Các quốc gia trên toàn thế giới được báo cáo tăng cuộc sống kéo dài và tỷ lệ sinh thấp hơn. Những thay đổi này sociodemographic kết quả ở người cao tuổi, đặc biệt là lâu đời nhất, bao gồm một phân khúc ngày càng tăng của dân số (1). Do đó, chứng mất trí được dự báo là một trong những vấn đề chăm sóc sức khỏe | 17 Understanding Incidence and Prevalence Rates in Mixed Dementia John Gunstad and Jeffrey Browndyke 1. INTRODUCTION Countries throughout the world are reporting increased life-spans and lower birth rates. These sociodemographic changes result in the elderly particularly the oldest old comprising an increasingly larger segment of the population 1 . Consequently dementia is projected to be one of the major health-care problems of future decades 2 . Alzheimer s disease AD and vascular dementia VaD have long been considered the most prevalent forms of dementia 3 . More recently increased attention has been given to the co-occurrence of AD and VaD typically referred to as mixed dementia MD . Although first described in the 1960s MD has received relatively little attention until recently 4 . It has been speculated that MD may be the most common form of dementia 5 but its true prevalence remains unknown. A growing number of studies report the frequency of MD within their samples of patients with dementia or in the community at large but these studies were designed to detect AD or VaD not MD. The goals of this chapter are to present the incidence prevalence rates of MD reported in past studies to identify possible methodological concerns of these studies and to suggest future directions for MD studies. To accomplish these goals this chapter has been divided into five sections 2. RATES OF MIXED DEMENTIA . Terminology Review The prevalence of a disorder may be defined as the fraction proportion of a group possessing a clinical outcome at a given point in time and is measured by a single examination or survey of a group 6 . Incidence rates refer to the fraction or proportion of a group initially free of the outcome which develops the outcome over a given period of time 6 . To put these definitions into more concrete terms incidence rates refer to the number of examined persons that develop MD within a particular time period whereas prevalence rates refer to the number of
