Absolute and physiological humidity metrics and cardiovascular disease risk in aging: a nationwide study from China

Background climate change increases cardiovascular risks from humidity, but effects of specific metrics-including relative humidity (RH), mixing ratio (MR), specific humidity (SH), absolute vapor pressure (AVP), vapor pressure deficit (VPD), and dew point temperature (DPT)-on aging are unclear. Methods we analyzed China Health and Aging Longitudinal Study data (CHARLS, 2011-2015; n=25,614, ≥45y) with high-resolution humidity measurements. Multivariate logistic regression and weighted quantile sum (WQS) models assessed associations between these six humidity indicators and heart disease, adjusted for confounders. Results MR showed the strongest association with heart disease (aOR=2.05, 95%CI:1.89-2.22 per IQR), followed by SH (aOR=2.04) and VPD (aOR=1.57). WQS identified VPD as most influential (45% weight), but MR correlated perfectly with SH (r=1), supporting its use as a primary indicator. RH, AVP and DPT showed weaker associations. Conclusion: MR and VPD are key humidity-related predictors of heart disease in middle-aged and older adults. Early-warning systems and targeted interventions should focus on MR, with VPD as a complementary metric, especially in vulnerable populations.