The Bacillus Calmette-Guérin (BCG) vaccine, which provides protection against tuberculosis, can reduce the incidence of Alzheimer’s disease in patients with bladder cancer — and potentially provide new avenues to explore this effect in the general population, according to a recent study.
The study, “Bacillus Calmette-Guérin (BCG) therapy lowers the incidence of Alzheimer’s disease in bladder cancer patients,” was published in the journal PLOS One.
In addition to providing protection against tuberculosis, the BCG vaccine has also been used as a preventive treatment to reduce the recurrence of certain forms of bladder cancer. Although its exact mechanism of action is unknown, scientists believe BCG’s anticancer activity is linked to its ability to modulate the body’s immune system.
The immune system is known to play a major role in Alzheimer’s. Recent studies have proposed that the BCG vaccine may lower the prevalence of Alzheimer’s among the elderly by altering their immune system. This hypothesis was put forward based on past data showing an inverse relationship between BCG vaccination and the prevalence of Alzheimer’s or dementia.
“There’s data reaching back to the 1960s that shows that countries treating bladder cancer patients with the BCG vaccine had a lower prevalence of Alzheimer’s disease but it hadn’t been properly analyzed,” Hervé Bercovier, professor in microbiology and molecular genetics at the Hebrew University of Jerusalem and corresponding author of the study, said in a press release.
In the study, Bercovier and his team decided to put this hypothesis to the test by analyzing and comparing the incidence of Alzheimer’s in a group of elderly bladder cancer patients who received the BCG vaccine as part of their anti-cancer treatment and those who were not vaccinated.
The team followed up with 1,371 bladder cancer patients (1,134 males and 237 females), including 878 who received the BCG vaccine as an adjuvant treatment following tumor removal surgery. All patients were being treated at HU’s Hadassah Medical Center.
After a median post-operative follow-up period of eight years, 65 patients (4.7%) developed Alzheimer’s at a mean age of 84 years. From these, 21 (2.4%) had received BCG as part of their anti-cancer treatment, while the remaining 44 (8.9%) had not.
Statistical analyses also revealed that those who had never been treated with BCG had a more than four-times higher risk of developing Alzheimer’s than treated patients. This correlation held true irrespective of age and sex.
However, BCG vaccination was not found to reduce the prevalence of Parkinson’s disease among these patients (prevalence of 1.9% in BCG treated patients versus 1.6% in untreated patients).
“Our study is an important step towards understanding the ways in which our immune system is a major player in the pathogenesis [development] of Alzheimer’s and how the BCG vaccine, which modulates the immune system, may serve as an effective preventative treatment to this crippling condition,” Bercovier said.
“We hope that the results presented here will stimulate studies in other populations and further work on the mechanism of BCG protection,” the researchers wrote. “A prospective BCG vaccination study of elderly subjects can then be envisioned with different doses of BCG and a continuous follow-up of cognitive capacities.”
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