背景：台灣失智症盛行率急遽攀升，隨著老齡化人口增加，失智症不僅對個體和家庭產生深遠影響，也對社會和國家的健康體系帶來沉重負擔。為制定更有效的預防策略，迫切需要深入研究失智症的風險因子。過去研究顯示失智症與發炎感染有密切關聯，多項流行病學研究亦支持流感疫苗接種與降低失智症風險之關聯。因此，本研究旨在探討台灣65歲以上長者接種流感疫苗是否與較低的失智症風險相關。
目的：（一）探討台灣65歲以上年長者接種流感疫苗後是否與較低的失智症風險相關；（二）流感疫苗與失智之相關性是否受到年齡和性別的影響；延伸探討（三）失智症風險是否隨每年接種更多次流感疫苗而降低。
方法：本研究採用回溯性世代追蹤研究法，研究對象取自我國全民健康保險申報資料之2010年200萬人承保抽樣歸人檔，以2005至2010年滿65歲以上之長者為研究世代，並以這段期間有接種流感疫苗者作為暴露組。追蹤期間從2011至2018年，使用Cox比例風險模型計算接種和未接種流感疫苗之65歲以上長者的失智風險。競爭風險模型用於控制由於死亡導致無法觀測失智事件發生的誤差。最後，使用分層分析評估流感疫苗接種對年齡和性別的影響。
結果：（一）研究世代為125,855名65歲以上長者，其中93,970名接受流感疫苗接種。接種與未接種流感疫苗的長者在多項因素上存在顯著差異，整體而言接種組的失智症發生率約為未接種組的1.2倍。（二）分析年齡及性別分層後，風險差異存在，但在考慮潛在干擾因素後，相關性較低。另外，針對阿茲海默症、血管性失智症及其他失智症進行單獨觀察，各別失智症的發生率也是稍高於未接種疫苗組的長者。（三）對流感疫苗接種次數的探討顯示，接種6次以上的長者風險較高，但在校正後相關性有限。總體而言，本研究強調了潛在干擾因素對研究結果的調整重要性。
結論：根據全民健康保險資料庫的世代追蹤研究，本研究發現65歲以上長者中，流感疫苗接種組整體失智症發生率稍高，但經校正後相關性下降，顯示接種與失智風險相對較低。年齡、性別及接種次數的分層分析呈現些微差異，但經校正後相關性受限。與先前文獻略有不同，可能源於樣本特性、資料來源限制及未全面考慮的潛在干擾因素。總體而言，未來研究需更全面考慮多方面因素，以深入理解流感疫苗接種與失智風險的因果關係。

While several studies have explored the association between influenza vaccine and dementia in the past, the current findings are challenging to generalize to the overall elderly population in Taiwan. Based on the Taiwan National Health Insurance Database, this study conducted an extensive 8-year follow-up investigation on individuals aged 65 to examine the impact of influenza vaccine administration on the risk of dementia. The results indicated a slightly higher overall incidence of dementia in the influenza vaccine group compared to the non-vaccine group. Further analysis, considering age and gender stratification, revealed higher dementia incidence rates in the influenza vaccine group, with a slight increase in risk associated with more frequent vaccinations. However, after adjusting for confounding factors, the correlation was limited, and the study faced methodological issues. In conclusion, future research should comprehensively consider various factors to gain a deeper understanding of the causal relationship between influenza vaccine administration and dementia risk.

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