Association between solid fuel use and cognitive impairment: A cross-sectional and follow-up study in a middle-aged and older Chinese population

Household use of polluting cooking fuels and late-life cognitive function: A harmonized analysis of India, Mexico, and China

INTRODUCTION

Exposure to high levels of air pollution is associated with poor health, including worse cognitive function. Whereas many studies of cognition have assessed outdoor air pollution, we evaluate how exposure to air pollution from combustion of polluting household fuels relates with cognitive function using harmonized data from India, Mexico, and China.

MATERIALS & METHODS

We analyze adults age 50+ in three nationally representative studies of aging with common data collection methods: the 2017-2019 Longitudinal Aging Study in India (n = 50,532), 2015 Mexican Health and Aging Study (n = 12,883), and 2013 China Health and Retirement Longitudinal Study (n = 12,913). Use of polluting fuels was assessed by self-report of wood, coal, kerosene, crop residue, or dung for cooking. Cognitive function was measured by performance across several cognitive domains and summarized into a total cognition score. We used linear regression, by country, to test how polluting cooking fuel use relates with cognition adjusting for key demographic and socioeconomic factors.

RESULTS

Approximately 47%, 12%, and 48% of respondents in India, Mexico, and China, respectively, relied primarily on polluting cooking fuel, which was more common in rural areas. Using polluting cooking fuels was consistently associated with poorer cognitive function in all countries, independent of demographic and socioeconomic characteristics. Adjusted differences in cognitive function between individuals using polluting and clean cooking fuel were equivalent to differences observed between individuals who were 3 years of age apart in Mexico and China and 6 years of age apart in India. Across countries, associations between polluting cooking fuel use and poorer cognition were larger for women.

CONCLUSIONS

Results suggest that household air pollution from the use of polluting cooking fuel may play an important role in shaping cognitive outcomes of older adults in countries where reliance on polluting fuels for domestic energy needs still prevails. As these countries continue to age, public health efforts should seek to reduce reliance on these fuels.

All-Cause Mortality Risk Associated With Solid Fuel Use Among Chinese Elderly People: A National Retrospective Longitudinal Study

Background: The adverse health effects of air pollutants are widely reported, and the elderly are susceptible to toxic environments. This study aimed to evaluate the association between use of solid fuels for cooking and mortality among the elderly. Methods: A total of 5,732 and 3,869 participants from the Chinese Longitudinal Healthy Longevity Survey were enrolled in two (2014 and 2018) and three surveys (2011, 2014, and 2018) of survey. Cooking fuel was divided into clean and solid fuel. Cox proportional hazards models were used to estimate the mortality hazard ratio (HR). Subgroup analyses were performed to assess the potential interaction effect. Results: Among the participants in the 2011-2018 survey, 53% reported using solid fuel. Such group was associated with a 9% increase in mortality risk relative to clean fuel users (HR = 1.09, 95% CI = 1.01-1.18). Among participants in the 2014-2018 survey, 339 reported a switch from solid to clean fuels and they were not at increased mortality risk relative to the 488 people that reported a stable use of clean fuels (HR = 1.14, 95% CI = 0.99-1.31) although the estimated HR was similar to the one for stable solid fuel users (HR = 1.19, 95%CI = 1.04-1.36 n = 509). Interaction and stratified analyses showed that solid fuel use had an impact on mortality in participants who were non-current smokers, had low dietary diversity scores, and were living in areas with high PM2.5 concentrations (>50 μg/m3) and city population below 8 million (P for interaction < 0.05). The association was robust in the three sensitivity analyses. Conclusion: The finding showed a clear association between solid fuel use and mortality among older Chinese, and an even stronger association between risk of mortality and solid fuel use among individuals exposed to high levels of PM2.5.

