Epidemiology of Alzheimer's disease in Wales

Abstract

BackgroundThere is a rapidly progressive increase in the ageing population around the world, especially in developed countries such as the UK, Japan, and Germany. Dementia is the third leading cause of death in the USA, on a par with cerebrovascular diseases. Alzheimer's disease is the most common cause of dementia, accounting for more than 60% of cases. There have been several studies on the incidence of dementia; however, many have been based at single sites or only within a suburb of cities. Studies on the incidence of Alzheimer's disease are even more limited. I aimed to study the epidemiology of Alzheimer's disease in individuals aged 60 years and older in Wales and the relation between Alzheimer's disease and age. MethodsI used the Patient Episode Database for Wales to identify patients who were diagnosed with Alzheimer's disease between 1999 and 2010. This database contains all inpatient and day case activity undertaken in NHS Wales in addition to data for Welsh residents treated in English Trusts. The data are gathered and coded at each hospital. The records are then electronically transferred to the NHS Wales Informatics Service, where they are validated and merged into the main database. There are about 100 000 episodes of care processed per month. The cases of Alzheimer's disease were extracted from the database using the International Classification of Diseases (version 10) diagnosis codes G300, G301, G308, G309. The incidence of Alzheimer's disease was calculated using the mid-year population estimates of Wales for each year of the study. The rates are expressed per 1000 person-years. A Poisson regression model was fitted to assess temporal trends. Rate ratios and 95% CIs were calculated and compared over the study period. The data were analysed using SPSS version 18.0 and the level of statistical significance at which the null hypothesis was rejected was 0·05. FindingsDuring the 12 years, 14 534 people were diagnosed with Alzheimer's disease in Wales (appendix). The overall prevalence of Alzheimer's disease in individuals 60 years or older was 1·8% and the overall incidence was estimated as 1·5 per 1000 person-years. However, this figure is likely to be a substantial underestimate because only patients who present to doctors are included in the database. The prevalence of Alzheimer's disease in individuals between 60 and 74 years was 0·5%, rising to 4·5% in those aged 75 years and older. The incidence of Alzheimer's disease increased during the study period from 1·4 per 1000 person-years in 1999 to 1·9 per 1000 person-years in 2010 (appendix). InterpretationThe incidence of Alzheimer's disease is progressively increasing in Wales. Prevalence and incidence rates rise with age. Public awareness needs to be enhanced to identify symptoms of Alzheimer's disease earlier, which will enable adequate support to be provided as soon as possible to extend patients' independence and slow the progression of symptoms. FundingNone.