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Home › Research › What the research found › Every row

Every row of the evidence table

One row per finding: what was tested, which way the result went, and how the study was built. The answer by area, and where the studies disagree, are on the main page.

Every row

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Area All 382 Care, carers and services 140 Medicines 85 Genes (not modifiable) 35 All modifiable factors together 27 Diet and supplements 23 Exercise and activity 21 Sleep, mood and social life 19 Hearing and vision 8 Alcohol, tobacco and cannabis 6 Infection and vaccination 5 Heart and metabolic health 4 Injury, delirium and falls 4 Environment 3 Cognitive activity 2
Question Both Prevention 190 Treatment 192
Direction Any Benefit 144 Harm 105 No effect 38 Mixed 37 No direction reported 58
Design Any meta-analysis 57 randomised trial 44 phase 3 trial 15 systematic review 9 phase 2 trial 10 cohort study 136 phase 1 trial 2 cross-sectional study 31 case-control study 14 modelling study 20 regulatory decision 7 company announcement 1 coverage determination 1 None 35
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Showing 9 of 382 rows. One row per study per exposure: a study that tested two different things appears twice, once for each.

Scroll the table sideways to see every column.

Research and outcomes, 9 rows. Every row links to its source.
Exposure Question Direction Outcome measured Design People Effect size, as the source reported it Source
Depression Sleep, mood and social life Prevention Harm
why

The authors read these symptoms as early markers of neurodegeneration rather than causes — which is also how an earlier analysis of this same cohort read its own null result for midlife depression.

 Incident dementia over a mean 22.6 years cohort study 5,811 HR 1.29-1.51 for six specific midlife depressive symptoms Lancet Psychiatry 2026
✓ Peer-reviewed PMID 41412145
Depression Sleep, mood and social life Prevention Harm
why

Direction is for having depression (51% higher risk). Treated depression carried lower risk than untreated (HR 0.7), which is the more interesting half but is an observational comparison of people who did and did not get treatment.

 Incident dementia cohort study 354,313 Depression treatment HR 0.7 (95% CI 0.62-0.77) for incident dementia vs untreated depression Biological Psychiatry 2023
✓ Peer-reviewed PMID 36526487
Depression Sleep, mood and social life Prevention No effect
why

Midlife depressive symptoms did not raise dementia risk (HR 1.21, 95% CI 0.95-1.54), even when chronic. The association closer to diagnosis is read by the authors as depression being a prodromal feature, not a cause.

 Incident dementia over 28 years cohort study 10,189 Depressive symptoms at the 2003 ("late-life") assessment: HR 1.72 (95% CI 1.21-2.44) for dementia; chronic/recurring symptoms in the late phase: HR 1.67 (95% CI 1.11-2.49); early-life (1985) depressive symptoms not significant: HR 1.21 (95% CI 0.95-1.54) JAMA Psychiatry 2017
✓ Peer-reviewed PMID 28514478
Education / cognitive reserve Sleep, mood and social life Prevention Benefit
why

Direction is for MORE education. Up to a quarter of the effect ran through midlife vascular risk factors, and the authors say treating those factors would not close the educational gap.

 Incident dementia cohort study 13,368 8-44% lower dementia risk with higher education vs grade school; up to 25% mediated by midlife vascular risk factors Annals of Neurology 2023
✓ Peer-reviewed PMID 36966451
Genetic risk disclosure Sleep, mood and social life Prevention Harm
why

Distress rose, and rose most in APOE4 homozygotes. The authors nonetheless conclude disclosure by a trained provider was generally safe and well tolerated in this psychologically pre-screened group.

 Disease-specific distress 2-7 days after disclosure cohort study 9,496 Disease-specific distress change at 2-7 days: +2.25 (homozygotes) vs +0.53 (heterozygotes) vs +0.79 (non-carriers) The Lancet Healthy Longevity 2025
✓ Peer-reviewed PMID 41319675
Sleep Sleep, mood and social life Prevention Harm
why

Direction is for LOSING slow-wave sleep. 52 cases in 346 people, so the estimate is imprecise, and slow-wave sleep also falls with Alzheimer's genetic risk, which muddies cause and effect.

 Incident dementia over 17 years cohort study 346 HR 1.27 (95% CI 1.06-1.54) per 1%/year loss of slow-wave sleep JAMA Neurology 2023
✓ Peer-reviewed PMID 37902739
Sleep Sleep, mood and social life Prevention Harm
why

Direction is for SHORT sleep (6 hours or less): higher dementia risk than a 7-hour sleep duration.

 Incident dementia over 25 years cohort study 7,959 HR ~1.22 (age 50) and ~1.37 (age 60) for short vs. 7-hour sleep; persistent short sleep across ages 50/60/70 ~30% higher risk Nature Communications 2021
✓ Peer-reviewed PMID 33879784
Social isolation / loneliness Sleep, mood and social life Prevention Harm
why

Isolation (being alone) carried the risk (HR 1.26); loneliness (feeling alone) did not once depressive symptoms were accounted for (HR 1.04, 95% CI 0.94-1.16). That split matters, and the loneliness meta-analysis here reaches the opposite conclusion about loneliness.

 Incident dementia over a mean 11.7 years cohort study 462,619 Social isolation HR 1.26 (95% CI 1.15-1.37) for incident dementia Neurology 2022
✓ Peer-reviewed PMID 35676089
Social isolation / loneliness Sleep, mood and social life Prevention Benefit
why

Significant only for contact measured at age 60, not at 50 or 70. The authors note that keeping up contact may itself be a marker of cognitive reserve rather than a cause of it.

 Incident dementia over 28 years cohort study 10,228 HR 0.88 per SD higher social contact frequency at age 60 (95% CI 0.79-0.98) PLoS Medicine 2019
✓ Peer-reviewed PMID 31374073

How this table was built, and where it is weak →