Association of cancer and Alzheimer's disease risk in a national cohort of veterans

Abstract

INTRODUCTION To examine the risk of AD among cancer survivors in a national database. METHODS Retrospective cohort of 3,499,378 mostly male US veterans ≥65 followed 1996–2011. We used Cox models to estimate risk of AD and alternative outcomes (non-AD dementia, osteoarthritis, stroke and macular degeneration) in veterans with and without a history of cancer. RESULTS Survivors of a wide variety of cancers had modestly lower AD risk, but increased risk of the alternative outcomes. Survivors of screened cancers, including prostate cancer, had a slightly increased AD risk. Cancer treatment was independently associated with decreased AD risk; those who received chemotherapy had a lower risk than those who did not. DISCUSSION Survivors of some cancers have a lower risk of AD but not other age-related conditions, arguing that lower AD diagnosis is not simply due to bias. Cancer treatment may be associated with decreased risk of AD.

Cancer and dementia: Two sides of the same coin?

“…Interestingly, multiple studies suggest an inverse association between cancer and dementia, in particular for Alzheimer disease (AD) . In 1990, Yamada et al investigated risk factors for dementia in atomic‐bomb survivors and observed that the odds of having cancer prior to AD was 70% lower in patients with AD compared to persons without AD.…”

“…Few studies investigated the relation of cancer with other diseases including stroke, automobile injuries, osteoarthritis and macular degeneration, which were used as negative control diseases . In case of survival bias, cancer patients would also have a decreased risk of these diseases.…”

“…Furthermore, several studies investigated the risk of dementia in relation to different cancer sites or stages . Tumours originated deep in the body may progress over a longer time until they become clinically manifest, compared to tumours located at the body surface.…”

“…Ou et al found that the risk of cancer in patients with AD within the first year after AD diagnosis was comparable to the cancer risk in the general population, whereas the risk was lower thereafter (standardised incidence ratio (SIR) 0.98, 95% CI 0.76‐0.95 and 0.85, 95% CI 0.76‐0.95, respectively). In addition, Frain et al determined the risk of AD during four time periods after cancer diagnosis for different cancer types, which was relatively constant over time depending on cancer type.…”

Midlife cancer/diabetes and risk of dementia and mild cognitive impairment: A population‐based prospective cohort study in Japan

“…While diabetes is a known modifiable risk factor for both dementia and cancer, the association between cancer and dementia remains uncertain. Population‐based cohort studies have reported inconsistent risk levels for dementia among individuals with cancer . We therefore conducted a cross‐sectional survey using a prospective Japanese cohort to examine whether having cancer or comorbid cancer and diabetes from midlife increases the risk of physician‐diagnosed dementia.…”