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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 3 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, 3 rows. Every row links to its source.
Exposure Question Direction Outcome measured Design People Effect size, as the source reported it Source
Air pollution Environment Prevention Harm
why

Heterogeneity was high (I-squared 95%). Reaches a firmer conclusion than the earlier BMJ meta-analysis of largely the same literature.

 Incident dementia meta-analysis 24,030,527 PM2.5 HR 1.08 per 5 ug/m3 (95% CI 1.02-1.14); NO2 HR 1.03 per 10 ug/m3 (1.01-1.05) Lancet Planetary Health 2025
✓ Peer-reviewed PMID 40716448
Air pollution Environment Prevention Mixed
why

The overall PM2.5 estimate includes no effect (HR 1.04, 95% CI 0.99-1.09). Only the studies that actively assessed everyone for dementia showed a clear effect (HR 1.42, 95% CI 1.00-2.02). Most studies were at high risk of bias.

 Clinically diagnosed dementia meta-analysis not stated PM2.5 HR 1.04 per 2 ug/m3 (95% CI 0.99-1.09) overall; 1.42 (1.00-2.02) with active case ascertainment BMJ 2023
✓ Peer-reviewed PMID 37019461
Traffic / road proximity Environment Prevention Harm
why

Dose-response by distance for dementia; no association with Parkinson's disease or multiple sclerosis.

 Incident dementia cohort study 2,200,000 Adjusted HR 1.07 (95% CI 1.06-1.08) for dementia among people living <50m from a major road vs >300m; HR 1.04 (95% CI 1.02-1.05) for 50-100m The Lancet 2017
✓ Peer-reviewed PMID 28063597

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