Several lines of evidence point to a possible decrease in population sensitivity to heat, albeit mainly for high-income countries , arising from the implementation of heat warning systems, increased awareness and improved quality of life. . Evidence suggests a general decrease in the impact of heat on daily mortality , a decline in the relative risk attributable to heat  and an increase in the minimum mortality temperature  . It is difficult to draw conclusions regarding trends in heat sensitivity for low- to middle-income countries and specific vulnerable groups as these are under-represented in the literature . Trends in heat sensitivity are generally believed to be scale and situation dependent, but there is considerable variability in changes in heat sensitivity as measured by trends in heat-related mortality or MMT , with notable variability across different population groups .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report