Exposure to greenness modifies the association between extreme temperature events and ischemic stroke recurrence in Tianjin, China

Few studies have found an association between extreme temperature events and an increased risk of recurrent ischemic stroke (IS). We examined associations between extreme temperature events (heat waves, cold spells) and recurrent IS risk in Tianjin, China (2019–2020), using a time-stratified case-crossover design, while evaluating greenness’s moderating role. Significant heat wave effects peaked at lag 8, with severe intensity events increasing IS recurrence risk by 39.8% (OR = 1.398, 95% CI:1.032–1.894). Cold spell impacts peaked at lag 3, with moderate intensity cold spells elevating risk by 20.3% (OR = 1.203, 95% CI: 1.052–1.377) and severe intensity cold spells elevating risk by 98.2% (OR = 1.982, 95% CI: 1.407–2.791). Greenness modified these associations: low-greenness areas strengthened heat wave effects(lag9:OR = 2.309,95%CI:1.024–5.209) but weakened cold spell impacts(OR = 1.557,95%CI:1.037–2.340), whereas high-greenness areas attenuated heat wave links(lag8:OR = 1.402,95%CI:1.022–1.924) and nullified cold spell associations. Age and sex disparities emerged – younger individuals and males showed higher susceptibility to heat waves, while older individuals and males were more vulnerable to cold spells. The findings highlight greenness as a potential modifier of extreme temperature events-related IS recurrence risks and underscore demographic-specific vulnerabilities.