Objective:To assess the effect of ambient temperature on mortalities of ischemic stroke and hemorrhagic stroke in Beijing, China.Methods:The stroke mortality surveillance data and meteorological data in Beijing from January 1, 2014 to December 31, 2019 were collected. Distributed lag nonlinear models were used to estimate the cumulative effects of ambient temperature on stroke mortality, including ischemic stroke and hemorrhagic stroke after adjusting for temporal trend, day of week, air pollution, and relative humidity. Stratified analysis was conducted to evaluate whether sex and age modify the effect.Results:From 2014 to 2019, a total of 99 222 stroke deaths occurred in Beijing, including 69 327 ischemic stroke deaths, 24 954 hemorrhagic stroke deaths, and 4 941 unspecific stroke deaths. Using distributed lag nonlinear models, it was found the effect of temperature on stroke mortality was nonlinear and lagged. The ischemic stroke mortality risk analysis shows that with the minimum ambient temperature (MMT) for mortality (10.0 ℃) as reference, the effect of extreme low temperature (-6.2 ℃) was lagged and the relative risk ( RR) was highest at lag 0-21 days ( RR=1.26, 95% CI:1.04-1.51). The effect of extreme high temperature occurred with a lag of 0-3 days, and the cumulative RR value was 2.13 (95% CI: 1.72-2.62) at lag 0-14 days. The hemorrhagic stroke mortality risk analysis shows that with the MMT for mortality (28.0 ℃) as reference, the RR of extreme low temperature on stroke mortality was highest at lag 0-21 days ( RR=2.14, 95% CI: 1.23-3.70), and the effect of extreme high ambient temperature was short and only has statistical significance in the cumulative effect with a lag of 0-3 days ( RR=1.14, 95% CI: 1.01-1.28). Stratified analysis revealed that the effects of extreme and moderate low ambient temperature on hemorrhagic stroke death were higher in women compared to men, and the difference is statistically significant. Extreme high ambient temperature might increase the risk of ischemic stroke deaths in populations of different genders and age groups. Conclusions:The effect of low ambient temperature on ischemic stroke mortality was lagged, and the effect on hemorrhagic stroke was persistent. The effect of high ambient temperature on ischemic stroke mortality was persistent, but more transient on hemorrhagic stroke mortality. Sex and age might modify the effect of ambient temperature on stroke mortality.

ObjectiveTo observe the effect and mechanism of curcumin on cognitive function in the mouse model of low oxygen-induced chronic nerve injury. MethodEighty male C57BL/6 mice were randomized into eight groups： control， low-， medium-， and high-dose （100， 200， and 300 mg·kg^-1， respectively） curcumin， model， model + low-dose curcumin， model + medium-dose curcumin， and model + high-dose curcumin groups （n=10）. The mouse model of low oxygen-induced nerve injury was prepared by continuous stimulation with simulated oxygen concentration at Lhasa altitude （13% O₂ at about 3 700 m） for 14 days. After the completion of modeling， mice in the six curcumin groups were administrated with curcumin at corresponding doses by gavage， while those in the control group and the model group were administrated with the same amount of normal saline once a day for one week. After that， open field， novel object recognition， and Morris water maze tests were carried out to reveal the behavioral changes of mice. The morphological changes of the hippocampus were observed by hematoxylin-eosin staining. The mRNA levels of interleukin （IL）-6 and tumor necrosis factor （TNF）-α in the hippocampus and peripheral blood of mice were determined by real-time PCR. The activation of microglia in the hippocampus was observed by Iba-1 staining. The protein levels of brain-derived neurotrophic factor （BDNF） and cAMP-response element-binding protein （CREB） in the hippocampus were determined by Western blot. ResultCompared with the control group， the model group showed decreased new object recognition rate （P<0.01）， extended time to find the platform （P<0.01）， and reduced platform crossings （P<0.05）， which proved that the cognitive function of mice was impaired. Compared with model group， the model + medium-dose curcumin group showed increased new object recognition rate， shortened time to find the platform， and increased platform crossings （P<0.05，P<0.01）. Moreover， the application of curcumin repaired the abnormal morphological and structural changes in the hippocampus， reduced the inflammatory cytokine levels and activation of microglia， and upregulated the expression of CREB and BDNF （P<0.05）. ConclusionCurcumin demonstrates a therapeutic effect on low oxygen-induced cognitive decline， which provide a potential cure for treating chronic brain injury induced by high-altitude low oxygen in clinical practice.