Total and cause-specific mortality attributable to cold spells in China:A multicity and multicounty study

Climate change has resulted in an increase in the frequency and intensity of extreme cold weather events,but few multicity or multicounty researches have explored the association between cold spells and mortality risk and burden.We collected daily data on climate,sociodemo-graphic factors and mortality in 18 cities/counties across 11 geographical regions for the period of November to March 2014-2018.A distributed lag nonlinear model was used to examine the association between cold spells and mortality after adjustment for confounding factors.Twelve definitions of cold spells were used.Multi-meta regression analysis was applied to pool the impacts over different regions.Cold spells were significantly associated with all-cause mortality at lag 0-21(CRR:1.38,95%CI:1.21,1.57).In addition to respiratory diseases and cir-culatory system diseases,digestive,endocrine and nervous system diseases and injury were also affected by cold spells.The magnitude of the impacts of cold spells on mortality varied among the diseases investigated,with the highest risk estimate found for influenza and pneumonia(CRR:2.00,95%CI:1.45,2.76)and the lowest estimate found for injury(CRR:1.26,95%CI:1.09,1.46).The fraction of all-cause mortality attributable to cold spells was 2.31%(95%CI:0.90%,3.46%).Among the regional differences,the attributable burden of all-cause mortality was higher in rural areas and subtropical monsoon climate zone,with attributable fractions of 2.85%(95%CI:1.23%,4.11%)and 3.36%(95%CI:0.55%,5.35%),respectively.Cold spells increased mortality from a range of diseases.Women,older adults and residents of rural areas and subtropical monsoon climate zone were more vulnerable to cold spells impacts.The findings may help to formulate preventive strategies and early warning response plans to reduce mortality burden of extreme cold events.

Defining region-specific heatwave in China based on a novel concept of “avoidable mortality for each temperature unit decrease”

The distribution of temperature and temperature-health association varied largely across different regions in China,a region-specific definition for heatwave was therefore needed.We collected the data on daily mortality,meteorological factors and air pollution in 84 Chinese cities during 2013–2016,which was divided into seven regions.Based on the association between daily maximum temperature and mortality in each city in a threshold distributed lag non-linear model,where the threshold was defined as the temperature corresponding to the lowest mortality risk,we calculated the number of deaths that could be avoided for 1℃ decrease in maximum temperature under different thresholds,then a random-effect meta-analysis was used to generate regional results,in which the temperature with the highest avoidable mortality number for 1℃ decrease was considered as the most appropriate heatwave definition.We observed an immediate detrimental effect of high temperature within three lag days.Our analysis suggested to use 29.5℃,31.5℃,29.0℃,31.5℃,30.0℃,and 28.5℃ as the heatwave standard for east,north,northeast,central,south,and southwest region,with the avoidable mortality number of 1.54(95%Confidence interval(CI):0.88,2.19),0.55(95%CI:0.16,0.94),0.59(95%CI:0.32,0.86),1.14(95%CI:0.68,1.59),1.22(95%CI:0.54,1.90),and 0.78(95%CI:0.01,1.55),respectively,while the estimated number 0.19(95%CI:−0.02,0.40)in northwest region was not statistically significant.The concept of‘avoidable mortality for 1℃ decrease’was proposed to define the heatwave event,and varied maximum temperature between 28.5 and 31.5℃ was suggested for region-specific heatwave definition in China.

Ambient Temperature and Years of Life Lost:A National Study in China

Although numerous studies have investigated premature deaths attributable to temperature,effects of temperature on years of life lost(YLL)remain unclear.We estimated the relationship between temperatures and YLL,and quantified the YLL per death caused by temperature in China.We collected daily meteorological and mortality data,and calculated the daily YLL values for 364 locations(2013–2017 in Yunnan,Guangdong,Hunan,Zhejiang,and Jilin provinces,and 2006–2011 in other locations)in China.A time-series design with a distributed lag nonlinear model was first employed to estimate the location-specific associations between temperature and YLL rates(YLL/100,000 population),and a multivariate meta-analysis model was used to pool location-specific associations.Then,YLL per death caused by temperatures was calculated.The temperature and YLL rates consistently showed U-shaped associations.A mean of 1.02(95%confidence interval:0.67,1.37)YLL per death was attributable to temperature.Cold temperature caused 0.98 YLL per death with most from moderate cold(0.84).The mean YLL per death was higher in those with cardiovascular diseases(1.14),males(1.15),younger age categories(1.31 in people aged 65–74 years),and in central China(1.34)than in those with respiratory diseases(0.47),females(0.87),older people(0.85 in people R75 years old),and northern China(0.64)or southern China(1.19).The mortality burden was modified by annual temperature and temperature variability,relative humidity,latitude,longitude,altitude,education attainment,and central heating use.Temperatures caused substantial YLL per death in China,which was modified by demographic and regional characteristics.