Modifiable factors for the length of life with disability before death: Mortality retrospective study in Japan

Background: Past studies have measured and described the length of life with disability before death, but there has been no study of the relationship between modifiable lifestyle factors and duration of disability. Objective: To examine whether there are modifiable factors influencing the length of life with disability before death. Methods: The study was designed as a retrospective observation of the deceased who had earlier been enrolled in a prospective cohort study. During the followup period (1996-1999), we documented 781 deaths among those who were 70-79 years of age at the base-line survey in 1994 (n = 10,216). In 2000, we interviewed family members of the deceased about the duration of the subjects' disability before death (n = 655). Results: The median duration of disability before death was approximately 6 months. Both higher Body Mass Index (BMI) and shorter time spent walking were significantly associated with an increased risk of long-term disability (more than 6 months). The odds ratios of long-term disability were 1.3 in those with BMI 20-25 and 2.1 in those with BMI >25, compared with BMI <20. The odds ratios of long-term disability were 1.3 in those walking for 0.5-0.9 h/day and 1.7 in those walking for <0.5 h/day, compared with those walking for >1.0 h/day. These relationships were unchanged after stratification for causes of death. Conclusion: Weight control and walking in later life may shorten the length of life with disability before death.