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
Filter
Showing 18 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.
| Exposure | Question | Direction | Outcome measured | Design | People | Effect size, as the source reported it | Source |
|---|---|---|---|---|---|---|---|
| APOE and TREM2 risk variants (post-mortem brain) Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying APOE and TREM2 risk variants, which were associated with a significant reduction in amyloid-responsive microglia, read by the authors as a diminished cellular response to amyloid. A tissue result, not a clinical outcome. |
CD163-positive amyloid-responsive microglia in post-mortem Alzheimer brain | None | 48 | not established — pubmed abstract states a "significant reduction" without a figure. |
Acta Neuropathologica
2020 ✓ Peer-reviewed PMID 32840654 |
| APOE genotype Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying APOE ε4: 10-year dementia risk ratios of 1.59 (Filipino, confidence interval crossing 1) to 1.96 (Japanese), similar across the four groups despite carrier prevalence ranging from 14% to 25%. Not modifiable. |
10-year dementia risk by APOE ε4 carriership in Chinese, Japanese, Filipino and non-Latino White adults | cohort study | 46,325 | 10-year risk ratios (95% confidence interval [CI]) ranged from 1.59 (0.66-3.10) among Filipino to 1.96 (1.36-2.78) among Japanese participants |
Alzheimer's & Dementia
2026 ✓ Peer-reviewed PMID 42427166 |
| APOE genotype Genes (not modifiable) | Prevention |
Harm
whyDirection is for each additional ε4 allele: it did not change amyloid-related p-tau217 secretion, but for any given p-tau217 level tau spread faster across connected regions, and the p-tau217 threshold marking early tau-PET increases was 26-76% lower than in non-carriers. |
Amyloid-associated plasma p-tau217 increase, and p-tau217-associated tau-PET spread, by APOE ε4 allele count | cohort study | 401 | plasma ptau217 elevations were linked to faster tau-PET spread from local epicentres across connected brain regions in an ApoE4 allele dose-dependent manner, independent of amyloid [ADNI/A4-LEARN: mean standardized beta (β) = 0.44/0.56, P < 0.001/P < 0.001] ... (ADNI: 0/1/2 ApoE4 alleles = 0.62/0.34/0.15 pg/ml, representing ∼45% and ∼76% reductions from non-carriers; Fujirebio ptau217 assay; A4-LEARN: 0/1/2 ApoE4 alleles = 0.31/0.23/0.18 pg/ml, representing ∼26% and ∼42% reductions; Eli Lilly ptau217 assay) |
Brain
2026 ✓ Peer-reviewed PMID 41410687 |
| APOE genotype Genes (not modifiable) | Prevention |
Harm
whyDirection is for the APOE4 allele, whose effect ranged from OR 2.22 in Caribbean-Hispanic to 6.13 in Peruvian/Bolivian participants. The APOE2 allele went the other way (OR 0.81). Not modifiable. |
Alzheimer's disease and related dementias (odds ratio) | case-control study | 12,221 | APOE ε4 meta-analytic OR 2.32 (95% CI 2.09-2.57); range 2.22 (Caribbean-Hispanics) to 6.13 (Peruvians/Bolivians) |
Alzheimer's & Dementia
2025 ✓ Peer-reviewed PMID 40219824 |
| APOE genotype Genes (not modifiable) | Prevention |
Harm
whyDirection is for APOE ε4 carriage, which strengthened the association between amyloid and plasma p-tau; plasma GFAP strengthened the p-tau-tau PET link mainly in non-carriers, and high GFAP went with faster longitudinal tau accumulation. |
Strength of the amyloid-p-tau and p-tau-tau PET associations by APOE ε4 status and plasma GFAP, and longitudinal tau accumulation | cohort study | 806 | stronger Aβ–pTau associations observed in APOE ε4 carriers (CPAS: β = 0.26, p = 0.003 for pTau231; ADNI: β = 0.45, p < 0.001 for pTau181) |
Molecular Neurodegeneration
2025 ✓ Peer-reviewed PMID 41163175 |
| APOE genotype Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying two APOE4 copies: near-complete penetrance of Alzheimer's biology and earlier symptom onset. |
Alzheimer's biomarkers and age at symptom onset | cohort study | 10,039 | Nearly all APOE4 homozygotes showed Alzheimer's pathology by age 55 vs. about half of non-carriers |
Nature Medicine
2024 ✓ Peer-reviewed PMID 38710950 |
| APOE genotype Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying APOE*4: the ε3/ε4 odds ratio fell stepwise from 4.54 in East Asian to 3.46 in White, 2.18 in Black and 1.90 in Hispanic individuals; ε2 was protective in White and Black but not Hispanic or East Asian individuals. Not modifiable. |
