Association of Long-term Exposure to Ambient Air Pollution With Cognitive Decline and Alzheimer's Disease-Related Amyloidosis.

BACKGROUND: Air pollution induces neurotoxic reactions and may exert adverse effects on cognitive health. We aimed to investigate whether air pollutants accelerate cognitive decline and affect neurobiological signatures of Alzheimer's disease (AD). METHODS: We used a population-based cohort from the Chinese Longitudinal Healthy Longevity Survey with 31,573 participants and a 10-year follow-up (5878 cognitively unimpaired individuals in Chinese Longitudinal Healthy Longevity Survey followed for 5.95 ± 2.87 years), and biomarker-based data from the Chinese Alzheimer's Biomarker and Lifestyle study including 1131 participants who underwent cerebrospinal fluid measurements of AD-related amyloid-ß (Aß) and tau proteins. Cognitive impairment was determined by education-corrected performance on the China-Modified Mini-Mental State Examination. Annual exposures to fine particulate matter (PM2.5), ground-level ozone (O3), and nitrogen dioxide (NO2) were estimated at areas of residence. Exposures were aggregated as 2-year averages preceding enrollments using Cox proportional hazards or linear models. RESULTS: Long-term exposure to PM2.5 (per 20 µg/m3) increased the risk of cognitive impairment (hazard ratio, 1.100; 95% CI: 1.026-1.180), and similar associations were observed from separate cross-sectional analyses. Exposures to O3 and NO2 yielded elevated risk but with nonsignificant estimates. Individuals exposed to high PM2.5 manifested increased amyloid burdens as reflected by cerebrospinal fluid-AD biomarkers. Moreover, PM2.5 exposure-associated decline in global cognition was partly explained by amyloid pathology as measured by cerebrospinal fluid-Aß42/Aß40, P-tau/Aß42, and T-tau/Aß42, with mediation proportions ranging from 16.95% to 21.64%. CONCLUSIONS: Long-term exposure to PM2.5 contributed to the development of cognitive decline, which may be partly explained by brain amyloid accumulation indicative of increased AD risk.

Association between allostatic load and mortality among Chinese older adults: the Chinese Longitudinal Health and Longevity Study.

BACKGROUND: Allostatic load (AL) has shown that high burden of AL is associated with increased risk of adverse outcomes, but little attention has been paid to China with largest ageing population in the world. OBJECTIVE: This study is to examine the association between AL and all-cause mortality among Chinese adults aged at least 60 years. DESIGN: Population-based prospective cohort study. SETTING: In 2011-2012, an ancillary study, in which a blood test was added, including a total of 2439 participants, was conducted in eight longevity areas in the Chinese Longitudinal Healthy Longevity Survey. PARTICIPANTS: The final analytical sample consisted of 1519 participants (mean±SD age: men 80.5±11.3 years; women 90.2±11.8 years and 53% women). PRIMARY OUTCOME MEASURE: Cox models were used to examine the association between AL and mortality among men and women, separately. Analyses were also adjusted for potential confounders including age, ethnicity, education and marital status, smoking and exercise. RESULTS: Male with a medium AL burden (score: 2-4) and high AL burden (score: 5-9) had a 33% and 118% higher hazard of death, respectively, than those with a low AL burden (score: 0-1). We did not find significant difference between females with different levels of AL burden. CONCLUSION: Higher AL burden was associated with increased all-cause mortality among Chinese men aged at least 60 years. However, we did not find strong association among women. In conclusion, Intervention programmes targeting modifiable components of the AL burden may help prolong lifespan for older adults, especially men, in China.

Number of natural teeth, denture use and mortality in Chinese elderly: a population-based prospective cohort study.

BACKGROUND: The associations between the number of natural teeth/denture use and all-cause mortality remain unclear due to lake of investigation for the potential interaction between tooth loss and denture use and for the potential changes in these exposures over time in older adults. We undertake this study to evaluate the associations of the number of natural teeth and/or denture use with mortality in Chinese elderly. METHODS: This is a prospective cohort study of 36,283 older adults (median age: 90). The number of natural teeth and denture use were collected with structured questionnaire. We evaluated hazard ratios (HRs) and confidence intervals (CIs) using a Cox proportional hazards model adjusting for demographic factors, education, income, lifestyle factors, and comorbidities. RESULTS: We documented 25,857 deaths during 145,947 person-years of observation. Compared to those with 20+ teeth, tooth loss was associated with a gradual increase in mortality, with an adjusted HR of 1.14 (95% CI, 1.06 to 1.23) for those with 10-19 teeth, 1.23 (95% CI, 1.15 to 1.31) for those with 1-9 teeth, and 1.35 (95% CI, 1.26 to 1.44) for those without natural teeth. Denture use was associated with lower risk of mortality (adjusted HR 0.81; 95% CI, 0.77 to 0.84). Subgroup analyses indicated that the benefit of denture use was greater in men than in women (P = 0.02) and tended to decrease with age (P < 0.001). The effects of denture use did not differ among various degrees of tooth loss (P = 0.17). CONCLUSIONS: Tooth loss was associated with an increased risk of mortality in older adults. Denture use provided a protective effect against death for all degrees of tooth loss however, this effect appeared to be modified by sex and age.

