Frailty among older adults in Germany: regional variation across NAKO study centers

Frailty is a geriatric syndrome associated with increased morbidity, disability, and mortality. While its prevalence has been studied extensively in individual cohorts and patient populations, national prevalence data are scarce and regional variations within Germany remain largely unexplored. This study examined the frequency of frailty and its regional variation across the 18 NAKO (German National Cohort) study centers using a uniform frailty index.

We analysed baseline data collected between 2014 and 2019 from 39,248 participants aged 61-75 years enrolled in the NAKO study, a large population-based cohort recruited across 18 study centers in Germany. Frailty was measured using a 40-item Frailty Index (FI), with FI ≥ 0.25 indicating frailty. Regional variations in frailty were first examined using crude frequencies and subsequently analysed with logistic regression, adjusting for key confounders, including age, sex, and sociodemographic and socioeconomic factors, to account for compositional differences across centers.

The crude frequency of frailty in the total sample was 7.7% (95% CI: 7.5-8.0), while 34.1% were prefrail. Frailty frequencies showed a nearly twofold spread (5.4%-10.2%) across study sites, being highest in Essen, Düsseldorf, Regensburg, Saarbrücken, and Berlin, and lowest in Freiburg, Münster, and northern German centers. Higher age, lower socioeconomic status and weaker social networks were all independently associated with frailty status. However, while these compositional factors contributed to the variability observed across centers, they did not fully account for it.

Notable regional differences in frailty are evident across NAKO study centers in Germany, even after accounting for population composition (age, sex, and socioeconomic factors). This residual heterogeneity suggests that contextual factors - such as regional healthcare access, environmental exposures, or structural policies - contribute to frailty development beyond individual risk factors.