TLDR
Memory and thinking are shaped by many parts of life, including physical health, daily habits, mood, education, and relationships. Staying active, eating well, and maintaining supportive connections may help, but the evidence about social relationships is still mixed.
Summary
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1 Study Aim
The authors aimed to map factors linked with cognitive health (how well a person thinks and remembers), cognitive decline, and dementia. They especially examined social factors and sought gaps for prevention research. The study also aimed to support an integrated framework combining physical, psychological, and social health. The study examined which parts of life may influence thinking and memory as people age.
2 Study Design
This systematic review of reviews (a structured summary of existing evidence summaries) covered systematic reviews and meta-analyses (studies combining results statistically) published from 2009 to 2021. Two reviewers independently searched Medline, PsycINFO, CINAHL Complete, Cochrane, and Epistemonikos. They screened records, resolved disagreements through discussion, and followed PRISMA 2020 (standard reporting guidance). They included 314 reviews involving adults aged 18 and older. The team grouped reported factors into seven categories and assessed review quality with AMSTAR (a checklist for judging review methods). The researchers combined findings from many earlier studies rather than testing participants directly.
3 Findings
The study identified 624 cognitive-related factors. Risk factors represented 61.2%, while protective factors represented 20%. Somatic comorbidities (coexisting physical illnesses), especially diabetes and cardiovascular disease, and genetic predispositions dominated. Lifestyle protections included the Mediterranean diet, physical activity, and cognitively stimulating activities (mentally challenging activities). Social factors represented 9.6%. Greater support, frequent contact, social participation, and larger networks sometimes related to lower dementia risk, but results were inconsistent. Overall, 81.3% of reports showed significant associations, while 14.3% were unclear. The authors recommend more longitudinal research across the life course, especially on social health, cognitive reserve (the ability to cope with brain changes), lifestyle, and positive psychological factors. Many health habits and relationships may matter, but stronger long-term research is needed before firm advice can be given.