Every finding in the evidence table: 382 rows, filterable

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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

Showing 8 of 382 rows. One row per study per exposure: a study that tested two different things appears twice, once for each.

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Research and outcomes, 8 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	Benefit why Confined to people who said the aid actually improved their hearing (HR 0.86); those reporting poor improvement showed nothing (HR 0.98).	Probable dementia over a mean 6.5 years	cohort study	61,089	HR 0.91 (95% CI 0.88-0.94) for hearing aid use; HR 0.86 (0.80-0.93) with effective use	Cell Reports Medicine 2026 ✓ Peer-reviewed PMID 42127901
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	Harm why Direction is for hearing loss. Risk was lower among those using hearing aids (aHR 1.06) than those not (aHR 1.20). The authors note their estimates are smaller than earlier studies'.	Incident dementia over a mean 8.6 years	cohort study	573,088	Hearing loss without hearing aids aHR 1.20 (95% CI 1.13-1.27); with hearing aids aHR 1.06 (1.01-1.10)	JAMA Otolaryngology-Head & Neck Surgery 2024 ✓ Peer-reviewed PMID 38175662
Hearing loss / hearing aids Hearing and vision	Prevention	No effect why Null in the primary analysis of the whole cohort. The prespecified analysis of the higher-risk ARIC subgroup found less decline, which the authors present as hypothesis-generating rather than as a result.	3-year global cognition (primary analysis)	randomised trial	977	Primary analysis: "3-year cognitive change (in SD units) was not significantly different between HI and SA control (HI: -0.200 [95% CI: -0.256, 0.144]; SA: -0.202 [95% CI: -0.258, -0.145]; Difference 0.002 [95% CI: -0.077, 0.081], p=0.96)." ARIC subgroup: "HI was associated with a 48% reduction in 3-year cognitive change compared to SA control (Difference 0.191 [95% CI: 0.022, 0.360], p=0.027)."	The Lancet 2023 ✓ Peer-reviewed PMID 37478886
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
Vision impairment / cataract surgery Hearing and vision	Prevention	Harm why Direction is for having cataracts or myopia. A Mendelian randomisation analysis supported the cataract-vascular dementia link.	Incident dementia and brain volume	cohort study	304,953	Cataracts HR 1.18 (95% CI 1.07-1.29) for dementia; MR OR 1.92 (1.26-2.92) for vascular dementia	JAMA Network Open 2024 ✓ Peer-reviewed PMID 39078629

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