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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 4 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, 4 rows. Every row links to its source.
Exposure Question Direction Outcome measured Design People Effect size, as the source reported it Source
Hearing loss / hearing aids Hearing and vision Prevention Harm
why

Direction is for having the impairment. Dual sensory impairment carried the highest risk (HR 1.63 for all-cause dementia, 2.55 for Alzheimer's).

 All-cause and cause-specific dementia meta-analysis 937,908 Hearing impairment: pooled HR 1.30 (95% CI 1.21-1.40); dual sensory impairment HR 1.63 (1.14-2.12) for all-cause dementia BMC Medicine 2024
✓ Peer-reviewed PMID 39506811
Hearing loss / hearing aids Hearing and vision Prevention Benefit
why

Mostly observational (25 of 31 studies), so people who take up hearing aids may differ from those who do not. The authors call for randomised trials — and ACHIEVE, the trial that followed, was null overall.

 Long-term cognitive decline meta-analysis 137,484 HR 0.81 (95% CI 0.76-0.87) for cognitive decline with hearing aid use JAMA Neurology 2023
✓ Peer-reviewed PMID 36469314
Vision impairment / cataract surgery Hearing and vision Prevention Benefit
why

Against untreated cataract. People who had surgery ended up at about the same risk as controls who never had cataracts (HR 0.84, 95% CI 0.66-1.06), and there was no short-term gain in those already cognitively impaired.

 Long-term cognitive decline / dementia meta-analysis 558,276 HR 0.75 (95% CI 0.72-0.78) for cognitive decline with surgery Ophthalmology 2024
✓ Peer-reviewed PMID 38336283
Vision impairment / cataract surgery Hearing and vision Prevention Harm
why

Direction is for having a vision impairment. Single vision impairment raised all-cause dementia risk but not Alzheimer's specifically; having both hearing and vision impairment carried the highest risk.

 All-cause and cause-specific dementia meta-analysis 937,908 UK Biobank cohort: vision impairment and all-cause dementia HR 1.55 (95% CI 1.18-2.04) and non-Alzheimer non-vascular dementia HR 1.51 (1.07-2.13). Meta-analysis of 31 cohorts: single vision impairment and all-cause dementia HR 1.43 (95% CI 1.16-1.71), not significant for Alzheimer's. Mendelian randomisation: vision impairment and non-AD non-VD OR 1.62 (95% CI 1.13-2.33). Dual sensory impairment: all-cause dementia HR 1.63 (1.14-2.12) BMC Medicine 2024
✓ Peer-reviewed PMID 39506811

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