臺灣社區老年人長期空氣汙染物暴露與認知功能之關聯性研究

Abstract

研究背景：隨著人口老化迅速，認知功能障礙和失智症的罹患率迅速增加。過去的流行病學研究顯示，長期暴露於空氣污染物中會影響認知功能。然而，這些研究主要探討總體認知功能，且研究結果並不一致。因此本研究旨於探討長期暴露於空氣污染物與總體或領域認知功能缺損的關係。 研究方法：本研究為一個前瞻性世代追蹤研究，於基線（2011至2013年）招募605位參加臺大醫院老人健康檢查65歲以上的社區老人，排除有以下情形之受試者：已被診斷為失智症、正在服用治療阿茲海默氏症用藥、中風或頭部受傷、腦部腫瘤≧3公分、蒙特利爾認知評估臺灣版（Taiwanese version of the Montreal Cognitive Assessment, MoCA-T）總分≦21分（疑似失智）、身體活動量≧10,000代謝當量-分鐘/周、無載脂蛋白E e4對偶基因型、居住地址不完整以致於無法定位、居住於臺北基隆大都會區以外的地區、基線前10年間有住址不全或是超過半年居住於國外等狀況、任一項認知功能分數於2013至2015年或是2015至2017年進行世代追蹤時出現遺失值，共計360位長者納入研究分析。認知功能採用MoCA-T和一系列神經心理測試進行評估。三項空氣汙染物資料則取自於行政院環境保護署測站之數據，其中包括粒徑小於等於10微米（μm）之懸浮微粒（particulate matter ≦10 μm in diameter，PM10），粒徑小於等於2.5微米（μm）之細懸浮微粒（particulate matter ≦2.5 μm in diameter，PM2.5），和二氧化氮（nitrate dioxide, NO2）。先將測站資料及受試者地址以貝氏最大熵法之時空分析（Space-Time Analysis Rendering with Bayesian Maximum Entropy, Star-BME）進行時空推估並模擬每位受試者暴露資料，接著以廣義估計方程式探討空氣汙染物暴露與認知功能間隨時間的變化關係並同時調整重要變數。 研究結果：最高濃度的PM2.5暴露（>29.98 μg/ m3）會增加罹患認知功能障礙的風險（MoCA-T<24）〔勝算比（odds ratio，OR）= 5.08，95% 信賴區間（confidence interval，CI）：1.15至22.52〕；最高濃度的PM10暴露（>51.20 μg/ m3）和邏輯記憶、語言流暢度、注意力較差的表現有顯著關聯〔相關係數（β）= -0.40至-0.26〕，中等濃度的PM10暴露（49.57-51.20 μg/m3）和語言流暢度表現較差有關（β= -0.32，95% CI= ¬-0.53至-0.12）。同時暴露於最高濃度的PM10和NO2（>28.62 ppb）與語言流暢度表現較差有關（β= -0.23，95% CI= ¬-0.39至-0.07）。 結論：長期暴露於高濃度空氣污染物，四年後追蹤的認知功能表現越差（PM2.5與總體認知；PM10與邏輯記憶、語言流暢度、注意力）；同時暴露於PM10和NO2則與語言流暢度表現較差相關。環境中空氣汙染物（PM2.5、PM10、NO2）的暴露為失智症的重要危險因子，除了積極改善空氣品質之外，希望未來環境保護署在制定空氣品質標準時，能將失智症納入為空氣汙染造成的不良健康效應。

Background: As the population ages quickly, the prevalences of cognitive impairment and dementia increase rapidly. Prior epidemiological studies have shown that long-term exposure to air pollutants affected cognitive function. However, these studies focused on global cognition and the results have been inconsistent. Therefore, this study aims to examine the association of long-term exposure to air pollutants with global and domain-specific cognitive function. Method: This was a prospective cohort study. A total of 605 community-dwelling elders aged 65 and older were recruited from the elderly health check program of National Taiwan University Hospital at baseline (2011-2013). Participants with the following conditions were excluded: diagnosis of dementia, use medication of Alzheimer’s disease, stroke, head injury, brain tumor ≧ 3cm, the score of Taiwanese version of the Montreal Cognitive Assessment (MoCA-T) of baseline ≦ 21 (suspected dementia), physical activity ≧ 10000 met-min/week, lack of data on APOE e4 status, unable to locate a participant’s address due to incomplete residential address information, living outside of Taipei and Keelung metropolitan area, missing residential address or living abroad over 6 months each year 10 years prior to baseline, lack of cognition data during follow-ups (2013-2015 and 2015-2017). After exclusion, a total of 360 participants were included for statistical analysis. Cognitive function was assessed by MoCA-T and a battery of neuropsychological tests. Level of three air pollutants were collected by monitoring stations of Environmental Protection Agency (EPA), these pollutants included particulate matter ≦ 2.5 μm in diameter (PM2.5), particulate matter ≦ 10 μm in diameter (PM10), and nitrate dioxide (NO2). Space-Time Analysis Rendering with Bayesian Maximum Entropy (Star-BME) was used to estimate the individual exposure to each air pollutant based on participant’s residential address. Generalized Estimating Equations (GEEs) were then used to explore the association of exposure to air pollutants and cognitive function over time adjusting for important covariates. Result: Exposure to the highest tertile of PM2.5 (>29.98 μg/m3) was associated with increased risk of cognitive impairment (MoCA-T <24) (OR= 5.08, 95% CI: 1.15 to 22.52); exposure to the highest tertile of PM10 (>51.20 μg/m3) was associated with poor performance of logical memory, verbal fluency and attention (β= -0.40 to -0.26). Exposure to the medium tertile of PM10 (49.57-51.20 μg/m3) was associated with poor performance of verbal fluency (β= -0.32, 95% CI: -0.53 to -0.12). Simultaneous exposure to the highest tertile of PM10 and NO2 (> 28.62 ppb) was associated with poor performance of verbal fluency (β= -0.23, 95% CI: -0.39 to -0.07). Conclusion: Long-term and high-level exposure to air pollutants were associated with poor performance of cognition over 4-year follow-up (PM2.5 related to MoCA-T <24, PM10 related to poor performance of logical memory, verbal fluency and attention). Simultaneous exposure to PM10 and NO2 was associated with poor performance of verbal fluency. PM2.5, PM10, NO2 are important risk factors of dementia. In addition to actively improving air quality, it is important to include dementia as one of the health outcomes for revising air quality standards.