Predictability of frailty index and its components on mortality in older adults in China
Yang and Gu BMC Geriatrics
Predictability of frailty index and its components on mortality in older adults in China
Fang Yang 1
Danan Gu 0
0 United Nations Population Division , Two UN Plaza, DC2-1910, New York, NY 10017 , USA
1 Department of Social Work, School of Sociology and Political Science, Shanghai University , Shanghai , China
Background: Frailty represents an increased vulnerability to external stressors due to decreased physiological reserve and dysfunction in multiple bodily systems. The relationship between frailty and mortality has been well-documented in the literature. However, less is known about the predictive powers of frailty index and its components on mortality when they are simultaneously present. This study aimed to examine the predictive powers of frailty index and its multiple components on mortality in a nationally representative sample of older adults in China. Methods: We used a sample of 13,731 older adults from the 2008/2009 and 2011/2012 waves of the Chinese Longitudinal Healthy Longevity Survey (CLHLS). Frailty was measured using the cumulative deficit approach, and was constructed from 38 health variables (39 deficits). We selected 8 major sets of components: activities of daily living (ADL) (6 deficits), instrumental ADL (IADL) (8 deficits), functional limitations (5 deficits), overall cognitive functioning (1 deficit), chronic disease conditions (11 deficits), self-reported health (2 deficits), hearing and vision impairment (2 deficits), and psychological distress (1 deficit). Survival analysis was used to examine the roles of the frailty and its components in mortality. Results: Results showed that almost all the components of the frailty index (except chronic diseases) were significant predictors of mortality when examined individually. Among the components, ADL and IADL disabilities remained significant when considering all the components simultaneously. When the frailty and its components were simultaneously analyzed, the frailty remained a robust predictor of mortality across the age and sex groups, while most components lost their significance except ADL, IADL, and cognitive function components in some cases. Conclusions: Frailty measured by cumulative deficits has a stronger predictive power on mortality than its all individual components. ADL and IADL disability play a greater role in mortality than other components when considering all the components of frailty.
Frailty index; Frailty components; Mortality; Older adults; CLHLS; China
Background
Frailty has received increasing academic attention in the
field of gerontology and geriatrics in the past 30 years
[
1–4
]. Frailty represents multifactorial vulnerability to
external stressors due to decreased physiological reserve
and dysregulation in multiple bodily systems [
1, 3, 5–8
].
Despite the heated discussion on this topic, there is no
consensus regarding the measures of frailty [
1, 3, 9
].
However, there are two widely used models to measure
frailty: one is the phenotype model and the other is the
health deficit accumulation model. The former assesses
frailty using five specific manifest indicators, including
unintentional weight loss, exhaustion, low physical
activity, slowness, and weakness [
1
]. The latter measures
frailty using the proportion of present deficits to all
the possible health deficits in physical, functional, and
psychosocial domains for a given person, or frailty
index [
3, 7, 10
]. Different from the phenotype model,
frailty index focuses more on the aggregate decline in
psychosocial and physical functioning, and it is a
promising proxy measure for biological aging [
5, 6, 9, 11
].
Research has demonstrated that frailty is a significant
predictor of a variety of outcomes, such as falls,
hospitalization, health change, and mortality, and the
relationships between frailty and the outcomes are
independent of various confounders and chronological age [
5–7,
10, 12–14
]. Taking mortality for example, the
frailtymortality association has been well-established in the
literature. For instance, empirical research has shown that
frailty index predicts mortality in general older populations
and even in centenarians, for both women and men [
2, 6,
10, 12
], and in older adults from different cultural
backgrounds [
6, 9, 12, 15
].
Regarding the variables used to construct frailty index,
several criteria have to be met. The variables should cover
a range of health deficits, the prevalence of the overall
deficits should generally increase with age, and they should
not saturate too early [
16
]. So far, the following
components have been commonly used to construct frailty index:
cognitive impairment, chronic illness, disability in
activities of daily living (ADL), disability in instrumental
activities of daily living (IADL), functional limitation, self-rated
health, chronic disease conditions, hearing and vision
losses, and psychological distress [
2, 3, 5–7, 12, 13, 16
].
So (...truncated)