Differentiating the impact of non-optimum temperature and temperature variability on cause-specific cerebrovascular mortality: An individual-level, case-crossover study in Shanghai, China.

BACKGROUND

Cerebrovascular mortality exhibits seasonal variation, but the roles of temperature and temperature variability (TV) in cause-specific cerebrovascular mortality remain unclear.

METHODS

This individual-level time-stratified case-crossover research collected individual cerebrovascular death records during 2005-2021 in Shanghai, China. TV was calculated as the standard deviation of daily minimum and maximum temperature over consecutive days. Conditional logistic regression models combined with distributed lag nonlinear models were utilized to evaluate the cumulative exposure-response associations.

RESULTS

Based on a total of 388,823 cerebrovascular deaths, we found that exposure to extreme cold, extreme heat, and greater TV was significantly related to increased cause-specific cerebrovascular mortality. Extreme cold exhibited the strongest impact on hemorrhagic stroke [relative risk (RR) = 1.84; 95 % confidence interval (CI): 1.50, 2.26], followed by hemorrhagic stroke sequelae [1.75 (95 % CI: 1.25, 2.45)] and cerebrovascular sequelae [1.71 (95 % CI: 1.58, 1.86)]. Extreme heat showed the largest effect on cerebrovascular sequelae [1.35 (95 % CI: 1.29, 1.41)], followed by ischemic stroke sequelae [1.34 (95 % CI: 1.28, 1.41)]. TV was associated with the largest percentage increase in ischemic stroke sequelae [2.12 % (95 % CI: 1.35 %, 2.90 %)], followed by cerebrovascular sequelae [1.95 % (95 % CI: 1.23 %, 2.68 %)]. Stratified analyses revealed stronger associations in the elders, singles, and those with low education.

CONCLUSIONS

This case-crossover study provides the first-hand evidence that extreme temperatures and TV may elevate the risk of cause-specific cerebrovascular mortality, which underscore the urgency of implementing targeted protective measures for cerebrovascular patients facing extreme weather events, particularly among aging populations in megacities under climate change.