Association Between Late-Life Blood Pressure and the Incidence of Cognitive Impairment: A Community-Based Prospective Cohort Study.

OBJECTIVES: To investigate the association between late-life blood pressure and the incidence of cognitive impairment in older adults. DESIGN: Prospective cohort study. SETTING: Community-living older adults from 22 provinces in China. PARTICIPANTS: We included 12,281 cognitively normal [Mini-Mental State Examination (MMSE) ≥ 24] older adults (median age: 81 years) from the Chinese Longitudinal Healthy Longevity Survey. Eligible participants must have baseline blood pressure data and have 1 or more follow-up cognitive assessments. MEASUREMENTS: Baseline systolic (SBP) and diastolic blood pressure (DBP) were measured by trained internists. Cognitive function was evaluated by MMSE. We considered mild/moderate/severe cognitive impairment (MMSE <24, and MMSE decline ≥3) as the primary outcome. RESULTS: The participants with hypertension had a significantly higher risk of mild/moderate/severe cognitive impairment (hazard ratio [HR] 1.17, 95% confidence interval [CI] 1.10-1.24). Overall, the associations with cognitive impairment seem to be hockey stick-shaped for SBP and linear for DBP, though the estimated effects for low SBP/DBP were less precise. High SBP was associated with a gradual increase in the risk of mild/moderate/severe cognitive impairment (P trend < .001). Compared with SBP 120 to 129 mmHg, the adjusted HR was 1.17 (95% CI 1.07-1.29) for SBP 130 to 139 mmHg, increased to 1.54 (95% CI 1.35-1.75) for SBP ≥180 mmHg. Analyses for high DBP showed the same increasing pattern, with an adjusted HR of 1.09 (95% CI 1.01-1.18) for DBP 90 to 99 mmHg and 1.19 (95% CI 1.02-1.38) for DBP ≥110 mmHg, as compared with DBP 70 to 79 mmHg. CONCLUSION: Late-life high blood pressure was independently associated with cognitive impairment in cognitively normal Chinese older adults. Prevention and management of high blood pressure may have substantial benefits for cognition among older adults in view of the high prevalence of hypertension in this rapidly growing population.

Revisiting the association of blood pressure with mortality in oldest old people in China: community based, longitudinal prospective study.

OBJECTIVE: To examine the associations of blood pressure with all cause mortality and cause specific mortality at three years among oldest old people in China. DESIGN: Community based, longitudinal prospective study. SETTING: 2011 and 2014 waves of the Chinese Longitudinal Healthy Longevity Survey, conducted in 22 Chinese provinces. PARTICIPANTS: 4658 oldest old individuals (mean age 92.1 years). MAIN OUTCOME MEASURES: All cause mortality and cause specific mortality assessed at three year follow-up. RESULTS: 1997 deaths were recorded at three year follow-up. U shaped associations of mortality with systolic blood pressure, mean arterial pressure, and pulse pressure were identified; values of 143.5 mm Hg, 101 mm Hg, and 66 mm Hg conferred the minimum mortality risk, respectively. After adjustment for covariates, the U shaped association remained only for systolic blood pressure (minimum mortality risk at 129 mm Hg). Compared with a systolic blood pressure value of 129 mm Hg, risk of all cause mortality decreased for values lower than 107 mm Hg (from 1.47 (95% confidence interval 1.01 to 2.17) to 1.08 (1.01 to 1.17)), and increased for values greater than 154 mm Hg (from 1.08 (1.01 to 1.17) to 1.27 (1.02 to 1.58)). In the cause specific analysis, compared with a middle range of systolic blood pressure (107-154 mm Hg), higher values (>154 mm Hg) were associated with a higher risk of cardiovascular mortality (adjusted hazard ratio 1.51 (95% confidence interval 1.12 to 2.02)); lower values (<107 mm Hg) were associated with a higher risk of non-cardiovascular mortality (1.58 (1.26 to 1.98)). The U shaped associations remained in sensitivity and subgroup analyses. CONCLUSIONS: This study indicates a U shaped association between systolic blood pressure and all cause mortality at three years among oldest old people in China. This association could be explained by the finding that higher systolic blood pressure predicted a higher risk of death from cardiovascular disease, and that lower systolic blood pressure predicted a higher risk of death from non-cardiovascular causes. These results emphasise the importance of revisiting blood pressure management or establishing specific guidelines for management among oldest old individuals.

