WAs we get older, diseases come. Cancer and Alzheimer’s dementia are among the most common and most feared health conditions, especially in an aging country like the UK. Decades ago, researchers at the New York Psychiatric Center observed a strange relationship between these two diseases. During autopsythey found an inverse relationship between cancer and Alzheimer’s disease.
In one of the first epidemiological studies on this topic, Jane Driver of Brigham and Women’s Hospital in Boston, Massachusetts, USA, followed 1,278 participants aged 65 and older for an average of 10 years. Published in 2012The results showed that cancer survivors had a 33% lower risk of later developing Alzheimer’s disease than people without a history of cancer.
While the findings were interesting, the scientific community urged caution and pointed out potential pitfalls when dealing with age-related diseases. One of them concerned so-called survivorship bias. Perhaps people with a history of cancer simply don’t live long enough to develop Alzheimer’s disease.
Since then, scientists around the world have analyzed the relationship between cancer and Alzheimer’s disease in more detail, building an increasingly convincing evidence base. in Biggest study everResearchers from Imperial College London, published in July this year, provide compelling evidence that the incidence of dementia following a cancer diagnosis is low. They looked at NHS health data for more than 3 million people aged 60 and over, followed for an average of 9.3 years, taking great care to correct for potential bias. Their results show that cancer survivors have a 25% lower risk of developing age-related dementia compared to people without a history of cancer. An inverse association was observed for the most common types of cancer, including prostate, colon, lung, and breast.
“The relationship between cancer and Alzheimer’s disease is very interesting and deep-rooted,” said Erin Abner, a professor at the University of Kentucky. “Many people have questioned this result and tried hard to find other explanations for the inverse association, but even after accounting for confounders, the inverse association continues to emerge.”
Two years ago, Abner announced: clinical evidence In case of inverse correlation. Unlike previous epidemiological studies, she examined brain autopsies of patients at the university’s Alzheimer’s Disease Research Center. “We found a fairly consistent association between people with cancer and reduced levels of amyloid in the brain, which is a hallmark of Alzheimer’s disease,” she says.
In her study, the inverse association was found only in Alzheimer’s disease and not in dementia in general. In contrast, many previous epidemiological studies did not distinguish between Alzheimer’s disease and other age-related dementias. However, the majority of elderly patients with dementia have Alzheimer’s disease.
But that’s not all. The reverse relationship has another twist. Not only do people with a history of cancer have a lower risk of dementia, but people with Alzheimer’s disease are less likely to develop cancer. In a 2012 study, Jane Driver reported that the inverse relationship exists in both directions. recreated in northern Italy It has surveyed more than 1 million residents, and recent surveys have also been conducted in South Korea. According to this researchPatients with Alzheimer’s disease have been shown to be 37% less likely to develop malignancies overall compared to patients without dementia. Again, this finding was met with skepticism. Perhaps, critics argue, people with dementia are less likely to be screened for cancer, given the potentially limited effectiveness of therapy.
“The results have been replicated many times, and most experts in the field now believe that this inverse relationship is real,” said Dr. Elio Rivoli, who confirmed it, said: “The next step is to understand the biology behind this phenomenon.”
Some researchers have suggested that cancer treatment itself may influence the risk of dementia. In recent years, inflammation has emerged as a central process in the onset and progression of Alzheimer’s disease, so chemotherapy may protect neurons by suppressing inflammation.
But for Elio Rivoli, that’s not all. The fact that the inverse relationship is bidirectional suggests that there may be underlying biological mechanisms that influence the two groups of diseases in opposite directions. Researchers at Imperial College conducted a genetic analysis. “After examining hundreds of genes, we identified a genetic profile that predicted increased risk of cancer, and found that this profile was associated with decreased risk of dementia.”
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According to Riboli, certain genetic factors may be involved in tissue regeneration. “Growth factors are a large family of molecules that regulate tissue regeneration and growth. They are commonly associated with improved cardiovascular health,” he says. “Having a genetic structure that favors replication may promote tissue and artery regeneration, but it may also slightly increase the risk of some cancers.”
The surprising discovery could open up new areas of research, Rivoli said. For example, it has long been known that people with diabetes have an increased risk of developing cancer. One notable exception: Men with diabetes have a 10-20% reduced risk of developing prostate cancer. “Why does having diabetes reduce the risk of prostate cancer? For prostate cancer, we are desperately trying to understand the risk factors,” Rivoli asks. Similarly, research into the inverse relationship between cancer and dementia may reveal new molecular pathways that contribute to or protect people from developing dementia. “You open the window and suddenly you see a new horizon,” he says.
Cancer is associated with uncontrolled cell growth, while dementia is associated with excessive nerve cell death. Mikyung Park of the Korea Institute of Science and Technology in Seoul, South Korea, recently said, review Elucidation of molecular mechanisms that act inversely in cancer and neurodegeneration. Some lead to increased resistance to cell death, while others lead to an increased risk of cell death. Dysfunction of mitochondria, the powerhouses of cells, may provide an important link between cancer and neurodegeneration. hypothesis advocate It was written ten years ago by Jane Driver and Lloyd Demetrius, based on mathematical arguments.
Understanding the inverse relationship between cancer and neurodegenerative diseases may ultimately help treat or prevent these common conditions. However, many questions remain unanswered. “Cancer and dementia are actually different diseases,” says Erin Abner. “We don’t have the granular data to draw strong conclusions about specific types of disease.” Furthermore, in both cancer and Alzheimer’s disease, between the onset of the disease and the onset of symptoms, has a long latent period, raising questions about the timing of this inverse relationship.
These mysterious discoveries have no practical relevance so far. “But even now, for cancer survivors, it may be a small consolation that things will be a little easier in the future,” Abner says.
