Predictors of frailty in old age–results of a longitudinal study (original) (raw)

2015, The journal of nutrition, health & aging

Since 1991 the term "frail elderly" has been a Medline Medical Subject Heading and is defined as "older adults or aged individuals who are lacking in general strength and are unusually susceptible to disease or to other infirmity". Thus, frailty can be characterized by increased vulnerability to stressors and a lack of physiological reserve (1, 2). Due to demographic ageing, the prevalence of frailty is expected to increase considerably (3). It is well-known that frailty is a major predictor of mortality (4, 5) and institutionalization [6] as well as other adverse health outcomes (5, 7-16), underlining the need for interventional strategies. Numerous cross-sectional studies have examined factors associated with frailty (17-23). However, these studies fail to identify causal mechanisms. Longitudinal studies are needed in order to get insights into the causality. Yet, only a few studies (24-29) have investigated the predictors of frailty in old age longitudinally. Most of these studies used a static set of baseline characteristics as predictors. Thus, they could not account for changes in these characteristics. So far, only very few longitudinal (30-32) studies have investigated how changes in predictors affect frailty. Yet, in order to identify causal effects it is crucial to examine changes in predictors. The aim of our study was to identify time-dependent factors affecting frailty in old age. Therefore, we investigated time-dependent variables which may be relevant for frailty, including sociodemographic (26, 33), psychological (25-27, 34) and cognitive factors (26, 35) as well as comorbidity (26) in a longitudinal approach. Knowledge of the factors leading to frailty in a longitudinal setting is important in order to develop strategies for prevention or delay of frailty. Methods Sample Data were used from the German Study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe) which is a population based prospective cohort study. At six study centers in Germany (Leipzig, Hamburg, Dusseldorf, Mannheim, Bonn and Munich) individuals were recruited by general practitioners' (GP) offices, beginning in 2003/2004. From this time onwards, trained staff interviewed individuals as well as their proxies every 18 months. Thus, follow-up (FU) wave 5 took place in 2011/2012. Individuals were only included in the sample, if they met three conditions at baseline (n=3,217): 75 years and older, absence of dementia and at least one contact with the GP during the last 12 months. If they met at least one of the following conditions at baseline, individuals were excluded: insufficient knowledge of the German language, consultations only via