Three systems keep you near 37°C, and all three fade with age. Sweat glands fire less ¹. Skin blood flow that should dump or hold heat rises only about a third as much as at twenty ². And the thirst signal is the first to break: deprived of water, older adults end up measurably more dehydrated than younger ones yet feel less thirsty and drink less when finally allowed ³. You feel fine while you're not.

The body count is larger than almost anyone realises. The 2003 death rate climbed steadily with age, and the summer of 2022 added another 61,672 heat deaths across Europe ⁴. Most of them aren't textbook heatstroke; they're heart attacks, strokes, and heart-failure crashes in people whose cardiovascular reserve gives out under heat strain ⁵⁶. Air conditioning moves the number: across 1970s heatwaves, nursing homes without it had more than twice the death rate of those with it ⁷. Cold runs in reverse — each degree below about 18°C raises elderly mortality, mostly through heart and lung events rather than hypothermia ⁸.

Set it up in spring, before the heatwave arrives.

Within a week of the cool bedroom and the drinking schedule, you wake fewer times and the 4 p.m. wrung-out feeling you'd blamed on age turns out to be the heat ¹⁰. Through the first real heatwave, the cardiologist finds nothing new on the August trace and the summer ends without a story. Across years, each summer you stay out of the hospital tail is a year your heart and your independence hold. On the European averages, the older adult who took the protocol is likelier to still be in their own kitchen at seventy-eight ⁴.