Both low and high temperature may increase the risk of stroke mortality

Abstract

Objective: To examine temperature in relation to stroke mortality in a multicity time series study in China.Methods: We obtained data on daily temperature and mortality from 8 large cities in China. We used quasi-Poisson generalized additive models and distributed lag nonlinear models to estimate the accumulative effects of temperature on stroke mortality across multiple days, adjusting for long-term and seasonal trends, day of the week, air pollution, and relative humidity. We applied the Bayesian hierarchical model to pool city-specific effect estimates.Results: Both cold and hot temperatures were associated with increased risk of stroke mortality.The potential effect of cold temperature might last more than 2 weeks. The pooled relative risks of extreme cold (first percentile of temperature) and cold (10th percentile of temperature) temperatures over lags 0-14 days were 1.39 (95% posterior intervals [PI] 1.18-1.64) and 1.11 (95% PI 1.06-1.17), compared with the 25th percentile of temperature. In contrast, the effect of hot temperature was more immediate. The relative risks of stroke mortality over lags 0-3 days were 1.06 (95% PI 1.02-1.10) for extreme hot temperature (99th percentile of temperature) and 1.14 (95% PI 1.05-1.24) for hot temperature (90th percentile of temperature), compared with the 75th percentile of temperature.Conclusions: This study showed that both cold and hot temperatures were associated with increased risk of stroke mortality in China. Our findings may have important implications for stroke prevention in China. Stroke is one of the leading causes of death and disability worldwide.1 In contrast to developed countries, where stroke incidence declined by 42% over the last 4 decades, stroke incidence in developing countries doubled, surpassing that from developed countries.2 China is the largest developing country in the world and stroke burden is disproportionately high. In China, stroke mortality accounts for 19% of the total mortality, more than twice the mortality from ischemic heart disease (8%).3 Moreover, stroke patients in China have higher fatality than patients from developed countries. 4 Stroke has substantial medical, public health, and economic impacts in China.To reduce the burden of stroke, it is crucial to identify modifiable risk factors. It is wellknown that some traditional cerebrovascular risk factors, including hypertension, high cholesterol levels, obesity, smoking, and alcohol consumption, increased the risk for stroke. 5 However, the potential relationships of environmental risk factors and stroke have not been adequately studied in China.

Temperature and Cardiovascular Mortality Associations in Four Southern Chinese Cities: A Time-Series Study Using a Distributed Lag Non-Linear Model

“…Furthermore, the relative risk of cold-related CVD mortality was higher for females than males, while men were more sensitive to extreme heat temperatures than women. This finding is consistent with previous studies [27,[57][58][59]. The meta-analysis also showed that female CVD mortality was influenced more by cold temperatures, while males were more affected by hot temperatures (Figure 3).…”

Meteorological Parameters and the Onset of Chest Pain in Subjects with Acute ST-Elevation Myocardial Infarction: an Eight-Year, Single-Center Study in China

“…No significant heat effects were observed. However, the above results were based on daily data regarding AMI hospitalizations and mean temperatures, which were collected between 2000 and 2009 in three warm-climate Asian cities [9]. In the present study, both temperature data and data regarding the occurrence of STEMI were collected at 6 hour intervals from 2003 to 2010, and the results indicated that although the immediate association between temperature and STEMI (lag 0) is consistently positive (higher temperatures are associated with a higher incidence of STEMI) long-term associations (lags 0-7, lags 0-14) appear as a U-shaped curve, as both high and low temperatures are associated with a higher risk of STEMI.…”

“…Therefore, the relative risks ( RRs ) and 95% confidence intervals ( CI ) for the onset of STEMI at the first percentile, 10th percentile, 25th percentile, 75th percentile, 90th percentile, and 99th percentile of meteorological conditions were calculated and compared with the 50th percentile of meteorological conditions. The selection of these cutoffs for calculating the RRs and 95% CIs was made based on a previous study [9]. …”

Emergency Cardiovascular Hospitalization Risk Attributable to Cold Temperatures in Hong Kong

“…The extreme hot and moderate hot was defined using the 99th percentile as the cut-off point. 17 Air pollution concentrations in the same period were obtained from the Environmental Protection Department of Hong Kong. We calculated the daily 24-hour mean concentrations of nitrogen dioxide (NO 2 ) and particulate matter with aerodynamic diameter <10 μm (PM 10 ) and daytime 8-hour (10:00-17:00) mean concentrations of O 3 for each general monitoring, and then averaged them across the 10 stations.…”