Objective: To investigate the incidence of senile dementia and depression in the elderly and the factors correlative with these disorders.
Methods: All the non-case subjects investigated in a survey of prevalence of senile dementia and depression conducted among the elderly population in Xicheng District, Beijing in 1997 were followed up in 1999. The investigation procedure, instruments and diagnostic criteria were identical with those used in 1997 survey.
Results: The annual incidence rates of senile dementia was 0.89% in those aged 60 and over. The incidence rate of old males and that of the old females were not significantly different. The annual incidence rate of senile dementia in groups aged 60 approximately 64, 64 approximately 69, 70 approximately 74 75 approximately 79 80 approximately 84 85 approximately 89, and 90 and over were 0.15% 0.68 % 0.44% 1.32% 2.41% 5.72% and 5.13% respectively. The incidence rate in the elderly over 90 was lower than that in the group aged 85 approximately 89. The minimum annual incidence rate of depression in the elderly aged 60 and over was 1.28%. The incidence rate of depression was higher in the group with poorer health than in the group with better health. The incidence rates of moderate and severe dementia were not significantly different from those in 1989.
Conclusion: The incidence rate of senile dementia in the elderly remains rather stable during this period of 10 years in Beijing city. The incidence rate of senile dementia is closely correlated with age. The incidence rate of depression in the elderly is remarkably correlated with health status. Senile dementia and depression may coexist in the same person.