Indoor unclean fuel cessation linked with adult cognitive performance in China

Both indoor unclean fuel use and CVD associates with cognitive function. Indoor fuel has transitioned from the use of unclean fuel to clean fuel in recent years in China. The aim of this study was to evaluate the association between adult cognitive function and such a transition and to investigate the potential role of CVD in this association. 7112 participants (26- to 98-years of age) with 12,676 observations living in twelve provinces of China from 1997 to 2015 were extracted based on having complete data. The associations, combined effects, and further mediation effects between indoor unclean fuel use and its transition, CVD, and cognitive function were tested using regression models, stratified analyses, the relative excess risk due to interaction (RERI), mediation analysis methods, and sensitivity analyses. Between 1997 and 2015, cooking fuel use coal and wood went down a lot in China, from a baseline of 26.9% to 6.1%, from 30.1% to 11.5%, respectively. Such a transition showed a positive association with delayed verbal recall (B = 0.288, p < 0.01), especially in rural area, subjects with age ≥ 65 years old, and women (all P < 0.05). The combined effect of the presence of hypertension during a baseline visit and such a transition on changes in delayed verbal recall was antagonistic (RERI = -0.529, p < 0.05). Moreover, the development of hypertension explained more than 50% of such a fuel transition-related decline of verbal memory. The transition of household energy to clean fuel was associated with a higher adult cognitive function. The presence or the development of CVD appeared to affect the association between indoor air pollution and cognitive function, which suggests a need to further optimize prevention of concurrent CVD and risk factor control in adults at higher risk for cognitive impairment and with indoor unclean cooking fuel, especially in potentially susceptible subgroups.

Reference Values for Five-Repetition Chair Stand Test Among Middle-Aged and Elderly Community-Dwelling Chinese Adults

Background: Previous studies on the five-repetition chair stand test (CS-5) are limited by the representativeness of the sample or the lack of reference equations for CS-5. Defined reference values for CS-5 in a large population are not available for middle-aged and elderly Chinese adults.

Objective: We established age- and sex-stratified reference values for CS-5 times in a large population in China, and to investigate the associations between demographic and anthropometric factors and CS-5 times.

Methods: Analysis of data from the national baseline survey of the China Health and Retirement Longitudinal Study, a nationally representative longitudinal survey that includes 450 urban communities and rural villages within 28 provinces, municipalities, and autonomous regions of China.

Results: Twelve thousand six hundred five of seventeen thousand seven hundred eight participants were included for the reference value analyses. Twelve thousand three hundred out of seventeen thousand seven hundred eight participants were included for the risk factor analyses. Of 12,605 participants, the mean CS-5 time was 10.13 s (SD, 3.32) in men and 11.03 s (SD, 3.54) in women aged 40+ year. The CS-5 times were shorter in men than women of all age categories (P < 0.001). The cut-off points ranged from 5.36 to 9.98 s and from 6.48 to 10.29 s in men and women, respectively. Mean velocity was higher in men than in women (P < 0.001). Age, waist circumference, living in a rural village, and having chronic diseases were positively associated with CS-5 time, whereas male, handgrip strength, currently married, income, and current or ex-drinker were negatively associated with CS-5 time in this population (all P < 0.001).

Conclusions: The comprehensive normative values for CS-5 are essential for enabling clinicians to better evaluate functional performance, determine the appropriate interventional strategy, and promote healthy aging of older adults.

Association between biomass fuel use and the risk of cognitive impairment among older populations in China: a population-based cohort study

BACKGROUND

Cohort studies on the impact of biomass fuel use for cooking on cognitive impairment among older population are still lacking in China and elsewhere. The aim of this study was to examine whether biomass fuel use for cooking is associated with cognitive impairment in Chinese adults aged 65 years or older.

METHODS

The prospective population-based cohort study of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) included participants aged 65 years or older in 2014 who were followed-up until 2018 in 23 provinces in China. The Mini-Mental State Examination (MMSE) was used to assess cognitive function, and cognitive impairment was defined as total MMSE scores less than 18. The association between biomass fuel use and cognitive impairment was evaluated using the Cox proportional hazards model.

RESULTS

Of the 4145 participants included at baseline, participants who reported that they used biomass fuel for cooking (40.43%; IR: 3.11 versus 2.77 per 100 person-years; aHR: 1.27, 95% CI: 1.02-1.58) had a higher risk of cognitive impairment compared with participants who used clean fuels (53.75%). A stratified analyses showed greater effect estimates of cognitive impairment in the older people that lived in the rural areas (aHR: 1.444, 95% CI: 1.08-3.90) and never smoked (aHR: 1.33, 95% CI: 1.04-1.71).

CONCLUSIONS

These findings demonstrated that biomass fuel used for cooking was associated with cognitive impairment, as defined by MMSE, in a population-based study of elderly in China. To prevent cognitive impairment, the structure of cooking fuels requires improvements.