| Background and objectivesCardiovascular disease(CVD)is the leading cause of disease burden and mortality worldwide.Commuting-related physical activity is an important part of daily physical activity.Research evidences based on populations in western countries showed that active commuting was associated with lower risks of CVD incidence and mortality.However,choosing an active commuting mode might increase individual level of outdoor air pollution exposure.Evidences from western countries showed that the cardiovascular health effects of active commuting were not counteracted by the exposure to air pollutants.Nevertheless,the results from western countries cannot be extrapolated directly to Chinese population due to differences in trends of commuting modes,environmental factors,and disease spectrum.More research evidences are urgently needed for the effect of commuting mode on cardiovascular health,and the modification effect of severe air pollution on the cardiovascular health effect of active commuting among Chinese population.Based on data from large perspective cohorts in China,this study aimed to explore the associations of commuting mode and risk of CVD and mortality as well as all-cause mortality,and to further investigate the cardiovascular beneficial effect of active commuting under different levels of fine particulate matter(PM2.5)and the interaction between ambient PM2.5 and commuting mode,so as to provide scientific evidences for choice of commuting mode under the high level of air pollution in China,the promotion of healthy lifestyle,and primary prevention of CVD.Subjects and MethodsParticipants of this study were from three prospective population cohorts of the Prediction for Atherosclerotic Cardiovascular Disease Risk in China(China-PAR)project,which were the China Multi-Center Collaborative Study of Cardiovascular Epidemiology-1998(ChinaMUCA-1998),the International Collaborative Study of Cardiovascular Disease in Asia(InterASIA),and the Community Intervention of Metabolic Syndrome in China&Chinese Family Health Study(CIMIC).The baseline of this study was set at 2007-2008.A total of 104,957 participants completed the survey.Baseline information of participants were collected by trained and qualified staff using standard questionnaires and operating manuals,including demographic information,commuting mode,lifestyle,and disease conditions,as well as physical examination and blood biochemical tests.During 2012 to 2015,follow-up surveys were conducted on the three cohorts.Questionnaire interview and physical examination that were consistent with the baseline were used to collect information of study participants.The information of morbidity and mortality were obtained through interviewing participants or their proxies,and through local hospitals,disease control and prevention center and police stations.The individual PM2.5 exposure concentration of participants during 2007-2015 were evaluated by advanced satellite technology.The main outcomes of this study were CVD incidence and all-cause mortality.CVD incidence comprised non-fatal acute myocardial infarction,fatal coronary heart disease(CHD),and non-fatal or fatal stroke,etc.All-cause mortality comprised death caused by any causes.Participants were divided into three groups according to their commuting modes,including the non-active commuting group,walking group,and cycling group.Cox proportional hazard regression models were used to analyze the hazard ratio(HR)and 95%confidence interval(95%CI)for associations of commuting modes and CVD incidence,mortality,as well as all-cause mortality.The difference of the area under the survival curve was used to estimate the CVD-free year gained and life year gained.Subgroup analyses were conducted according to baseline characteristics,so as to explore the cardiovascular health effects of active commuting in different subgroups of participants.Besides,this study investigated the cardiovascular health effect of active commuting under different levels of PM2.5 exposure.Furthermore,this study divided the participants into 6 groups according to commuting mode(non-active,walking and cycling)and median of ambient PM2.5 level(<61?g/m3 and ?61?g/m3),and the non-active commuting group exposed to higher PM2.5 level was used as reference to explore