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. 2008 May 21;3(5):e2232.
doi: 10.1371/journal.pone.0002232.

Social vulnerability, frailty and mortality in elderly people

Melissa K Andrew  1 , Arnold B Mitnitski, Kenneth Rockwood
Affiliations

Social vulnerability, frailty and mortality in elderly people

Melissa K Andrew et al. PLoS One. .

Abstract

Background: Social vulnerability is related to the health of elderly people, but its measurement and relationship to frailty are controversial. The aims of the present study were to operationalize social vulnerability according to a deficit accumulation approach, to compare social vulnerability and frailty, and to study social vulnerability in relation to mortality.

Methods and findings: This is a secondary analysis of community-dwelling elderly people in two cohort studies, the Canadian Study of Health and Aging (CSHA, 1996/7-2001/2; N = 3707) and the National Population Health Survey (NPHS, 1994-2002; N = 2648). Social vulnerability index measures that used self-reported items (23 in NPHS, 40 in CSHA) were constructed. Each measure ranges from 0 (no vulnerability) to 1 (maximum vulnerability). The primary outcome measure was mortality over five (CHSA) or eight (NPHS) years. Associations with age, sex, and frailty (as measured by an analogously constructed frailty index) were also studied. All individuals had some degree of social vulnerability. Women had higher social vulnerability than men, and vulnerability increased with age. Frailty and social vulnerability were moderately correlated. Adjusting for age, sex, and frailty, each additional social 'deficit' was associated with an increased odds of mortality (5 years in CSHA, odds ratio = 1.05, 95% confidence interval: 1.02-1.07; 8 years in the NPHS, odds ratio = 1.08, 95% confidence interval: 1.03-1.14). We identified a meaningful survival gradient across quartiles of social vulnerability, and although women had better survival than men, survival for women with high social vulnerability was equivalent to that of men with low vulnerability.

Conclusions: Social vulnerability is reproducibly related to individual frailty/fitness, but distinct from it. Greater social vulnerability is associated with mortality in older adults. Further study on the measurement and operationalization of social vulnerability, and of its relationships to other important health outcomes, is warranted.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Composition of the Canadian Study of Health and Aging sample (Panel a) and the National Population Health Survey (Panel b).
Figure 2
Figure 2. Distributions of social vulnerability: A) Canadian Study of Health and Aging (CSHA), B) National Population Health Survey (NPHS) and frailty: C) CSHA, D) NPHS.
While some individuals scored “zero” on the frailty index, no individual was completely free of social vulnerability.
Figure 3
Figure 3. Mean (95% Confidence Interval) social vulnerability in relation to age and sex.
Panel A) In the Canadian Study of Health and Aging, social vulnerability increased with age and women had higher index scores than men at all ages. Panel B) In the National Population Health Survey, women showed a trend towards higher scores at older ages.
Figure 4
Figure 4. Survival by level of social vulnerability.
Panels A (Canadian Study of Health and Aging) and B (National Population Health Survey) show decreasing survival by increasing quartile of social vulnerability. Panels C (CHSA) and D (NPHS) show that although women had better survival than men, survival for women with high social vulnerability was equivalent to that of men with low vulnerability.
Figure 5
Figure 5. ‘Bootstrap by variables’ analyses.
Survival curves show 100 replications of 80% re-sampling within the Canadian Study of Health and Aging social vulnerability index. Panel A – women, Panel B – men.
See this image and copyright information in PMC

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