Psychosocial Risk Factors for Alzheimer's Disease
He, Y. L., Zhang, X. K., Zhang, M. Y., Hong Kong Journal of Psychiatry
This study aims to explore the relationship between psychosocial factors and risk for Alzheimer's disease and to identify specific psychosocial risk factors from hundreds of potential factors among the Chinese population. A community-based prospective cohort study of dementia in the elderly population performed in Shanghai enrolled 6634 patients older than 55 years from Jing An District by an age-stratified cluster method. Patients were screened by the Mini-Mental State Examination and followed up for 10 years with assessment at 5-yearly intervals. The data reported here identify some psychosocial factors for Alzheimer's disease from 5- and 10-year follow-up studies. 5055, 3024, and 1203 people completed the base line survey and 5- and 10-year follow-up studies, respectively. The psychosocial risk factors found in both follow-up studies were low educational level, low cognitive function, low occupational status, lack of social interaction and leisure activities, and poor well being. Mini-Mental State Examination score and Activities of Daily Living score had a predictive effect on the onset of Alzheimer's disease. The conclusion generated from the study was that psychosocial risk factors did impact on the onset and development of Alzheimer's disease. The emergence of some intervention-susceptible risk factors such as educational level and involvement in leisure activities provides the basis for future intervention study.
Key words: Alzheimer's Disease; Dementia; Elderly; Psychosocial Risk Factor; Relative Risk
Geriatric mental health problems are gradually emerging since the proportion of elderly people among the general population is continually increasing. Dementia, especially Alzheimer's disease (AD), is one of the most common and severe mental health problems to afflict elderly people. A community-based study from Shanghai showed that the prevalence of dementia was approximately 4 to 5% for people aged more than 65 years, with nearly two-thirds of them suffering from AD. (1) Dementia is now the fourth most common cause of death, after coronary heart disease, cerebral vascular disease, and malignant tumour.
Although pathological features of AD were described 100 years ago, the aetiology of AD remains unclear. Therefore, the exploration of risk factors for AD is an important research question.
During the past decade, research for risk factors for AD focused on molecular genetics. (2-6) The amyloid precursor protein (APP) genes of chromosome 21, the presenilin-1 gene of chromosome 14, and the presenilin-2 gene of chromosome 1 have been identified. Mutation or polymorphism of alleles in these genes was associated with the occurrence of AD, especially the early-onset type of familial AD. For sporadic late-onset AD, which accounts for 90% of all AD, it was found that the Apo E4 allele was involved. For example, in Shanghai, gene frequency of Apo E4 was 0.105 among healthy elderly people. (7) The frequency is lower than that for western countries but similar to the frequency in other Asian countries. On the other hand, Apo E4 gene frequency among people with late-onset AD was 0.262, 2.5-fold that of healthy elderly people. This higher relative risk (RR) is similar to reports from both western and Asian countries.
Although biological risk factors for AD have been intensely studied, factors such as family history and Apo E4 do not completely explain the occurrence of AD. No definite or specific biological causes have been found among most sporadic cases. The population attributable risk proportion (PARP) of biological risk factors is not high. However, there are risk factors other than biological factors for AD such as psychosocial considerations. While it is difficult to intervene in most of the biological factors, more attention could be directed to the study of psychosocial risk factors for AD. More than 30 psychosocial risk factors have been found for the onset of dementia. …