High-level activities of daily living and disease-specific mortality during a 12-year follow-up of an octogenarian population

Background: Little is known about the relationship between disease-specific mortality and high-level activities of daily living in the elderly. We examined whether mortality is associated with high-level activities of daily living in an octogenarian population. Methods: We conducted a population-based cross-sectional and prospective cohort study in 693 older persons aged 80 years and living in Japan's Fukuoka Prefecture. We then evaluated the association between 12-year disease-specific mortality and high-level functional capacity as measured by the Tokyo Metropolitan Institute of Gerontology Index of Competence, which is a standardized multidimensional 13-item instrument; items 1 through 5 are classified as instrumental self-maintenance activity, items 6 through 9 as intellectual activity, items 10 through 13 as social roles activity, and all 13 items together yield total functional capacity. Results: By the 12-year follow-up of the 693 participants, 413 had died, 242 survived, and 38 were unable to be located. Of the 413 who died, 105 died of cardiovascular disease, 73 of respiratory tract disease, 71 of cancer, and 39 of senility. Of the other 125 deaths, 59 were due to other diseases, and the cause of death for 66 participants is not known. The hazard ratio (HR) for all-cause mortality, adjusted for confounding factors with multivariate Cox analyses, fell by 6% (HR 0.937, 95% confidence interval [CI] 0.899-0.978, P = 0.003) with each one-point increase in participants' scores on the Tokyo Metropolitan Institute of Gerontology Index of total functional capacity. With one-point increases in instrumental self-maintenance activity and in intellectual activity, the HRs for all-cause mortality decreased by 14% (HR 0.856, 95% CI 0.787-0.930, P = 0.000) and 12% (HR 0.884, 95% CI 0.794-0.983, P = 0.023), respectively. Respiratory mortality with HR adjustment fell by 11% (HR 0.887, 95% CI 0.804-0.978, P = 0.016) and 24% (HR 0.760, 95% CI 0.627-0.922, P = 0.005) with one-point increases in the scores of total functional capacity and instrumental self-maintenance activity, respectively. Similarly, mortality due to senility fell by 16% (HR 0.838, 95% CI 0.743-0.946, P = 0.004), 29% (HR 0.707, 95% CI 0.564-0.886, P = 0.003), and 29% (HR 0.710, 95% CI 0.522-0.966, P = 0.029) with one-point increases in the scores of total functional capacity, instrumental self-maintenance activity, and intellectual activity, respectively. Conclusion: These findings suggest that high-level activities of daily living may be an independent predictor of mortality due to all causes, respiratory disease and senility in older persons.