The impact of cold spells on mortality and effect modification by cold spell characteristics.

In China, the health impact of cold weather has received little attention, which limits our understanding of the health impacts of climate change. We collected daily mortality and meteorological data in 66 communities across China from 2006 to 2011. Within each community, we estimated the effect of cold spell exposure on mortality using a Distributed Lag Nonlinear Model (DLNM). We also examined the modification effect of cold spell characteristics (intensity, duration, and timing) and individual-specific factors (causes of death, age, gender and education). Meta-analysis method was finally used to estimate the overall effects. The overall cumulative excess risk (CER) of non-accidental mortality during cold spell days was 28.2% (95% CI: 21.4%, 35.3%) compared with non-cold spell days. There was a significant increase in mortality when the cold spell duration and intensity increased or occurred earlier in the season. Cold spell effects and effect modification by cold spell characteristics were more pronounced in south China. The elderly, people with low education level and those with respiratory diseases were generally more vulnerable to cold spells. Cold spells statistically significantly increase mortality risk in China, with greater effects in southern China. This effect is modified by cold spell characteristics and individual-level factors.

[Analysis of the impact of the socio-economic factors on temperature-mortality association in southern China].

OBJECTIVE: To explore the impact of the socio-economic factors on the temperature-mortality association in different cities in southern China. METHODS: Daily mortality registration data, meteorological data and air pollution data of the cities as Changsha and Kunming during 2006-2009, and cities as Guangzhou and Zhuhai during 2006-2010, were collected to explore modifying effects, stratified by age, gender, education and place of death, of socio-economic factors on the association between temperature and mortality, by distributed lag non-linear model. The accumulative effect of temperature-mortality were separately analyzed in each city, under the high temperature (0-3 days) and low temperature (0-20 days) situation. The association between temperature and mortality was evaluated by general linear threshold model. The above process was firstly adopted to analyze the impact in single city and then Meta analysis was applied to analyze the impact in several cities by effect-combine. RESULTS: The relationship between temperature and mortality in the four cities showed nonlinearity. The minimum mortality risk was separately 23.5 °C, 20.5 °C, 25.0 °C and 26.0 °C in Changsha, Kunming, Guangzhou and Zhuhai. The results of effect-combine showed that low-temperature (RR = 1.67, 95%CI:1.54-1.80) has a higher gross effect than high-temperature (RR = 1.11, 95%CI:1.01-1.18) on population. With the age increasing, risk of death increased both under high and low temperature situation, and the effect of low temperature was greater (RR = 1.83, 95%CI:1.65-2.04) for the elderly than it of high temperature (RR = 1.17, 95%CI:1.03-1.33). The mortality risk among females (cold and hot effects(95%CI) were 1.75(1.57-1.97) and 1.11(0.99-1.25), respectively)was higher than it among males (cold and hot effects(95%CI) were 1.59(1.45-1.77) and 1.11(1.03-1.19), respectively). Whereas the mortality risk on higher education population was significantly higher (cold and hot effects (95%CI) were 1.89(1.48-2.45)and 1.34(1.19-1.48), respectively) than it on other educated people. CONCLUSION: Age, gender, educational level and place of death showed modifying effects on the association between temperature and mortality. The elderly, women and highly educated people were vulnerable to the temperature influence on mortality.

The effect of heat waves on mortality and effect modifiers in four communities of Guangdong Province, China.