the joint effects of commuting and ambient PM2.5 level on CVD incidence,mortality,and all-cause mortality.ResultsAfter excluding participants who were with CVD,unemployed or retired,with missing commuting information and lost to follow-up,76,176 participants were included finally,of which 38,111 participants were under lower level of PM2.5 and 38,065 were under higher level of PM2.5.During an average follow-up period of 5.9 years(448,499 person-years),a total of 2230 cases of CVD events,918 CVD deaths,and 2777 all-cause deaths were observed.Among them,876 cases of CVD events,374 CVD deaths,and 1302 all-cause deaths were observed among participants under lower level of PM2.5;1354 cases of CVD events,544 CVD deaths,and 1475 all-cause deaths were observed among participants under higher level of PM2.5.After multivariate adjustment,compared with non-active commuters,the HR(95%CI)of CVD incidence,mortality and all-cause mortality in walking commuters were 0.95(0.85-1.05),0.80(0.68-0.95)and 0.79(0.72-0.87),respectively;the corresponding HRs(95%CI)of cycling commuters were 0.71(0.62-0.82),0.58(0.46-0.73)and 0.67(0.59-0.76),respectively.Active commuting was significantly associated with postponement of CVD incidence and longer life expectancy.For example,45-year-old walking commuters were estimated to have 2.16 years(95%CI:1.35-3.10 years)of life years gained.Cycling commuters were estimated to have 3.24 years(95%CI:2.33-4.22 years)of CVD-free years gained and 3.71 years(95%CI:2.68-4.61 years)of life years gained.However,no significant CVD-free year gained was observed among walking commuters.Subgroup analyses showed that the cardiovascular protective effect of active commuting was more significantly among participants who were over 60 years old,non-smokers,non-drinkers,and those who had not developed dyslipidemia.Among participants under lower PM2.5 exposure,after multivariate adjustment,compared with non-active commuters,the HRs(95%CIs)of CVD incidence,mortality,and all-cause mortality in walking commuters were 0.90(0.72-1.13)and 0.78(0.54-1.10)and 0.77(0.64-0.93),respectively;the corresponding HRs(95%CIs)of cycling commuters were 0.71(0.55-0.91),0.43(0.27-0.69)and 0.48(0.38-0.59),respectively.Active commuting was associated with postponement of CVD incidence and longer life expectancy.For example,45-year-old walking commuters were estimated to have 1.82 years(95%CI:0.45-3.13 years)of CVD-free years gained,3.46 years(95%CI:1.94-5.04 years)of life years gained;Cycling commuters were estimated to have 3.61 years(95%CI:2.48-4.85 years)of CVD-free years gained and 6.74 years(95%CI:5.34-8.04 years)of life years gained.Among participants under higher PM2.5 exposure,after multivariate adjustment,compared with non-active commuters,the HRs(95%CIs)of CVD incidence,mortality,and all-cause mortality in walking commuters were 1.04(0.92-1.17),1.01(0.84-1.21)and 0.93(0.83-1.04),respectively;the corresponding HRs(95%CIs)of cycling commuters were 0.91(0.76-1.08),0.93(0.72-1.21)and 0.99(0.85-1.15),respectively.The postponement of CVD incidence and longer life expectancy by active commuting was alleviated or counteracted by higher PM2.5 exposure.For example,45-year-old cycling commuters were estimated to have only 1.72 years(95%Cl:0.38-3.14 years)of CVD-free years gained,while no significant CVD-free or life years gained was observed.The joint association analysis found that,compared with non-active commuters under higher PM2.5 exposure,cycling commuters under lower PM2.5 exposure had the lowest risk of CVD incidence,mortality,and all-cause mortality,and the HRs(95%CIs)were 0.26(0.20-0.35)and 0.14(0.08-0.24)And 0.22(0.17-0.29),with the Interation of 0.055,0.001 and<0.001,respectively.ConclusionsThis study clarified the associations of commuting mode and CVD incidence,mortality,and all-cause mortality among Chinese population,suggesting that choosing an active commuting mode,especially cycling,could reduce the risk of CVD incidence,mortality,and all-cause mortality,as well as delay the onset of CVD and prolong life expectancy among Chinese population.However,long-term exposure to higher level of ambient PM2.5 would alleviate or even counteract the cardiovascular beneficial effects of active commuting. |
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