascular disease admissions increased only during cold temperatures. During winter, for every decrease of 1°C within the 8.2–26.9 °C range, admissions for cardiovascular diseases rose by 2.1%
Yitshak-Sade et al[61]	Respiratory, cardiac and stroke admissions of adults ≥ 65 (2015660), New England, United States	2001-2011	The short-term temperature effect was higher in months of higher temperature variability as well. For cardiac admissions, the PM2.5 effect was larger on colder days (0.56% versus −0.30%) and in months of higher temperature variability (0.99% vs −0.56%)
van Loenhout et al[55]	the Netherlands	2002-2007	Positive relationship between increasing temperatures above 21 °C and the risk for urgent emergency room admissions for respiratory diseases. For admissions for circulatory diseases, there is only a small significant increase of risk within the 85+ age group for moderate heat, but not for extreme heat
Ponjoan et al[58]	Catalonia, Spain	2006-2016	The overall incidence of cardiovascular hospitalizations significantly increased during cold spells (RR = 1.120; 95%CI: 1.10–1.30) and the effect was even stronger in the 7 d after the cold spell (RR = 1.29; 95%CI: 1.22–1.36). Conversely, cardiovascular hospitalizations did not increase during heatwaves
Shiue et al[60]	Ten percent of daily hospital admissions across Germany	2009-2011	Admissions due to diseases of pericardium, nonrheumatic mitral and aortic valve disorders, cardiomyopathy, atrioventricular block, other conduction disorders, atrial fibrillation and flutter, and other cardiac arrhythmias peaked when physiologically equivalent temperature was between 0 and 10°C
Tian et al[57]	184 cities in China	2014-2017	a 1˚C increase in short-term temperature variability (calculated from the SD of daily minimum and maximum temperatures) at 0–1 days was associated with a 0.44% (0.32%–0.55%), 0.31% (0.20%–0.43%), 0.48% (0.01%–0.96%), 0.34% (0.01%–0.67%), and 0.82% (0.59%–1.05%) increase in hospital admissions for cardiovascular disease, ischemic heart disease, heart failure, heart rhythm disturbances, and ischemic stroke, respectively

CHD: Coronary heart disease; CVD: Cardiovascular diseases; CI: Confidence interval; PM: Particulate matter; RR: Relative risk; SD: Standard deviation.