OBJECTIVES: Persons with mild cognitive impairment (MCI) have a substantial likelihood of progressing to Alzheimer’s disease dementia or another dementia. MCI prevalence estimates can help inform public health agencies and clinical decision-makers. Published reviews detailing MCI prevalence in the general population include a broad range of estimates. We provide age-specific MCI prevalence proportions in the Americas, Europe and Australia and examine potential sources of heterogeneity.

METHODS: We conducted a systematic literature review of population-based studies that estimated prevalence proportions in 5-year age categories using standard definitions of MCI, which include the requirement for subjective cognitive complaints. Stringent eligibility criteria were applied in an attempt to limit study heterogeneity. Using a multi-pronged approach, data were synthesized by quantitative and qualitative descriptive analyses and quantitative meta-analyses.

RESULTS: We identified 900 articles, of which 9 studies were retained for analysis. Meta-analysis estimates and 95% CIs of MCI prevalence were: 10.7 (6.6-15.7) for 65-69 y, 11.9 (6.2-19.2) for 70-74 y, 12.4 (7.0-19.0) for 75-79 y, 11.9 (6.1-19.2) for 80-84 y, and 14.5 (7.1-23.9) for 85+ y. Heterogeneity in prevalence estimates (as measured by I) remained despite rigorous inclusion criteria. The qualitative assessment indicated that the included studies are real-world relevant and use high-quality methods, with no single apparent explanation for heterogeneity, thus supporting the relevance of the meta-analysis summary ranges. Prevalence estimate ranges identified in this study were largely consistent with those published in as part of the American Academy of Neurology’s 2018 MCI guidelines.

CONCLUSIONS: This systematic literature review provides estimates of the prevalence of MCI in the Americas, Europe and Australia and highlights real-world challenges in providing a consistent estimate for this population. Challenges include: difficulties in achieving reliable diagnosis, operationalization of diagnostic criteria, study methodological differences, multiple etiologies of MCI. Due to the remaining heterogeneity, quantitative ranges are important to consider with summary point estimates.