Relation between intellectual dysfunctioning and mortality in community-residing older people.

ABSTRACT

OBJECTIVE: To examine the relationship between intellectual dysfunctioning and mortality in a community-residing older population. DESIGN: Of the 1473 randomly selected people aged 65 years and older living in Settsu, Osaka Prefecture, in October 1992, 1405 were contacted. Data for assessment of intellectual dysfunctioning were obtained from 1383 people (98.4%), who constituted the study cohort. Follow-up for 42 months was completed for 1300 subjects (94.0%; 1117 living, 183 deceased). MEASURES: Data on general health status, history of health management, psychosocial conditions, and intellectual dysfunctioning were collected by means of interviews during home visits at the time of enrollment. Intellectual dysfunctioning was determined with the assessment instrument developed by the Social Survey Division of the Office of Population Censuses (OPCS) in Great Britain. RESULTS: The Kaplan-Meier analysis indicated that the estimated survival rates for men and women decreased with a decline in intellectual function in two age groups 65 to 74 and 75 years and older. For both sexes, the log rank test showed that the curves among the four groups based on intellectual dysfunctioning (intact, mild, moderate, and severe) achieved statistical significance for the age group of 75 years and older. For both age groups and each of the levels of intellectual dysfunctioning, the estimated survival rate for men was lower than that for women. Application of the Cox proportional hazards model resulted in unadjusted hazard ratios of mild, moderate, and severe intellectual dysfunctioning for mortality of 1.68, 2.44, and 5.37, respectively. Multivariate analysis on the other hand, yielded adjusted hazard ratios of mild, moderate, and severe intellectual dysfunctioning of 1.19, 1.12, and 1.74, respectively, leaving severe dysfunctioning as the only statistically significant factor associated with mortality. Other factors such as sex, age, general health status, history of management, and psychosocial conditions were controlled. CONCLUSION: Intellectual dysfunctioning, as measured by an assessment instrument developed by OPCS, represents an increased risk factor for mortality among community-residing older people.