Hot summer nights could lead to more cardiovascular deaths in some older men, according to new Canadian research.
A University of Toronto study, published today by *BMJ Open*, analysed a possible link between high temperatures at night and increased CVD among people aged 60 to 69 by studying data from the Office for National Statistics on adult deaths attributed to CVD for June and July between 2001 and 2015 in England and Wales.
They also gathered corresponding information from official USA data for King County, Washington, which is at parallel latitude to England and Wales and has comparable land-ocean atmospheric properties, as well as similarly low prevalence of residential air conditioning. The US data, however, only included men.
The team also examined official meteorological data from the UK and the USA.
They found in England and Wales there were 39,912 CVD deaths (68.9% men) recorded in England and Wales between 2001 and 2015 and 488 deaths in King County.
A 1°C rise in the usual summer night-time temperature in England and Wales was associated with a 3.1% increase in the risk of CVD mortality among men aged 60–64, but not older men or either women age groups.
In King County, a 1°C rise was associated with a 4.8% increased risk of CVD mortality among those aged 65 and under, but not in older men.
The team also found that CVD rates overall declined substantially in both regions annually and notably over the summer months, in line with greater population uptake of effective primary and secondary preventive therapies over time.
However, a substantial residual risk persisted, with rates remaining more than 50% higher in adults aged 65–69 than in those aged 60–64 years in England and Wales.
While this is an observational study, and the researchers acknowledge some limitations to their work, they say the study included large population size data and used rigorous national mortality and meteorological data.
They write: “The present findings should stimulate similar investigation of exposure and event rates in other populous mid-latitude to high-latitude regions.
“Considering the growing likelihood of extreme summers in Western USA and UK, our results invite preventive population health initiatives and novel urban policies aimed at reducing future risk of CVD events.”
Majeed H, Floras JS. Warmer summer nocturnal surface air temperatures and cardiovascular disease death risk: a population-based study. *BMJ open* 29 March 2022. doi 10.1136/bmjopen-2021-056806
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