Alzheimer Disease <-> Cancer

name: com_Alzheimer_Disease__Cancer
creation_date: "2026-07-03T14:04:34Z"
curation_status: CURATED
notes: >-
  The cancer/Alzheimer's-disease "inverse correlation" (or "cancer-AD paradox"):
  a history of cancer is associated with a reduced subsequent risk of Alzheimer's
  disease, and a diagnosis of Alzheimer's disease is associated with a reduced
  subsequent risk of cancer. This is a reciprocal (bidirectional) PROTECTIVE
  association, curated here as the flagship inverse comorbidity. Two features
  distinguish it from an artifact and from generic neurodegeneration. First, the
  major methodological biases (competing risk of death, diagnostic bias,
  selective survival) have been evaluated and are judged unlikely to fully
  explain the association (Ospina-Romero 2020), and the pattern is corroborated
  at the neuropathological level - a prior cancer diagnosis is associated with a
  lower burden of Alzheimer's-type neuropathology (Karanth 2022). Second, the
  inverse association appears relatively specific to Alzheimer's disease: it is
  seen for AD but not for vascular dementia (Roe 2010). Mechanistically this is
  framed as an evolutionary trade-off in which shared aging pathways are driven
  in opposite directions (cancer = sustained proliferation / growth-suppressor
  evasion / immune evasion; AD = excess neuronal death / growth-suppressor
  activation / immune activation), with AD-specific effectors such as APP and
  amyloid-beta acting as tumour suppressors. The antagonistic-pleiotropy
  substrate is captured by the `cellular_senescence` (deleterious arm) and
  `senescence_tumor_suppression` (tumour-suppressive arm) mechanism modules; the
  aging-associated loss of stemness node of the latter (PMID:39633048) is one
  conserved arm by which aging biology suppresses tumour initiation. Curation of
  this entry was prompted by the Comment "The cancer Alzheimer's disease paradox"
  (Feng, npj Aging 2026;12:93, doi:10.1038/s41514-026-00442-1). Note that the
  relationship is NOT uniformly protective across all neurodegeneration: cancer
  and Parkinson's disease show a more complex pattern (inverse for most cancers
  but a positive association with melanoma), which would be curated separately as
  effect_direction: MIXED.

disease_a:
  slug: Alzheimer_Disease
  preferred_term: Alzheimer disease
  term:
    id: MONDO:0004975
    label: Alzheimer disease

disease_b:
  slug: Cancer
  preferred_term: cancer
  term:
    id: MONDO:0004992
    label: cancer

directionality: BIDIRECTIONAL
effect_direction: PROTECTIVE

literature_evidence:
- reference: PMID:33185677
  supports: SUPPORT
  evidence_source: HUMAN_CLINICAL
  snippet: "Observational studies consistently report inverse associations between cancer and Alzheimer disease (AD)."
  explanation: >-
    Systematic review and meta-analysis (22 studies, 9,630,435 individuals)
    establishing the consistently reported inverse (protective) association
    between cancer and Alzheimer's disease.
- reference: PMID:33185677
  supports: SUPPORT
  evidence_source: HUMAN_CLINICAL
  snippet: "cancer was associated with decreased AD incidence (cohort studies: random-effects hazard ratio, 0.89; 95% CI, 0.79-1.00; case-control studies: random-effects odds ratio, 0.75; 95% CI, 0.61-0.93)."
  explanation: >-
    Pooled effect estimates below 1 quantify the protective direction: a prior
    cancer diagnosis is associated with lower Alzheimer's disease incidence.
- reference: PMID:33185677
  supports: SUPPORT
  evidence_source: HUMAN_CLINICAL
  snippet: "Studies with insufficient or inappropriate confounder control or greater likelihood of AD diagnostic bias had mean hazard ratios closer to the null value, indicating that these biases could not explain the observed inverse association."
  explanation: >-
    Bias-adjusted metaregression argues the inverse association is not merely an
    artifact of confounding or diagnostic bias, supporting a genuine protective
    relationship.
- reference: PMID:22411920
  supports: SUPPORT
  evidence_source: HUMAN_CLINICAL
  snippet: "Cancer survivors had a lower risk of Alzheimer's disease than those without cancer, and patients with Alzheimer's disease had a lower risk of incident cancer."
  explanation: >-
    Framingham Heart Study prospective cohort plus nested case-control analysis
    demonstrating the reciprocal (bidirectional) protective association in both
    directions.
- reference: PMID:20032288
  supports: SUPPORT
  evidence_source: HUMAN_CLINICAL
  snippet: "prevalent Alzheimer disease (AD) was longitudinally associated with a reduced risk of cancer, and a history of cancer was associated with a reduced risk of AD"
  explanation: >-
    Cardiovascular Health Study cohort independently confirming the reciprocal
    protective association between Alzheimer's disease and cancer.
- reference: PMID:20032288
  supports: SUPPORT
  evidence_source: HUMAN_CLINICAL
  snippet: "No significant association was found between cancer and subsequent development of VaD."
  explanation: >-
    Specificity evidence: the inverse association holds for Alzheimer's disease
    but not for vascular dementia, arguing the effect is AD-specific rather than
    a generic dementia/neurodegeneration phenomenon.
- reference: PMID:35094057
  supports: SUPPORT
  evidence_source: HUMAN_CLINICAL
  snippet: "Cancer diagnosis was associated with a lower burden of Alzheimer's disease pathology and less cognitive impairment. These findings from a community-based cohort with neuropathological confirmation of substrates support the hypothesis that there is an inverse relationship between cancer and Alzheimer's disease."
  explanation: >-
    Autopsy cohort (University of Kentucky ADRC linked to the Kentucky Cancer
    Registry) providing neuropathological corroboration: prior cancer is
    associated with a lower burden of Alzheimer's-type pathology and cognitive
    impairment.

hypotheses:
- description: >-
    Tumour-suppressive amyloid/APP arm. Beyond the epidemiology, Alzheimer's
    disease-specific effectors provide a candidate mechanism for the protective
    direction: amyloid-beta (Abeta) and its precursor APP have tumour-suppressive
    and anti-angiogenic activity. Amyloid-beta oligomers inhibit the proliferation
    of human cancer cell lines in vitro, and transgenic mouse models of AD that
    overproduce Abeta show impaired growth and vascularization of implanted
    tumours - i.e., the AD-like, Abeta-rich brain environment is hostile to
    tumour growth. This is the AD-specific complement to the conserved
    aging/senescence tumour-suppressive barrier captured by the
    `senescence_tumor_suppression` module, and together they frame the cancer-AD
    inverse correlation as an antagonistic-pleiotropy trade-off in shared aging
    pathways rather than two independent phenomena.
  evidence:
  - reference: PMID:31509551
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The effect of the cell growth inhibition, which was stronger in the case of HFIP Aβ oligomers, was observed for all cell lines."
    explanation: >-
      In vitro evidence that amyloid-beta oligomers inhibit growth across
      multiple human cancer cell lines (leukemia, lung, breast), supporting a
      direct tumour-suppressive activity of an AD-defining molecule.
  - reference: PMID:20739545
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our data reveal that intracranial tumor growth and angiogenesis is significantly reduced in Tg APPsw and Tg PS1/APPsw mice compared with their wild-type littermates."
    explanation: >-
      In vivo model-organism evidence that an Abeta-overproducing, AD-like brain
      environment suppresses orthotopic glioma growth and angiogenesis,
      supporting the protective direction at the tissue level. Model-organism
      evidence is kept distinct from the human epidemiological evidence above.