| Background and objectiveChronic and noncommunicable diseases are the leading causes of death in the word,and blood pressure(BP)and body weight have become the main risk factor.Numerous studies have shown the benefits of physical activity(PA)in preventing and controlling BP and body weight.When people participate in PA,they are inevitably exposed to certain environments,in which the fine particulate matter with an aerodynamic diameter less than 2.5 μm(PM2.5)and greenspace exposure are likely to have a joint effect on BP and body weight with PA.The increased exposure to PM2.5 during PA may have harmful impacts on health,especially in highly polluted areas.Although some studies in Europe and the United States suggests that high PM2.5 exposure will not offset the benefits of PA on health,it remains a lack of evidence from highly pollutes regions.Greenspace,as a type of healthy supportive environment,may enhance the health benefits of PA,but related studies are limited and the joint effects of the two factors remain unclear.In addition,current studies on the joint effects of PA and environmental exposure have focused on the disease,while ignoring its effect on modifiable risk factors for disease.Therefore,based on the nationwide survey,this study aims to explore the joint associations of PA and environmental exposure with BP or body weight and two-dimensional exposure-response associations.MethodsThe health data in this study was from the China Hypertension Survey conducted in 20122015.PA was estimated as minutes of metabolic equivalent tasks per week(METmin/week),integrating domain,intensity,frequency and daily accumulated time of PA.PM2.5 exposure data was from the product of the Tracking Air Pollution in China,and weekly and annual mean values of PM2.5 concentrations were calculated.Greenspace exposure data was from the Vegetation Index Product and Land Cover Type Product,which provided by the Moderate Resolution Imaging Spectroradiometer.The monthly and annual average of the Normalized Difference Vegetation Index(NDVI)and Enhanced Vegetation Index were used to evaluate the overall greenspace exposure level,and the annual average of the proportion of forest,grasslands,and croplands were used to estimate the specific types of greenspace exposure,with larger values indicating higher greenspace exposure.The environmental exposure data had a spatial resolution of 10km×10km.This study mainly focused on BP,followed by body weight,which was assessed using Body Mass Index(BMI).A total of 203,108 adults aged≥18 years were included to analyze the association between PA and BP,with 201,274 adults for PA-BMI association in full population and 87,763 adults in overweight/obese population.Generalized linear regressions were used to estimate the associations between PA,environmental exposure and BP/BMI,and interactions between these two factors.The spline function was used to analyze the expose-response relationship between PA,environmental exposure and BP/BMI.The tensor product smooth function was used to fit the two-dimensional exposure-response association of PA and environmental exposure with BP/BMI.ResultsAmong the 203,108 participants,the mean(standard deviation,SD)age was 48.3(18.2)years.The median(interquartile range)values of total PA,4-week average PM2.5 concentration,and contemporaneous NDVI were 3213.0(1188.0,5733.0)MET-min/week,47.8(32.8,69.2)μg/m3,and 0.479(0.334,0.635),respectively.The mean(SD)values of SBP,DBP and BMI were 127.6(19.3)mmHg,75.3(10.6)mmHg,and 23.7(3.5)kg/m2,respectively.Compared with those in the lowest level of the total PA category(0 MET-min/week),the highest level of the total PA category(≥3000 MET-min/week)was associated with a 0.48(95%[Confidence Interval,CI]:0.22,0.74)mmHg decrease in systolic BP(SBP),and 1.09(95%CI:0.93,1.25)mmHg decrease in diastolic BP(DBP),respectively.With the increase of total PA,the SBP first decreased and then increased,while the DBP decreased overall.Total PA was positively associated with BMI.However,a negative association between PA and BMI was observed among participants with overweight/obese,with a flat change in BMI at lower activity levels and a significant decline in BMI at higher levels of total PA.Every 10 μg/m3 increment in the 4-week average PM2.5 exposure concentrations was significantly associated with a 0.42(95%CI:0.36,0.47)mmHg increase in SBP and a 0.21(95%CI:0.18,0.24)mmHg increase in DBP,respectively.PM2.5 exposure was positively associated with BMI.Every 0.1 increment in the contemporaneous NDVI was significantly associated with a 0.70(95%CI:0.67,0.74)mmHg decrease in SBP and a 0.27(95%CI:0.24,0.29)mmHg decrease in DBP,respectively.NDVI was negatively associated with BMI.The forest and grasslands exposure were negatively associated with BP or BMI,while croplands exposure was positively associated with BP or BMI.The exposureresponse relationships between PM2.5 exposure,greenspace exposure and BP or BMI were nonlinear.Compared with participants performing 0 MET-min/week in the low PM2.5 exposure group,≥3000 MET-min/week group was associated with a decrease in BP under low PM2.5 exposure;while under high PM2.5 exposure,it was associated with an increase in SBP,but not with DBP.When PM2.5 exposure concentration was about>25 μg/m3,the joint exposure of total PA and PM2.5 exposure was associated with an increase in SBP.Among participants with overweight/obese,when PM2.5 exposure concentration was about>80μg/m3 and total PA was about<7500 MET-min/week,the joint exposure of total PA and PM2.5 exposure was associated with an increase in BMI.Compared with participants performing 0 MET-min/week in the low contemporaneous NDVI group,≥3000 MET-min/week group was associated with a decrease in DBP but not SBP under low contemporaneous NDVI;while under high contemporaneous NDVI,it was associated with a decrease in BP.Compared with participants performing 0 MET-min/week in the low forest exposure group,≥3000 MET-min/week group was associated with a larger decrease in BP under high forest exposure than under low forest exposure.Similar results were observed for grasslands exposure.Compared with participants performing 0 METmin/week in the low croplands exposure group,≥3000 MET-min/week group was associated with a decrease in BP under low croplands exposure;while under high croplands exposure,it was associated with an increase in BP.Among participants with overweight/obese,compared with participants performing 0 MET-min/week in the low annual average NDVI group,≥3000 MET-min/week group was associated with a 0.12(95%CI:0.02,0.21)kg/m2 decrease in BMI under low annual average NDVI;while under high annual average NDVI,it was associated with a 0.34(95%CI:0.25,0.44)kg/m2 decrease in BMI.ConclusionDoing some PA,which are not meeting the recommendations,shows the more benefits on BP than doing none among Chinese general population.Moreover,people who have achieved total PA levels 5-7 times higher than the current recommended minimum level may have much lower BP levels.However,under high PM2.5 exposure,the benefits of PA on BP are attenuated,and the benefits of PA on SBP are offset by PM2.5 exposure about>25μg/m3.The benefits of PA on BP are enhanced by high greenspace exposure,but different types of greenspace show different effects on the benefits of total PA on BP.Although there is a positive association between total PA and BMI,a negative association between total PA and BMI for participants with overweight/obese is observed.For overweight/obese individuals,the benefits of total PA on BMI are offset at PM2.5 exposure about>80 μg/m3 and total PA about<7500 MET-min/week.The benefits of total PA on BMI are enhanced by high greenspace exposure,but the effects of different types of greenspace on the benefits of total PA on BMI varies.Our findings suggest that to improve PA level not only depends on changes in personal behavior,but also requires the construction of healthy supportive environment,including environment quality improvement and greenspace planning.Moreover,scientific PA arrangements should be appropriately adjusted according to changes in environmental exposure. |
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