臺灣失智症的流行病學

Epidemiology of dementia in Taiwan

由於台灣老年人口的快速增加，盛行於老年人的失智症人數也隨之增加。最近的研究顯示，台灣失智症的盛行率，在65歲以上老人約為2-4%，遠低於已開發國家。可能的原因有老年人口結構以較低齡（65-75歲）之老人為主；失智老人死亡率較高；診斷較不容易而被低估；及族群的特性，例如台灣人有脂蛋白E4基因（APO E4）之頻率較低。至於失智症之類型在社區中，以阿爾滋海默氏病（Alzheimer’s disease，AD）為主，約佔半數；其次為血管型失智症（Vascular dementia，VaD約20~25%）及混合型失智症（約5-10%）。發生率之研究顯示台灣65歲以上老人，每年每千人約有13人會變成失智老人。新發生的失智病人，仍以AD居多，約佔40%；VaD者雖仍居次，但比率提高為35%；混合性的比率也佔了15%。由於VaD與混合型失智症之死亡率明顯高於AD，所以在盛行率調查中前兩者之比率相對較低。AD之危險因子有年齡增加、女性、低教育程度（不識字）、具脂蛋白E4基因、及曾嚴重頭部外傷病史。VaD之危險因子則是腦中風、高血壓。社區研究顯示，仍有相當多失智症病人的家屬，因不明暸失智症而未將病人帶到醫院診治。目前各種失智症都逐漸發展出特異性的治療方式，早期診斷變得更有必要。因此對社會大眾作有關失智病之教育，應是值得努力的工作。

Owing to the rapidly increased population of the aged people in Taiwan, the dementia patients who are prevalent in aged people also increase rapidly. The prevalence of dementia among the elderly(aged 65 and over) is around 2-4% in Taiwan, which is lower than those in developed countries. The reason for this low prevalence may result from relatively young elderly people in Taiwan compared to those of developed countries; high mortality among the demented patients; under-estimation due to the difficulty in diagnosis; and ethnic difference, such as low frequency of apolipoprotein E4 among Taiwanese. In prevalence, Alzheimer’s disease(AD) is the leading cause of dementia, and account for about 50%, followed by Vascular dementia(VaD) (20-25%), and mixed AD and VaD(MIX)(5-10%). The incidence of dementia among the elderly in Taiwan is around 13 per thousand person-years(PTPY). The most common cause of new incident dementia cases is AD(around 40-50%), followed by VaD (30-35%), and MIX(15%). The relative increase of VaD and MIX in incidence compared to that in prevalence may result from very high mortality among VaD and MIX. Overall, the 2-year mortality rate was high among the demented(48% in total dementia, 38% in AD, 60% in VaD, and 70% in MIX). The risk factors for AD were increased age, female sex, low education(illiteracy), apolipoprotein E4, and history of major head injury. The risk factors for VaD were stroke and hypertension. The community survey showed that many families of dementia patients were not yet prepared to understand dementia, and therefore did not bring the patients to seek for medical management. As various types of dementia render specific treatment, early and differential diagnosis becomes more and more important. The campaign for public education in dementia deserves more effort.