The Subclinical Cardiovascular Effects of Nonoptimum Ambient Temperature: A Longitudinal Study in 15 Chinese Cities

Short-term ambient temperature is linked to cardiovascular morbidity and mortality, but subclinical responses remain unclear. Using repeated health examinations from 247,641 adults in 15 Chinese cities (2013–2020), we assessed 20 cardiovascular indicators with linear mixed-effects and distributed lag nonlinear models. The indicator-specific sample sizes ranged from 1119 to 219,090 participants. Exposure–response relationships were near-linear or inversely J-shaped for ten indicators, U-shaped or inverted U-shaped for seven, and atypical or unclear for three. Low temperature was associated with 18 indicators, peaking at lags 0–5 days, whereas high temperature was associated with seven, peaking at lags 0–6 days. Relative to the reference temperatures, extremely low-temperature exposure (P1, −9 °C) was associated with cumulative increases over lag days 0–10 of 6.52%–13.99% in blood pressure, 4.63%–46.23% in inflammatory markers, 5.11%–10.48% in cardiac-associated enzymes, and 6.29% in homocysteine, as well as cumulative changes ranging from −2.68% to 5.36% in hemorheological parameters and from −4.96% to 12.05% in lipid-related indicators. Extremely high-temperature exposure (P99, 32 °C) was associated with cumulative changes ranging from −1.47% to 4.84% in hemorheological parameters and increases of 1.62%–1.91% in lipid indicators and 1.32%–15.13% in cardiac-associated enzymes. These findings provide multicenter evidence that nonoptimum temperature is associated with early cardiovascular alterations.