More than six million Americans suffer from Alzheimer’s disease or dementia, and that number is expected to grow significantly as the U.S. population ages. For decades, doctors across the globe have been looking for ways to strengthen aging brains and prevent dementia later in life. Researchers have tested a wide variety of treatments, including exercise, “brain games,” and medicine.
This week, researchers from the Minnesota Evidence-based Practice Center published a series of systematic reviews in the Annals of Internal Medicine that take a comprehensive look at the evidence on preventing and treating dementia. Unfortunately, they found some disappointing news: There is no convincing evidence that any of the treatments work.
To take a thorough look at the evidence, researchers identified randomized-controlled studies in four different treatment areas: cognitive training, prescription medicines, over-the-counter supplements, and vitamins and physical activity. They only included studies with low or medium risk bias, a measurement of the accuracy of the data, and studies that followed participants for at least six months. In each of the four areas, they pooled the data from the selected trials to look at the entire body of evidence.
For cognitive training, researchers identified 11 randomized-controlled trials. They found that healthy older adults who participated in cognitive training—think computer games that test different aspects of cognition, such as memory or processing speed—improved in the specific area participants were practicing but made no broader improvements in cognitive function. They found no credible evidence that this type of training prevents dementia.
A second systematic review looked at how well prescription medicines help to prevent or delay dementia. Researchers identified 51 different studies that tested six different types of medicine, including non-steroidal anti-inflammatory drugs, drugs for high blood pressure, and some hormones and drugs specifically formulated to treat dementia. The combined data found that none of these medicines help to prevent or delay dementia.
A third analysis reviewed the data on whether over-the-counter supplements or vitamins could help to prevent dementia. Thirty-eight different trials tested a wide range of supplements. The overall conclusion was that none of the supplements were beneficial in delaying or preventing dementia. But the research did link daily folic acid plus vitamin B12 with significant improvements on some memory tests. Unfortunately, it was not clear if those improvements were at all related to the overall prevention of dementia.
The fourth systematic review pooled data from 16 separate trials to measure whether physical activity helps to prevent cognitive decline. Researchers did not find sufficient evidence that aerobic training, resistance training, or tai chi helped to prevent dementia or improve cognition. They did find some evidence that a regimen combining exercise, diet, and cognitive training leads to cognitive improvements—promising results that may show that treating dementia requires a multi-faceted approach. At the conclusion of this review, researchers hypothesized based on the data that physical activity can be effective in preventing cognitive decline if it’s started early on and sustained, but adding in physical activity later in life may be less beneficial.
Part of the problem in truly understanding what contributes to and prevents dementia is the evidence available. While these new reviews only include studies that followed participants for at least six months, it is likely that decades of circumstances and choices—everything from diet and exercise to social life, profession, and hobbies—combine in a unique way to determine the cognitive health of each individual. Understanding these nuances would require conducting a study that spanned the course of decades and delved into many areas of participants’ lives.
While there is no conclusive evidence on the topic, there is a good chance that what is good for your overall health is good for your cognitive health. That means a well-balanced diet, regular physical activity, and social and intellectual stimulation are most likely your best bet in preventing or delaying dementia.