Cognitive function and all-cause mortality in a population-based nationwide sample of older adults

Background

Germany’s declining life expectancy relative to Western Europe necessitates identifying key mortality risk factors. This study estimates the causal effect of cognition on all-cause mortality among older adults in a population-based nationwide survey in Germany.

Methods

Mortality status of 1,794 participants aged 65 to 79 years from the German Health Interview and Examination Survey for Adults (DEGS1, 2008-2011) was ascertained in 2024-2025. Baseline cognitive function assessed by the Digit Symbol Substitution Test was z-standardized using age-, sex-, and education-specific normative data. A z-score < -1 was defined as cognitive impairment. Weighted Cox regression estimated the effect of continuous cognitive function on all-cause mortality adjusted for confounders based on a directed acyclic graph. Multiple imputations were used to handle missing data.

Results

The mean observation time was 12.2 years. A total of 146 individuals with cognitive impairment (48%) and 515 individuals without cognitive impairment (35%) died. For every one-unit increase in the standard deviation towards better cognitive function, the hazard for all-cause mortality decreased by 23% (Hazard ratio: 0.77, 95%-confidence interval: 0.71-0.85), adjusted for sociodemographics, health risk behaviors, certain chronic diseases and sensory limitations. Sensitivity analyses using complete cases yielded robust findings.

Conclusions

Higher cognitive function protects against all-cause mortality, highlighting the crucial role of brain health in healthy ageing. Germany needs a comprehensive and coherent brain health initiative through individual and population-based measures. The continuation of Germany’s national dementia strategy beyond 2026 and participation in the EU joint action “JADE Health” offer key opportunities for this goal. Moreover, since many NCDs share similar risk factors, a comprehensive prevention and Public Health strategy is needed to improve Germany’s life expectancy.

Key messages

• Cognitive function is an important factor of longevity in older adults.

• Brain health initiatives could strengthen an overall prevention strategy for improving life expectancy and healthy aging.