Warmer nights may lead to more cardiovascular deaths in men

For every 1°C increase in summer nighttime temperatures, men's risk of death from cardiovascular disease increases by around 4%

Warmer-than-usual summer nights appear to lead to higher cardiovascular deaths in men in their early 60s, but not in women, according to a new study published in the online journal BMJ Open

Previous research has focused on the potential for warm summer weather, periods of extreme or prolonged heat that accompany a surge in deaths and hospitalizations from cardiovascular disease

However, findings related to age and sex have so far been inconsistent, so researchers at the University of Toronto in Canada set out to investigate any possible link between summer nighttime heat and increased cardiovascular disease (CVD) deaths among people aged 60 to 69.

They looked at data provided by the Office for National Statistics on adult deaths from cardiovascular disease in England and Wales in June and July each year between 2001 and 2015, because in those months , the UK has the most frequent and intense heatwaves

They also collected information from official U.

In addition, they looked at official weather data from the United Kingdom and the United States

The results showed that between 2001 and 2015, there were 39,912 cardiovascular deaths in England and Wales (68.

In England and Wales, every 1°C increase in summer nighttime temperature was associated with a 3.

In King County, a 1°C increase was associated with a 4.

Over the 15-year observation period, cardiovascular disease rates in both regions declined substantially each year in general, especially in summer, in line with more people receiving effective primary and secondary preventive treatment over time consistent

However, considerable residual risk remains, and the authors say that in England and Wales, adults aged 65-69 have more than 50% higher event rates than adults aged 60-64

This is concerning, they add, because in recent years, densely populated areas, such as those studied, have experienced a rise in the proportion of summer heat intensities at night rather than during the day

This is an observational study, so causation cannot be established, and the researchers also acknowledge some limitations of their work, such as the inability to obtain 15-year sex- and age-specific weekly results, and exposure data at the regional or city level, This may have identified a stronger association between summer nighttime heat and cardiovascular mortality in densely populated urban areas

However, one of the strengths of this study is its large population-scale data, and its rigorous use of national mortality and meteorological data

They concluded: "The current findings should inspire similar investigations of exposure and event rates in other densely populated mid- and high-latitude regions

"Given the increasing likelihood of extreme summers in the western US and UK, our findings suggest preventive population health initiatives and new urban policies aimed at reducing future cardiovascular disease risk