Associations Between Indoor Cooking With Biomass Fuels And Hypertension And Cognitive Function Among Old Chinese Adults

Objective: Currently,China accounts for about one fifth of the world’s total population;however,due to a drastic decline in mortality and birth rates,China is rapidly transforming into an aging country.It is predicted that from 2010 to 2050,the Chinese elderly population will rise from 111 million(8.2% of the total population)to 400million(26.9% of the total population).This rapid increase entails that China will have one of the highest proportions of elderly persons in the world.Notably,an aging population with longer life expectancy will inevitably give rise to a host of health challenges.Consequently,greater attention should be paid to age-related diseases.Cardiovascular disease is the first cause of death in the world and hypertension is one of the most important risk factors for cardiovascular disease;the cognitive function of the elderly declines with age,and cognitive impairment seriously harms the physical and mental health of the elderly.Air pollution is one of the most concerned environmental risk factors in recent years.This study described the biomass fuels using for cooking and energy conversion of the elderly in various regions of my country,and discussed the factors affecting the elderly’s choice of biomass fuel cooking and energy conversion.This study analyzed the associations between indoor air pollution caused by cooking with biomass fuels and hypertension,cognitive impairment and cognitive decline in the elderly.This study explores the effects of indoor air pollution on hypertension and cognitive function to prevent the occurrence of hypertension and cognitive impairment in the elderly,and provides references for formulating intervention strategies for age-related diseases.Methods: The data was obtained from the Chinese Longitudinal Healthy Longevity Survey(CLHLS).The subjects of CLHLS’s survey are elderly people aged 65 years and older.Cooking with straw,firewood or charcoal was considered to primarily use biomass fuels and cooking with gas,solar energy or electricity was considered to primarily use clean fuels.A multiple logistic regression model was used to analyze the influencing factors of biomass fuel use and self-reported conversion between biomass fuels and clean fuels.Two conversion methods were included,switching from clean fuels to biomass fuels and switching from biomass fuels to clean fuels.We explored the associations between biomass fuel use and hypertension and cognitive function using the Cox proportional hazards model and examined the relationships of biomass fuel use with blood pressure measures and cognitive scores using the generalized estimating equation.Additionally,we examined the effect of switching cooking fuels on hypertension and cognitive function.Results: Our results demonstrat that 43.8% of the elderly use firewood for cooking,and26.4% and 12.8% of the elderly use gas and induction cookers for cooking.71.8% of rural elderly people use biomass fuels for cooking,while urban elderly people mainly use clean fuels for cooking.Between 2011 and 2014,13.9% of the elderly switched from clean fuels to biomass fuels for cooking,and 31.1% of the elderly switched from biomass fuels to clean fuels for cooking.Gender,residence,education level,marital status,regular exercise,BMI,annual family income,heart disease,diabetes,hypertension,activity restriction and independent cooking were related to cooking with biomass fuels.Residence,regular exercise and annual household income were related to switching from clean fuels to biomass fuels for cooking.Residence,education level,marital status,regular exercise,annual family income,hypertension and cognitive impairment are related to switching from biomass fuels to clean fuels among the elderly.Among 3754 participants who were without hypertension,the mean(SD)age was 86.6(11.3)years old,and 47.5% of participants were men.Reported use of biomass fuel for cooking(50.2%)was associated with a higher risk of hypertension(incidence rate(IR)per 100 person-years: 13.15 versus 12.99,hazard ratio(HR): 1.15,95% CI: 1.01-1.31).Biomass fuel use was related to systolic blood pressure(SBP)(β: 1.10 mm Hg,95% CI:0.48-1.72),diastolic blood pressure(DBP)(β: 1.02 mm Hg,95% CI: 0.61-1.43)and mean arterial pressure(MAP)(β: 1.03 mm Hg,95% CI: 0.63-1.43)elevation.Compared with persistent clean fuel users,participants who reported switching from clean to biomass fuels for cooking had a noticeably higher risk of hypertension(HR: 1.49,95% CI: 1.16-1.90)and a higher SBP(β: 3.71 mm Hg,95% CI: 2.36-5.06),DBP(β: 2.44 mm Hg,95%CI: 1.57-3.32)and MAP(β: 2.86 mm Hg,95% CI: 2.03-3.70).Interaction and stratified analyses showed greater effect estimates of SBP and MAP in the oldest old people(≥85).Among 4047 participants who were without cognitive impairment,the mean(SD)age was 80.0(9.4)years old.Reported use of biomass fuel for cooking was associated with greater risk of cognitive impairment(HR: 1.33,95% CI: 1.13-1.55).In addition,biomass fuel use was related to a significant decrease in cognitive score(β:-0.68,95% CI:-0.98--0.38).Compared with persistent biomass fuel users,participants who reported switching from biomass fuels to clean fuels for cooking exhibited a noticeably lower risk of cognitive decline(HR: 0.79,95% CI: 0.66-0.94)and a higher cognitive score(β: 1.02,95%CI: 0.59-1.45).Higher risk of cognitive decline(HR: 1.41,95% CI: 1.09-1.83)and a lower cognitive score(β:-0.67,95% CI:-1.31--0.03)was also observed among participants who reported switching from clean to biomass fuels,as compared with persistent clean fuel users.Interaction and stratified analyses showed relatively poor cognitive function in men and participants who engaged in irregular exercise or were not living with family.Conclusion: 1.In rural households,biomass fuels were the predominant fuel used for cooking,while in urban households,clean fuels were the major fuel used for cooking among elderly.The use of biomass fuels and fuel switching were affected by residence,regular exercise,and annual household income.2.The use of biomass fuels for cooking was associated with greater hypertension risk and higher blood pressure measures,and the risk may be higher among those who switched from clean fuels to biomass fuels in the Chinese elderly population.3.The use of biomass fuels for cooking was associated with greater risk of cognitive impairment and cognitive decline and a lower cognitive score.In the Chinese elderly population,this risk may be lower for those switching from biomass fuels to clean fuels.