Around 2,700 people are estimated to have died from heat-related causes during the May and June 2026 heatwaves in England and Wales, making this one of the deadliest heat periods since heat mortality monitoring began in 2004. But according to Michael Anderson, editor of the Institute and Faculty of Actuaries' (IFoA) Longevity Bulletin, one summer is unlikely to change the assumptions life insurers use to model future mortality.
"It's a little bit too soon to get a firm conclusion," Anderson told Insurance Business UK. "In the past, where you've had heatwaves where there have been more deaths than we were expecting, usually for a few weeks after that you then have fewer deaths than you were expecting. So it generally has tended to affect timing rather than the total number of deaths across the whole piece."
The estimate comes from a rapid attribution analysis by the London School of Hygiene & Tropical Medicine, Imperial College London and the Met Office. It contrasts with recent findings from the Continuous Mortality Investigation (CMI), which reported the lowest first-half mortality on record for UK men and women in 2026, largely because of a mild flu season.
Anderson said the wider context matters.
"Mortality in 2026 has been very, very low so far, mainly because we had a very low level of deaths in the winter," he said. "So a blip going the other way, we could still end up being in a year where there's low mortality overall."
Anderson said insured populations have historically experienced a smaller proportional impact from heatwaves than the wider public.
"An insured population usually would have less of an increase in the event, for a variety of factors – not least of which is that the underlying population is usually more affluent than the general population, and a more affluent population, because of health and lifestyle factors, typically tends to be more healthy to start with," he said.
"There's other socio-economic factors that would lead to that population being more protected, in a sense, from some of those negative effects."
He stressed this reflected population averages rather than individual cases, but said it helps explain why insurers may not experience the same mortality pattern seen in national statistics. He added that insurers' own experience can also take longer to emerge than the weekly mortality data published by the Office for National Statistics (ONS).
"That 2,700 is a big number for sure, but just to put it in total context, in England and Wales last year there were around about 570,000 deaths across the whole calendar year, so it's a little bit under half a per cent. So it's enough to be noticeable, but it's also at that edge of where, if you're doing modelling, it's difficult to place a lot of weight on it."
Anderson drew a distinction between the assumptions insurers use to hold capital and those used to price and reserve for future mortality.
Under Solvency UK, insurers already hold capital against extreme mortality events. If heatwaves become materially more frequent or severe, those assumptions could eventually change. Altering the central "best estimate" mortality assumption, however, would require much stronger evidence.
"That's probably quite a strong threshold for people to want to start baking that in," he said. "They would want to see that for a number of years."
The bigger question, Anderson said, is whether repeated heatwaves create genuinely higher mortality or simply shift deaths that would previously have occurred during winter.
"Does that start to shift where you have more of those excess deaths in the summer? And is it just a moving of things around and the overall levels are still the same, or is it actually starting to affect the overall levels as well?" he said.
He also pointed to adaptation measures, including greater use of cooling technologies and better protection for vulnerable people, as factors that could influence future mortality, even as climate scientists expect heatwaves to become more frequent.
"What the meteorologists and climate scientists are all saying is the most likely outcome, unfortunately, on the path that we're on at the moment."
For now, Anderson believes insurers are looking for evidence of a sustained trend rather than a single exceptional summer. If repeated heatwaves begin to increase overall mortality rather than simply shift deaths between seasons, that is when life insurers are likely to revisit the assumptions they use to price and manage risk.
