Beyond heatwaves and cold spells: Long-term exposure to short-duration extremes, behavioural pathways, and hypertension risk in a national Chinese cohort

BACKGROUND: Extreme temperature events (ETEs) are increasing in frequency, duration, and intensity under climate change. Evidence on whether long-term accumulated ETE exposure contributes to chronic cardiovascular disease remains limited, and behavioural pathways linking such exposure to cardiovascular risk are still insufficiently understood. METHODS: We demonstrated that commonly used identification strategies for estimating cumulative health impacts of long-term ETE exposure may yield biased estimates with limited interpretability when a complete set of temporally exclusive ETE categories within the exposure window is not jointly modelled. We therefore developed a new identification strategy emphasising that at least four conceptually related yet temporally exclusive ETEs - cold spells, short-duration cold extremes (SD-CEs), heatwaves, and short-duration heat extremes (SD-HEs) - should be examined simultaneously. Within this framework, we applied Cox models and four-way decomposition to examine long-term ETE exposure effects on hypertension and interactions with lifestyle behaviours, using national prospective cohort data (n = 8,147) from the China Health and Nutrition Survey. RESULTS: Higher SD-CE and SD-HE exposure was associated with increased hypertension risk (HR range: 1.05-1.06 and 1.04-1.05, respectively). SD-CEs additionally showed a significant non-linear association, with greater risk at higher exposure levels. Cold spells were associated with higher risk only under higher, more frequent cold thresholds, whereas heatwaves were not significantly associated with hypertension risk. ETE exposure primarily exerted its effects through direct pathways. Interactions with lifestyle behaviours were also evident: low physical activity attenuated hypertension risk, whereas short sleep duration and prolonged sedentary time amplified it. CONCLUSIONS: Short-duration extremes may be an overlooked but relevant dimension of temperature exposure for climate-sensitive hypertension prevention. While the associated risk is primarily driven by exposure-induced physiological load, interactions with lifestyle behaviours exert an additional influence. Our research also advances the methodologies for assessing the cumulative effects of long-term ETE exposure on chronic cardiovascular outcomes.