[Heat and burden of diseases: impacts and future projections in capitals of the Legal Amazon.]

Under the influence of climate change, environmental exposure to heat and pollution grows, exacerbated by extreme events, increasing the risk of mortality in vulnerable areas. We aimed to evaluate the present (2000-2019) and future effects of heat on the burden of cardiovascular (in people aged 45 years or older), respiratory (in people aged 60 years or older) and all-cause (in people aged 1 year or more) diseases in capitals of the Legal Amazon (Brazil).

An ecological study was conducted to initially estimate, for the period 2000-2019, the relative risk (RR) of exposure-response related to the effects of temperature on years of life potentially lost (YLL) using the generalized linear regression model (GLM), combined with the distributed non-linear lag model (DLNM); and the fractions of YLL attributable to heat from the prospective perspective (forward). Subsequently, the results were estimated in the baseline period (1970-2005) and projected into the future in the specific levels of warming and periods: 1.5 ºC (2010-2039), 2 ºC (2040-2069) and 4 ºC (2070-2099), considering the temperature data from the WCRP CORDEX regional climate model in RCP8.5 scenario.

The RR of YLL increased significantly in the capitals due to exposure to heat and marked thermal amplitudes between 2000-2019, with the major effects on respiratory diseases in Río Blanco (14%), due to all causes in Manaus (12%) and cardiovascular in Cuiabá (9%). Compared with the baseline period, the period 2040-2069 showed the largest increase (10.40 times) in the fraction of the number of YLL attributable to heat in the region, with the predominance of cardiovascular diseases. The findings were not completely conclusive, the low precision of the estimated confidence intervals did not show the significance of the negative effect of heat.

Regardless of its significance, heat increases the risk of years of life lost in the short and medium term. The results support the need to include climate change mitigation and adaptation measures as public health protection policies.