The health benefits of physical activity are undeniable.
Yet, a recent study based on data published over the past 30 years challenges the famous adage Mens sana in corpore sano (a healthy mind in a healthy body) and questions the importance of exercise for both brain health and cognition.
A few days after that study was published, our team of health and neuroscience researchers released the results of our study of over a quarter million people. Our results clearly support the beneficial effects of both moderate and vigorous physical activity on cognitive functioning, fuelling an important scientific debate.
Who is right and who is wrong? Here’s what the science says.
Is physical exercise useless for cognitive functioning?
The first study was published on March 27, 2023. It is a review of 24 meta-analyses that re-examines data from 11,266 healthy people using a more rigorous approach.
Although almost all of the 24 meta-analyses included in this review concluded that exercise had a positive effect on cognitive function, the authors argue that the analyses performed were suboptimal. For example, they point out that both baseline levels of physical activity and the tendency of the scientific community to publish only significant results were rarely taken into consideration. Once these adjustments were made, the authors found results suggesting that the benefits of exercise are actually smaller than those estimated in the previous meta-analyses, and may even be negligible.
The second study, ours, is a genetic study involving nearly 350,000 people, published four days later, on March 31, 2023. Our results provide scientific evidence for the cognitive benefits of moderate and vigorous physical activity.
This evidence is based on the two-sample Mendelian randomization method, which takes advantage of the random variations in our DNA that occur at conception, before we are even born.
When any two humans are compared, 99.9 per cent of their genetic material is identical. DNA can be thought of as a long chain of building bricks, called nucleotides, that varies once every 1,000 bricks between these two humans. There are four types of randomly arranged bricks: thymine, adenine, guanine, and cytosine. Genetic variations can result in, for example, a cytosine brick in one place in one person’s DNA and a thymine brick in the same place in another.
The first sample in our study, consisting of 91,084 people, was used to identify genetic variations associated with differences in physical activity, as measured by wrist-worn motion sensors.
The second sample in our study, consisting of 257,854 people, was used to test whether the genetic variations associated with physical activity had a proportional effect on cognitive functioning. Since this was the case, we were able to conclude that there is a causal effect of physical activity on cognitive function.
Moderate exercise goes a long way
In our study, we show that physical activity improves cognitive functioning, but more importantly, that the effect of moderate physical activity (brisk walking, cycling) is 1.5 times greater than that of vigorous physical activity (running, playing basketball). This finding highlights that we do not need to push ourselves to the point of exhaustion to get cognitive benefits from exercise.
The cognitive benefits of moderate physical activity are 1.5 times greater than those of vigorous physical activity. (Shutterstock)
When all types of physical activity were considered together (including sedentary and light physical activity), our results no longer showed an effect on cognitive function. This finding confirms the importance of achieving at least moderate intensities to reap the cognitive benefits of physical activity.
Our results are consistent with those of a recent study that emphasizes the importance of exercise duration and intensity for the release of a protein called BDNF in the brain. This protein is involved in the creation of new neurons, new connections between these neurons, and new blood vessels to feed them.
This protein, whose production increases during exercise, is therefore one of the physiological mechanisms that explains the beneficial effects of physical activity on cognitive function. The very existence of this explanatory mechanism further strengthens the results supporting a beneficial effect of exercise on brain functioning.
It’s never too late to get started
Several differences may explain the discrepancy in results between the review of meta-analyses and our genetics-based study.
First, the review looks only at healthy people, which is not the case in our study. Second, our study distinguishes between light, moderate, and vigorous physical activity, whereas the review does not make this distinction. Finally, our genetic approach evaluates long-term effects, over a lifetime, whereas the review is based on interventions lasting between one month and two years.
As we are dealing with the temporal aspects of physical activity here, it is important to remember that it is never too late to start exercising. In fact, a 2019 study showed that starting to be active late in life has the same overall positive health effects as being active throughout life.
Conclusion: Hasty decisions are never good
Based on our findings, it appears that physical activity can still be considered beneficial for brain health and cognition. Moreover, in the current socio-political climate of mistrust of science, we should not jump to conclusions on the basis of a single study that contradicts years of research, yet is based on the very same data.
As is often the case in science, it is wiser not to make hasty decisions but to wait for additional studies before suggesting changes to physical activity guidelines. The accumulation of converging evidence from different research teams should be a prerequisite for changing public health messages. As this article shows, we are nowhere near that point, and the benefits of physical activity on a wide range of physical and mental health outcomes remain undeniable.
HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.
The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.
Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.
“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”
The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.
A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.
Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.
“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.
Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.
The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.
“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.
This report by The Canadian Press was first published Sept. 11, 2024.
ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.
Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.
Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.
Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.
The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.
“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.
Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.
Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.
Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.
A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.
This report by The Canadian Press was first published Sept. 10, 2024.
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