Urban heat exposure and health-related quality of life across contrasting districts with spatial vulnerability assessment

Urban populations in hot, arid cities face accelerating physiological and psychological burdens from prolonged outdoor heat exposure, yet quantitative assessments linking thermal stress indices to health-related quality of life (HRQoL) in Middle Eastern megacities remain scarce. A cross-sectional survey encompassed 502 adults across 6 Baghdad districts between June 2021 and August 2023, integrating Universal Thermal Climate Index (UTCI) measurements with Short Form-36 Health Survey (SF-36). Three automatic weather stations recorded meteorological variables, including air temperature, relative humidity, wind speed, and mean radiant temperature, and Landsat-8 and Sentinel-3 imagery yielded land surface temperature data. Structured interviews recorded daily outdoor heat exposure duration and occupational category. Physical Component Summary (PCS) scores declined from 62.1 in participants with low heat exposure to 36.2 in participants with extreme exposure, while Mental Component Summary (MCS) scores fell from 58.4 to 33.8 over the same range. Multivariable linear regression identified UTCI as the dominant independent predictor of PCS (standardised β = −0.42, p < 0.001) and MCS (β = −0.38, p < 0.001) after adjustment for age, sex, occupational category, and a spatially derived heat vulnerability index (HVI). Outdoor construction workers and elderly residents carried disproportionate HRQoL deficits, with construction workers recording the lowest PCS (38.1) of any occupational subgroup. A spatially resolved HVI identified Al-Dora and Al-Sadr City as districts combining the highest thermal loads with the lowest adaptive capacity.