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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
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

Eight kinds of sleep disturbance were analysed; both short and long sleep carried higher risk, as did excessive daytime sleepiness and insomnia.

 Cognitive decline or dementia meta-analysis not stated Excessive daytime sleepiness RR 1.41 for all-cause dementia; long sleep RR 1.66 for Alzheimer's disease Journal of Neurology 2025
✓ Peer-reviewed PMID 41081870
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

No significant association with vascular dementia, and none of the 11 studies used biomarkers to confirm the diagnoses.

 Any neurocognitive disorder; Alzheimer's disease meta-analysis 1,333,424 HR 1.43 (95% CI 1.26-1.62) for any neurocognitive disorder; Alzheimer's HR 1.28 (1.16-1.41) Journal of Sleep Research 2022
✓ Peer-reviewed PMID 35366021
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

Persisted after controlling for depression and social isolation.

 Incident all-cause dementia meta-analysis 608,561 All-cause dementia HR 1.306 (95% CI 1.197-1.426); Alzheimer's disease HR 1.393 (95% CI 1.290-1.504, 5 samples); vascular dementia HR 1.735 (95% CI 1.483-2.029, 3 samples); cognitive impairment HR 1.150 (95% CI 1.113-1.189, 16 samples) Nature Mental Health 2024
✓ Peer-reviewed PMID 39802418
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

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