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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.
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Showing 6 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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| Exposure | Question | Direction | Outcome measured | Design | People | Effect size, as the source reported it | Source |
|---|---|---|---|---|---|---|---|
| Sex differences (biological sex as exposure) All modifiable factors together | Prevention |
Harm
whyDirection is for female sex: women had higher odds of a high neuritic plaque burden than men after adjustment, and were more likely to reach Braak stage V-VI. Black non-carriers and non-carriers of African ancestry were least likely to have high plaque burden, a protection weakened in ε4 carriers. |
Neuritic plaque burden (CERAD score) at autopsy by sex, and its interaction with APOE ε4, race and African ancestry | cross-sectional study | 2,268 | Female individuals had higher plaque burden than male individuals (unadjusted odds ratio [OR], 1.97; 95% CI, 1.67-2.29; P < .001), and this association remained significant in adjusted models for sociodemographic and vascular factors and APOEε4 status (adjusted OR, 1.65; 95% CI, 1.33-2.20; P < .001). APOEε4 carriers of both sexes had an approximately 4-fold greater odds of plaques |
JAMA neurology
2026 ✓ Peer-reviewed PMID 41729539 |
| Blood biomarker test (p-tau217 / amyloid ratio) Care, carers and services | Treatment |
Harm
whyDirection is for chronic kidney disease as a source of false signal: at eGFR 45 versus 60, p-tau217 was 31-55% higher in amyloid-negative people on two immunoassays, a rise largely removed by using the %p-tau217 ratio. A test-validity result, not a health outcome. |
Plasma p-tau217 concentration by kidney function (eGFR) in amyloid-negative and amyloid-positive people | cross-sectional study | 202 | For an eGFR of 45 vs 60 in the A- cohort, the calculated percentage changes were +31%, +55%, and +19%, for ALZpath p-tau217, C2N p-tau217, and C2N %p-tau217, respectively. For the A+ cohort, the corresponding calculated percentage changes were +17%, +15%, and -5%, respectively |
Neurology
2025 ✓ Peer-reviewed PMID 39823562 |
| Blood biomarkers (GFAP, NfL, p-tau217) for staging and prognosis Care, carers and services | Treatment |
Harm
whyDirection is for microglial activation: amyloid was associated with astrocyte reactivity across cortical regions only when microglia were activated, and that microglia-dependent reactivity related to cognitive impairment through tau phosphorylation and aggregation. |
Astrocyte reactivity (plasma GFAP) in relation to amyloid PET and microglial activation PET, and downstream tau and cognitive impairment | cross-sectional study | 352 | not established — pubmed abstract reports no numeric effect size. |
Nature Neuroscience
2026 ✓ Peer-reviewed PMID 41198899 |
| Cost of dementia care Care, carers and services | Treatment |
Harm
whyDirection is for being on the Alzheimer's continuum: societal costs were 52% higher in subjective cognitive decline, 170% in MCI and 307% in AD dementia than in controls, and payer costs 26%, 85% and 36% higher. A cost result, not a health outcome. |
Excess annual costs from payer and societal perspectives in subjective cognitive decline, MCI and AD dementia versus controls | cross-sectional study | not stated | From a payer perspective, costs were elevated by 26% for SCD (adjusted mean 5,976€ [95%CI 4,598-7,355€]), 85% for MCI (8,795€ [6,200-11,391€]) and 36% for AD (6,454€ [2,796-10,111€]) compared to controls (4,754€ [3,586-5,922€]). Societal costs were elevated by 52% for SCD (adjusted mean 8,377€ [95%CI 6,009-10,746€]), 170% for MCI (14,886€ [9,524-20,248€]) and 307% for AD (22,481€ [9,994-34,969€]) compared to controls (5,522€ [3,814-7,230€]) |
Alzheimer's research & therapy
2025 ✓ Peer-reviewed PMID 40571933 |
| Cost of dementia care Care, carers and services | Treatment |
Harm
whyDirection is for living in the community rather than a nursing home: unadjusted costs were lower in the community, but after adjusting for functional impairment and comorbidity community care cost €11,344 more per year, mainly through informal care. A cost result, not a health outcome. |
Annual societal cost of care, community-dwelling versus nursing home residents | cross-sectional study | 176 | Unadjusted mean annual total costs including informal care were €29,930 ($43,997) for community-dwelling patients and €33,482 ($49,218) for patients living in nursing homes. However, multiple regression analysis controlling for age, sex, deficits in basic and instrumental activities of daily living and comorbidity showed that living in the community significantly increased total costs by €11,344 ($16,676; P < .01) compared with living in a nursing home, mainly due to higher costs of informal care (+€20,585; +$30,260; P < .001) |
Journal of the American Medical Directors Association
2014 ✓ Peer-reviewed PMID 24321877 |
| Tau PET imaging (natural history of tau) Care, carers and services | Treatment |
Harm
whyDirection is for regional tau burden: more tau went with less glucose metabolism (r = -0.49) and with worse domain-specific cognition, while amyloid was diffuse and only weakly related. An imaging association, not an exposure effect. |
Regional glucose hypometabolism and domain-specific cognitive deficits | cross-sectional study | 35 | there was a strong negative association between (18)F-AV1451 and (18)F-FDG uptake (Pearson's r = -0.49 ± 0.07, P < 0.001) and less pronounced positive associations between (11)C-PiB and (18)F-FDG (Pearson's r = 0.16 ± 0.09, P < 0.001) and (18)F-AV1451 and (11)C-PiB (Pearson's r = 0.18 ± 0.09, P < 0.001) |
Brain
2016 ✓ Peer-reviewed PMID 26962052 |