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.

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.