Association between Blood Manganese Exposure and Cognitive Impairment in the Elderly Aged 65 Years Older in Eight Longevity Areas of China

Objective To investigate the relationship between the level of blood manganese exposure and the risk of cognitive impairment in the elderly aged 65 years and older in longevity areas in China.

Methods A total of 2 423 elderly people from eight longevity areas were selected from 2017 follow-up survey on health influencing factors of the elderly population in China. A questionnaire survey was conducted to investigate their demographic variables, behavior and lifestyle, and health status. At the same time, mini-mental state examination (MMSE) was used to assess the cognitive function of the respondents. The fasting venous blood was collected, and inductively coupled plasma mass spectrometry was used to determine the blood manganese level. According to the quartiles of blood manganese exposure, the elderly were divided into four groups: Q₁ group (< 8.69 μg/L), Q₂ group (8.69-10.71 μg/L), Q₃ group (10.71-13.39 μg/L), and Q₄ group (≥ 13.39 μg/L). A multivariate logistic regression model was employed to analyze the level of blood manganese exposure and the risk of cognitive impairment in all respondents and elderly people of different ages.

Results A total of 673 (27.78%) elderly people had cognitive impairment. The prevalence rates of cognitive impairment in the Q₁, Q₂, Q₃ and Q₄ groups were 21.9% (132/603), 27.2% (165/607), 31.8% (193/607), and 30.2% (183/606), respectively, with a significant difference among the groups (P < 0.05). The multivariate logistic regression model analysis showed that in all respondents and the elderly aged 100 years and older, the risk of cognitive impairment in Q₃ group was increased compared with the Q₁ group (OR=1.46 and 2.41, 95%CI: 1.04-2.05 and 1.06-5.48); in the elderly aged 65 to 79 years, the risk of cognitive impairment in Q₃ and Q₄ groups was increased compared with the Q₁ group (OR=3.61 and 3.10, 95%CI: 1.22-10.69 and 1.06-9.05).

Conclusion The elderly aged 65 to 79 years and 100 years and older are more vulnerable to high level of blood manganese in the eight longevity areas, which may increase the risk of cognitive impairment.