Odds of Alzheimer's disease by APOE genotype, across ancestry, sex and age | case-control study | 68,756 | Odds ratios for APOE*34 and AD risk attenuated following East Asian (OR, 4.54; 95% CI, 3.99-5.17),White (OR, 3.46; 95% CI, 3.27-3.65), Black (OR, 2.18; 95% CI, 1.90-2.49) and Hispanic (OR, 1.90; 95% CI, 1.65-2.18) individuals. Similarly, ORs for APOE*22+23 and AD risk attenuated following White (OR, 0.53, 95% CI, 0.48-0.58), Black (OR, 0.69, 95% CI, 0.57-0.84), and Hispanic (OR, 0.89; 95% CI, 0.72-1.10) individuals |
JAMA Neurology
2023 ✓ Peer-reviewed PMID 37930705 |
| Polygenic risk / GWAS loci Genes (not modifiable) | Prevention |
Harm
whyDirection is for midlife hypertension. Genetic risk for Alzheimer's did not modify it, which the authors read as everyone with hypertension standing to gain from treatment. |
Incident dementia over 23-27 years | cohort study | 11,597 | Midlife hypertension HR for dementia 1.19-1.34 across genetic risk tertiles (white participants); 1.31 (95% CI 1.04-1.66) in high-risk Black participants |
Neurology
2026 ✓ Peer-reviewed PMID 42385118 |
| Polygenic risk / GWAS loci Genes (not modifiable) | Prevention |
Harm
whyDirection is for a high polygenic score (excluding APOE): people in the top decile had a twofold risk of Braak stage >4 tangles and of moderate-to-severe amyloid plaque pathology at death. 91 loci identified, 16 new; 18 further loci await validation. |
Genome-wide risk loci and a polygenic score's association with tau and amyloid pathology at death | meta-analysis | 978,514 | We identified 91 genetic loci associated with ADRD risk, of which 16 are new and 56 are specifically detected in clinically diagnosed AD cases ... Individuals in the tenth decile of the score exhibited a twofold increased risk of presenting with Braak neurofibrillary tangles stage of >4 and moderate-to-severe neuritic amyloid plaque pathology at death compared to individuals in the median score group |
Nature Genetics
2026 ✓ Peer-reviewed PMID 42237039 |
| Polygenic risk / GWAS loci Genes (not modifiable) | Prevention |
Harm
whyDirection is for a higher polygenic score: each standard deviation raised AD odds 1.14-1.52-fold across European, African American, Caribbean Hispanic and Native American Hispanic groups (1.21-1.65 in replication cohorts), and the score tracked worse cognition, more AD neuropathology, smaller hippocampi and abnormal CSF biomarkers. |
Association of an APOE-independent multi-ancestry polygenic risk score with AD, cognition, neuropathology, hippocampal volume and CSF biomarkers across ancestry groups | cohort study | not stated | The PRS was significantly associated with AD in European ancestry, African American, Caribbean Hispanic and Native American Hispanic groups with adjusted odds ratios between 1.14 and 1.52 per PRS standard deviation. PRS performance was validated in the replication cohorts (odds ratios: 1.21-1.65) |
Nature genetics
2026 ✓ Peer-reviewed PMID 42661068 |
| Polygenic risk / GWAS loci Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying the risk factors. Which factor mattered most differed by APOE risk group, on 2,065 cases split across 11 factors and three genetic strata, so the subgroup estimates are imprecise. |
Incident all-cause dementia over 12.4 years | cohort study | 182,473 | Low social contact HR 3.86 (95% CI 2.08-7.17) in low APOE risk group; less education PAF 11.35% in high APOE risk group |
Annals of Neurology
2025 ✓ Peer-reviewed PMID 41085200 |
| Polygenic risk / GWAS loci Genes (not modifiable) | Prevention |
Harm
whyDirection is for a higher integrative polygenic score: dementia hazard rose 1.15-fold per SD in older community-dwelling people independently of APOE, generalising to Europeans, East Asians and memory-clinic patients, and reaching five-fold risk when combined with APOE ε4 in memory-clinic patients. Not modifiable. |
Incident dementia by an integrative polygenic risk score (AD plus 23 vascular and neurodegenerative traits, excluding APOE) | cohort study | 241,935 | iPRS-DEM was associated with dementia risk independently of APOE in the elderly (subdistribution hazard ratio [sHR]per1SD = 1.15, 95% confidence interval [CI]: 1.03 to 1.28), which generalized to Europeans (EUR-sHRper1SD = 1.28, 95% CI: 1.09 to 1.51]), East-Asians (EAS-sHRper1SD = 5.29, 95% CI: 1.43 to 34.36), and memory-clinic participants (sHRper1SD = 1.25, 95% CI: 1.11 to 1.42) |
