Association between older age and more successful aging: critical role of resilience and depression

Abstract

Objective: There is growing public health interest in understanding and promoting successful aging. While there has been some exciting empirical work on objective measures of physical health, relatively little published research combines physical, cognitive, and psychological assessments in large, randomly selected, community-based samples to assess self-rated successful aging.

Method: In the Successful AGing Evaluation (SAGE) study, the authors used a structured multicohort design to assess successful aging in 1,006 community-dwelling adults in San Diego County, ages 50-99 years, with oversampling of people over 80. A modified version of random-digit dialing was used to recruit subjects. Evaluations included a 25-minute telephone interview followed by a comprehensive mail-in survey of physical, cognitive, and psychological domains, including positive psychological traits and self-rated successful aging, scaled from 1 (lowest) to 10 (highest).

Results: The mean age of the respondents was 77.3 years. Their mean self-rating of successful aging was 8.2, and older age was associated with a higher rating, despite worsening physical and cognitive functioning. The best multiple regression model achieved, using all the potential correlates, accounted for 30% of the variance in the score for self-rated successful aging and included resilience, depression, physical functioning, and age (entering the regression model in that order).

Conclusions: Resilience and depression had significant associations with self-rated successful aging, with effects comparable in size to that for physical health. While no causality can be inferred from cross-sectional data, increasing resilience and reducing depression might have effects on successful aging as strong as that of reducing physical disability, suggesting an important role for psychiatry in promoting successful aging.

Figure 1. Enrollment of participants in the SAGE study

^a No answer, answering machine on repeated calls, etc. ^b Disconnected number, didn’t speak English, deceased, hard of hearing, etc.

Figure 2. Estimated Self- Rated Successful Aging (SRSA) Scores by Pairs of Correlates

Descriptions of Functional Groupings of Key Variables [Table: see text] Note: Physical functioning and resilience are categorized into tertiles. However, depression and cognition could not be well represented by tertiles because a majority of the subjects had no clinically significant depressive symptoms or cognitive impairment. We custom-trichotomized groups for the PHQ-9, based on previously used interpretive cut-scores for severity of depressive symptoms (20): scores of 0–4 = no or minimal depression, 5–9 = mild, and > 10 = moderate to severe depression) and for TICS-m scores (16); 32–48 = no cognitive impairment; 27–31 = mild cognitive impairment; 13–26 = Moderate or greater impairment). Qualitative descriptions of individuals in the top and bottom functioning groups for each variable: SF-36 Physical: Participants in the top tertile (high functioning group) had physical activity limitations “none of the time” or “a little of the time” in all domains. In contrast, those in the bottom tertile (low functioning group) had some limitations in one or more domains of general health, physical functioning, bodily pain, role limitations due to physical problems, energy/vitality, and social functioning. Resilience: Individuals in the top tertile (high functioning group) responded with “often true” or “true nearly all of the time” on virtually all the items. Whereas those in the bottom tertile (low functioning group) responded with “not true at all” or “rarely true” on a majority of the items related to their ability to adapt and persevere in the face of hardship. Examples of the questions include: “I am able to adapt to change” and “I believe I can achieve my goals.” Depression (PHQ-9): Participants in the top (high functioning) group had no to minimal depressive symptoms, whereas most of those in the bottom (low functioning) group suggested moderate to severe depressive symptoms. Individuals in the low functioning group had difficulty sleeping and low energy for more than half the days during the previous two weeks. Many, but not all, of the subjects in the latter group also indicated loss of interest, depressed mood, poor appetite, and low sense of self-worth. Cognition (TICS-m): Subjects in the top (high functioning) group had no cognitive impairment except for 10-word immediate and delayed recall. In contrast, those in the bottom (low functioning) group had impairment on 10-word immediate and delayed recall as well as on tasks related to attention/working memory (serial 7 subtractions). However, individuals in the low functioning group were unimpaired on orientation and execution of simple motor commands.