Associations of Body Mass Index and Waist Circumference with 3-Year All-Cause Mortality Among the Oldest Old: Evidence from a Chinese Community-Based Prospective Cohort Study.

OBJECTIVE: Current international and national guidelines for body mass index (BMI) and waist circumference (WC) have been recommended to all adults. However, whether recommendations applied to the oldest old (aged 80+) is poorly known. The study objective was to investigate the relation of BMI and WC with 3-year all-cause mortality among the oldest old. DESIGN, SETTING, AND PARTICIPANTS: A total of 4361 Chinese oldest old (mean age 91.8) participated in this community-based prospective cohort study. MEASUREMENTS: BMI and WC were measured at baseline in 2011 and were used as continuous variables and as categorized variables by recommendations or by tertiles. Adjusted, sex-stratified Cox models with penalized splines and Cox models were constructed to explore the association. RESULTS: Greater BMI and WC were linearly associated with lower mortality risk in both genders. The mortality risk was the lowest in overweight or obese participants (BMI ≥ 24.0) and was lower in participants with abdominal obesity. Compared to the upper tertile, those in the middle and lower tertile of BMI had a higher risk of mortality for men [hazard ratio (HR): 1.23 (1.02-1.48) and 1.53 (1.28-1.82)] and for women [HR: 1.21 (1.03-1.41) and 1.35 (1.15-1.58)]; it was also found in participants in the middle and lower tertile of WC for men [HR: 1.21 (1.01-1.46) and 1.41 (1.18-1.69)] and for women [HR: 1.35 (1.15-1.58) and 1.55 (1.32-1.81)] (all the P values for trend <.001). These findings were robust in further sensitivity analyses or when using propensity score matching, in subgroup analyses, or in octogenarians, nonagenarians, and centenarians. CONCLUSIONS: In Chinese oldest old, both higher BMI and higher WC predict better survival in both genders. The finding suggests optimal BMI and WC may be sensitive to age, thus, the current recommendations for the oldest old may need to be revisited.

Association of Body Mass Index With Disability in Activities of Daily Living Among Chinese Adults 80 Years of Age or Older.

Importance: Body mass index (BMI) shows a U-shaped association with impaired physical functioning among adults; the association is reduced or eliminated with aging. Objective: To examine whether BMI is associated with subsequent disability in activities of daily living (ADL) in Chinese adults age 80 years or older. Design, Setting, and Participants: Data were obtained on 16 022 adults age 80 years or older who were able to perform ADL independently at baseline from the Chinese Longitudinal Healthy Longevity Study, a community-based prospective cohort study conducted in 23 provinces of China. The study was initiated in 1998, with follow-up and recruitment of new participants in 2000, 2002, 2005, 2008, 2011, and 2014. Main Outcomes and Measures: Disability in ADL was defined as dependence in eating, toileting, bathing, dressing, indoor activities, and/or continence. Results: Among the 16 022 participants, 45.2% were men and 54.8% were women, with a mean (SD) age of 92.2 (7.2) years and a mean (SD) BMI (calculated as weight in kilograms divided by height in meters squared) of 19.3 (3.8). During 70 606 person-years of follow-up, 8113 participants with disability in ADL were identified. Cox proportional hazards regression models with penalized splines showed that BMI was linearly associated with disability in ADL: each 1-kg/m2 increase in BMI corresponded to a 4.5% decrease in the risk of disability in ADL. In comparison with individuals in the fourth quintile for BMI, the adjusted hazard ratio for disability in ADL was 1.38 (95% CI, 1.29-1.48) in the first quintile, 1.37 (95% CI, 1.28-1.47) in the second quintile, 1.11 (95% CI, 1.04-1.19) in the third quintile, and 0.85 (95% CI, 0.79-0.91) in the fifth quintile (P < .001 for trend). When BMI was categorized by Chinese guidelines, the underweight group (BMI <18.5) showed significantly increased risk of disability in ADL (hazard ratio, 1.34; 95% CI, 1.28-1.41) and the overweight or obese group (BMI ≥24.0) showed significantly decreased risk of disability in ADL (hazard ratio, 0.84; 95% CI, 0.78-0.91) compared with the normal weight group (BMI 18.5 to <24.0) (P < .001 for trend). Conclusions and Relevance: Higher BMI was associated with a lower risk of disability in ADL among Chinese adults age 80 years or older, which suggests that current recommendations for BMI may need to be revisited. More attention should be paid on underweight, rather than overweight or obesity, for the prevention of disability in ADL after age 80 years.