Background Around 20,000 extra deaths occur in winter in the UK every year. Cardiovascular disease (CVD) is one of the main causes. We aimed to assess firstly the overall effect of a cold weather spell on risk of CVD, and secondly the possible modifying influences of socio-demographic, clinical, health behaviour and environmental factors on people’s susceptibility to CVD events.
Methods Data were used from the British Regional Heart Study, a prospective study in British men. 4,252 men from general practices in 24 towns across Great Britain were followed from 1998–2000, when aged 60–79 years, until 2012 for CVD incidence. Using daily temperature for participants’ town of residence, cold spells were defined as four consecutive days when temperature fell below the 10th percentile specific to the local weather station for that calendar month. These were identified for dates immediately prior to an event and for equivalent days of the week within the same month. A case-crossover analysis was carried out.
Results 915 men suffered a CVD event during follow-up: of these 514 suffered fatal events either at the time of the first CVD event or later during follow-up. The odds ratio associated with a cold spell for all CVD events was 2.05 (95% CI 1.39–3.04, p < 0.001), and 1.79 (95% CI 1.04–3.09, p = 0.035) for fatal events. There was no significant evidence for effect modification by age group, prevalent CVD, diabetes, occupational social class, region of residence, physical activity, being retired, living alone, or being married. There were suggestions that men who consumed alcohol more than occasionally had a greater odds than other men (OR 3.03 vs 1.50, p = 0.088), that current smokers had a greater odds than non-smokers (4.51 vs 1.69, p = 0.073), and that men with COPD had a greater odds (4.05 vs 1.70, p = 0.088). Men who owned a car and also a house that was both centrally heated and double glazed had a lower odds than others (1.43 vs 2.75, p = 0.12).
Discussion Spells of cold days, occurring commonly in winter, double the risk of CVD events. Men who either drink or smoke, or suffer COPD, may carry increased susceptibility to CVD in winter, over and above their usual increased risk. There was weak evidence for a protective effect for well-heated homes. The absence of clear relative increases in susceptibility still means that people with generally high absolute risk of CVD will carry the highest absolute increase in risk during cold periods.
- weather cardiovascular susceptibility