BACKGROUND: Heat waves have been reported to be associated with increased mortality; however, fewer studies have examined the effect modification by heat wave characteristics, individual characteristics and community characteristics. METHODS: This study investigated the effect of extreme heat on mortality in 2 urban and 2 rural communities in Guangdong Province, China during 2006-2010. The effect of extreme heat was divided into two parts: main effect due to high temperature and added effect due to prolonged heat for several consecutive days. A distributed lag non-linear model was used to calculate the relative risk with consideration of lag days and potential confounding factors. Separate models were further fit by individual characteristics (cause of death, age and gender) and heat wave characteristics (intensity, duration and timing), and potential effect modification of community characteristics was examined using a meta-regression, such as educational levels, percentage of the elderly, Gross Regional Domestic Product (GDP). RESULTS: The overall main effects (ER=8.2%, 95% CI: 3.4%, 13.2%) were greater than the added effects (ER=0.0%, 95% CI: -3.8%, 4.0%) on the current day. The main effect peaked at lag0-2, and was higher for the two rural areas compared to the two cities, for respiratory compared to cardiovascular mortality, for those ≥75 years old and for females. The modifying effects of heat wave characteristics and community characteristics on mortality were not statistically significant. CONCLUSION: This study suggests the effects of extreme heat were mainly driven by high temperature, which can be modified by some individual characteristics.

The effects of dust-haze on mortality are modified by seasons and individual characteristics in Guangzhou, China.

This study aimed to investigate the effects of dust-haze on mortality and to estimate the seasonal and individual-specific modification effects in Guangzhou, China. Mortality, air pollution and meteorological data were collected for 2006-2011. A dust-haze day was defined as daily visibility <10 km with relative humidity <90%. This definition was further divided into light (8-10 km), medium (5-8 km) and heavy dust-haze (<5 km). A distributed lag linear model (DLM) was employed. Light, medium and heavy dust-haze days were associated with increased mortality of 3.4%, 6.8% and 10.4% respectively, at a lag of 0-6 days. This effect was more pronounced during the cold season, for cardiovascular mortality (CVD), respiratory mortality (RESP), in males and people ≥60years. These effects became insignificant after adjustment for PM10. We concluded that dust-haze significantly increased mortality risk in Guangzhou, China, and this effect appears to be dominated by particulate mass and modified by season and individual-specific factors.

[Relationship between temperature and the risks of mortality in China: a Meta-analysis].

OBJECTIVE: To understand the effect of temperature on the risk of mortality and the modification effect of latitude, in China. METHODS: Relevant papers were searched and Meta-analysis was used to determine the exposure-response relationship for each health outcome which was associated with the exposure to temperature. Meta-regression analysis was used to evaluate the effect modification by latitude. RESULTS: Ten studies in 15 cities were included in the study. When temperature increased by one centigrade, the risks of mortality showed the following changes:deaths from non-accidental increased by 2% (95%CI:1%, 3%), from cardiovascular disease increased by 4% (95%CI:2%, 6%)and from the respiratory disease increased by 2% (95%CI:1%, 4%). As temperature decreased by one centigrade, the mortality risks of the following diseases showed the changes as: non-accidental death increased by 4% (95% CI:2%, 7%), cardiovascular disease increased by 4% (95%CI:1%, 7%)and the respiratory diseases increased by 2% (95%CI:0%, 4%). When latitude ranged from 0 to 25, 26 to 30, 31 to 39 degree or over 40 degrees, respectively and the temperature decreased by one centigrade, the mortality risks of the general population increased by 6.5% (95%CI:-2.7%, 15.6%), 5.8% (95% CI:2.4%, 9.3%),0.8% (95%CI:0.4%, 1.2%),0.5% (95%CI: -0.5%, 1.5%). As temperature increased by one centigrade, mortality risk of the general population increased by 0.6% (95%CI:-0.3%, 1.4%), 1.9% (95%CI:0.7%, 3.1%), 2.0% (95%CI:1.0%, 3.0%) and 5.8% (95% CI:-3.2%, 14.8%). As latitude increased by five degrees with high temperature, the mortality risk of general people increased by 0.3% (95% CI:0.1% ,0.8%) while decreased by 0.8% (95% CI:0.5%, 0.9%) under low temperature. CONCLUSION: In China, the mortality risk increased along with the changes of temperature. The adaptability to coldness among people living in high latitude areas seemed to be stronger than those living in other areas of latitudes. Who were more vulnerable to high temperature.