Cognitive Decline and Cancer Again Inversely Linked

Megan Brooks

April 10, 2014

A population-based study from Spain shows an inverse association between cognitive decline and cancer.

In a group of elderly individuals without dementia at baseline, faster cognitive decline was associated with a lower risk of dying of cancer over more than a decade.

Prior studies have suggested that people with Alzheimer's disease, Parkinson's disease, and Huntington's disease are less likely to develop cancer, the authors note in their article.

But a "major problem with epidemiologic studies that have reported an inverse association between Alzheimer's disease and cancer is the very likely underdiagnosis of cancer once dementia has been diagnosed," Julián Benito-León, MD, PhD, from University Hospital "12 of October" in Madrid, Spain, told Medscape Medical News.

"The results of the current study suggest that elderly people without dementia with faster cognitive decline are at reduced risk of mortality from malignant neoplasm. Indeed, the current study gives credibility to the inverse association of both conditions, recognized in other studies, since there was no possibility of underdiagnosis of cancer because the subjects with a faster cognitive decline were still nondemented," he explained.

The study was published online April 9 in Neurology.

Building Credibility

The study involved 2627 community-dwelling adults age 65 and older without dementia at baseline who were enrolled in the Neurological Disorders in Central Spain (NEDICES) study.

Participants took a 37-item version of the Mini-Mental State Examination (37-MMSE) at baseline and roughly 3 years later. They were divided into tertiles based on change in 37-MMSE score: Those whose scores were declining the fastest were in the higher tertile (defined as at least a 2-point decline in score), and those whose scores on the tests improved were in the lower tertile (defined as at least a 2-point improvement in score).

During a median follow-up of 12.9 years, 1003 participants died (38.2%), including 339 (33.8%) in the higher tertile (faster cognitive decline) and 664 (66.2%) in the lower and middle tertiles.

Cancer was reported significantly less often in those in the higher vs middle/lower tertile of MMSE change (20.6% vs 28.6%), the researchers say.

In a Cox model adjusting for a variety of relevant factors, including smoking, diabetes, and heart disease, those in the higher tertile of cognitive decline were 30% less likely to die of cancer (hazard ratio, 0.70; P = .02) than their peers in the lower/middle tertiles.

"As yet undiscovered mechanisms may either promote a neurodegenerative process (uncontrolled cellular destruction) or annul other conditions, namely, cancer (uncontrolled cellular proliferation)," the authors note in their article.

"Both cancer and neurodegenerative disorders are characterized by a disarrangement of cell-regulation mechanisms, with increased cell survival and proliferation in the former and with increased cell death in the latter process," they point out.

"We need to understand better the relationship between a disease that causes abnormal cell death and one that causes abnormal cell growth," Dr. Benito-León added in a statement. "With the increasing number of people with both dementia and cancer, understanding this association could help us better understand and treat both diseases."

The study was supported by the Spanish Health Research Agency, the Spanish Office of Science and Technology, the National Institutes of Health, and the European Commission. The authors have disclosed no relevant financial relationships.

Neurology. Published online April 9, 2014. Abstract

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