Prevalence of DSM-5 Mild Neurocognitive Disorder in Dementia-Free Older Adults: Results of the Population-Based LIFE-Adult-Study

Objective: The DSM-5 introduces mild neurocognitive disorder (miNCD) as a syndrome that recognizes the potential clinical importance of acquired cognitive deficits being too mild to qualify for diagnosis of dementia. We provide new empirical data on miNCD including total, age-, and sex-specific prevalence rates; number and types of neurocognitive domains being impaired; and diagnostic overlap with the well-established mild cognitive impairment (MCI) concept. Design: Cross-sectional results of an observational cohort study (LIFE-Adult-Study). Setting: General population. Participants: A total of 1,080 dementia-free individuals, aged 60-79 years. Measurements: We calculated weighted point prevalence rates with confidence intervals (95% CI) for miNCD and analyzed diagnostic overlap between miNCD and MCI by calculating overall percentage agreement and Cohen's kappa coefficient. Results: Weighted total prevalence of miNCD was 20.3% (95% CI: 17.8-23.0). Prevalence was similar in both sexes, but significantly higher in older age. Two-thirds (66.2%) of the individuals with miNCD showed impairment restricted to only one out of six possible neurocognitive domains. Learning and memory was the most frequently (38.3%) impaired domain in all miNCD-cases, followed by social cognition (26.1%). Analysis of diagnostic overlap with MCI yielded an overall agreement of 98.6% and a kappa of 0.959. Conclusions: By considering all six predefined neurocognitive domains, our study observed a substantial proportion of dementia-free older adults having miNCD. Provision of information on the underlying etiology/ies may be of prime importance in future studies aiming at evaluating the clinical relevance of the miNCD syndrome.