| Background and ObjectiveUnder the background of global climate change,the temperature had increased dramatically.Not only that,the frequency of extreme weather events is also increasing.Temperature and cold spell had been proved to be quite related to non-accidental mortality.At present,many related studies were conducted in the lower altitude areas,but there were few studies in the plateau area like Tibet.However,previous studies on the Tibet only included deaths in some districts and counties,and there was almost no study on the mortality burden.Therefore,this study will evaluate the relationship between the temperature and non-accidental mortality and the mortality burden in Tibet Autonomous region,and then evaluate the impact of cold spell events on non-accidental mortality and the mortality burden of cold spell events.MethodsBased on the surveillance data of residents death causes in Tibet Autonomous region from 2013 to 2019,a case-crossover design with time stratification was adopted,and the exposure-response relationship between daily mean temperature and non-accidental mortality was analyzed by conditional logistic regression model.Based on the exposure-response relationship,the excess risk for every 1℃ change in temperature was obtained,and the attributable fraction was calculated to evaluate the mortality burden caused by temperature.Stratified analysis was conducted according to population(gender,age),disease classification and area.Then extracted data of cold season(December,January to March)in Tibet during the study period,analyzed the impact of cold spell events on non-accidental mortality,and calculated the attributable fraction to evaluate the mortality burden caused by cold spell,and stratified analysis was conducted according to gender,age,disease and area.ResultsFrom 2013 to 2019,the exposure response relationship between daily mean temperature and non-accidental mortality in Tibet Autonomous region showed that mortality risk increased with the decrease of air temperature,which mean cold effect was only observed.A 1℃ decrease in temperature was associated with a 2.01%(95%CI:0.94%～3.07%)increased in non-accidental mortality,while male was 2.05%(95%CI:0.62%～3.47%),female was 1.96%(95%CI:0.52%～3.56%);people under 65 years old was 1.45%(95%CI:-0.10%～2.98%),people over 65 years old was 2.52%(95%CI:1.04%～3.99%);cardiovascular disease was 2.65%(95%CI:1.03%～4.24%),and respiratory disease was 2.18%(95%CI:-0.14%～4.44%).The attributable number of non-accidental mortality was 5340(95%CI:2719～7528),and the attributable fraction(AF)was 20.50%(95%CI:10.44%～28.91%),some attributable fractions were higher in specific subgroups in which male was 20.72%,the elderly was 23.33%,cardiovascular diseases was 26.07%and northwest was 29.68%.Totally,the cumulative excess risk(CER)of cold spell in Tibet from 2013 to 2019 was 48.8%(95%CI:19.2%～85.7%),some CER were higher in specific subgroups,in which female was 52.2%(95%CI:9.5%～111.5%),people under 65 years old was 69.8%(95%CI:22.3%～135.8%),respiratory disease was 41.0%(95%CI:-25.0%～165.2%),and northwest Tibet was 108.4%(95%CI:46.3%～196.8%).The AF of non-accidental mortality caused by cold spell in Tibet was 4.41%,while 2.50%in southeast,7.03%in northwest,4.21%in male,4.61%in female,5.61%in people under 65 years old,3.36%in people over 65 years old,3.11%in cardiovascular disease and 3.59%in respiratory disease.ConclusionsBoth low temperature and cold spell led to increasement of mortality risk,although mortality risk was lower than the study conducted in the low altitude areas,but the mortality burden was much higher.There was great heterogeneity between southeastern Tibet and northwestern Tibet,of which attributable fraction was higher.For the results of temperature analysis,male,people over 65 years old,patients with cardiovascular and respiratory diseases and people in northwest Tibet may be vulnerable to low temperature.For the cold spell results,women,people under 65 years old and people in northwest may be vulnerable population. |
