The Ubiquity of Cognitive Impairment in Human Illness: a Systematic Review of Meta-Analyses

Objective: Cognitive dysfunction occurs in many neurological, psychiatric, and other health conditions. This review aimed to characterize the breadth and degree of cognitive morbidity associated with varied health conditions. Method: We systematically reviewed Medline, EMBASE, and Cochrane databases for meta-analyses of cognitive dysfunction associated with any health condition. Meta-analyses were eligible if they reviewed studies that compared patients with health conditions to healthy controls on cognitive testing and provided effect sizes. Results: We found 91 meta-analyses for 94 health conditions. Among >800,297 participants, healthy controls out-performed clinical participants in every condition on cognitive testing. Mean effect sizes ranged from -2.02 to -0.00 across conditions and were <= -0.5 on average, denoting moderate to very severe dysfunction for 41% of them. Conclusions: Cognitive dysfunction is ubiquitous in medicine. Both primary care and specialist physicians likely treat patients with cognitive dysfunction. Depending on its severity, cognitive dysfunction can affect treatment adherence, everyday functioning, quality of life, and the capacity to provide informed consent for treatment. These findings highlight the transdiagnostic nature of cognitive symptoms and the potential value of establishing collaborations between physicians and clinical neuropsychologists to integrate cognitive assessment into patient care. Even brief assessments can identify cognitive deficits that likely affect treatment adherence and functional outcomes.