Alzheimer's & Dementia
2025 ✓ Peer-reviewed PMID 40042447 |
| Polygenic risk / GWAS loci Genes (not modifiable) | Prevention |
Harm
whyDirection is for a higher polygenic score: consistently associated with AD risk, age at onset and CSF biomarkers independently of APOE in Europeans and with AD risk in many other ancestries; a cross-ancestry score with the APOE region improved the association, and the signal weakened as the diagnosis was broadened. |
Association of a European-derived AD polygenic score with AD risk, age at onset and CSF biomarkers across 17 European countries and populations of other ancestries | cohort study | not stated | not established — pubmed abstract reports no numeric effect size. |
Nature genetics
2025 ✓ Peer-reviewed PMID 40533518 |
| Polygenic risk / GWAS loci Genes (not modifiable) | Prevention |
Harm
whyDirection is for a higher polygenic risk score: each SD raised the dementia hazard 1.35- to 1.42-fold after adjustment including APOE ε4, and the new scores modestly improved prediction (AUC 74.7% to 75.7-76.1%) while still explaining less risk than APOE. Not modifiable. |
Incident dementia (DSM-IV adjudicated) by polygenic risk score | cohort study | 12,031 | PRS-83SNP, PRS-SBayesR, and PRS-CS were associated with incident dementia, with fully adjusted (including apolipoprotein E [APOE] ε4) hazard ratios per standard deviation (SD) of 1.35 (1.23-1.47), 1.37 (1.25-1.50), and 1.42 (1.30-1.56), respectively. The AUC of a model containing conventional/non-genetic factors and APOE was 74.7%. This was improved to 75.7% (p = 0.007), 76% (p = 0.004), and 76.1% (p = 0.003) with addition of PRS-83SNP, PRS-SBayesR, and PRS-CS, respectively |
Alzheimer's & Dementia
2023 ✓ Peer-reviewed PMID 37177856 |
| Polygenic risk / GWAS loci Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying a higher genetic risk score: risk of AD rose 1.6- to 1.9-fold from the lowest to the highest decile, over and above age and APOE4. The main output is 75 risk loci, 42 new. |
Genome-wide risk loci and a genetic risk score for future AD/dementia | meta-analysis | 788,989 | We found 75 risk loci, of which 42 were new at the time of analysis ... The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele |
Nature Genetics
2022 ✓ Peer-reviewed PMID 35379992 |
| Rare protective or risk variant (APOE3 Christchurch, APOE R145C, RELN, FN1) Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying the African ancestry-specific APOE R145C variant with an ε3/ε4 genotype: three-fold higher odds of AD and onset about six years earlier in the discovery stage, replicated in stage 2 and concordant in stage 3. Not modifiable. |
Alzheimer's disease case status and age at onset among APOE ε3/ε4 carriers of African ancestry | case-control study | 31,929 | R145C was associated with an increased risk of AD (odds ratio [OR], 3.01; 95% CI, 1.87-4.85; P = 6.0 × 10-6) and was associated with a reported younger age at AD onset (β, -5.87 years; 95% CI, -8.35 to -3.4 years; P = 3.4 × 10-6) |
JAMA
2023 ✓ Peer-reviewed PMID 36809323 |
| TREM2 variants Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying TREM2 T96K: it increased AD risk in family-based and case-control sequencing data and, despite being a gain-of-function variant, impaired microglial clustering around plaques, amyloid uptake and the transition to disease-associated microglia in female 5xFAD mice. |
AD risk in a whole-genome sequencing dataset, and microglial plaque clustering, amyloid uptake and disease-associated transition in female 5xFAD knock-in mice | None | not stated | not established — pubmed abstract reports no numeric effect size (no odds ratio for the risk association is printed). |
Neuron
2026 ✓ Peer-reviewed PMID 41109213 |
| TREM2 variants Genes (not modifiable) | Prevention |
Harm
whyDirection is for carrying the risk variants: R62H and T96K caused excessive skipping of exon 2 and overproduction of a potentially antagonistic TREM2 isoform, and several early-onset dementia variants acted primarily through splicing defects. A molecular mechanism result, not a clinical outcome. |
TREM2 exon 2 skipping and isoform production in variant carriers | None | not stated | not established — pubmed abstract reports no numeric effect size. the library had recorded "1.8-fold increase in exon 2 skipping in r62h carriers", which the abstract… |
Brain
2024 ✓ Peer-reviewed PMID 38226698 |