A study links a higher risk of dementia with a sedentary life in front of the television

Tracking hundreds of thousands of older people shows that those who watch more TV are more likely to have dementia.

However, the same does not happen if what they do is use the computer, a less passive mental behavior.

This research, which highlights the benefits of physical activity, shows that being sedentary is not bad for the brain in itself: it depends on what you do while sitting.

Science has accumulated enough evidence connecting mental health with physical activity, especially when cognitive decline looms with age.

In the same way, lack of exercise favors the appearance of coronary diseases among the most sedentary.

But the connection between sedentary lifestyle and dementia has not yet been categorically established.

Now, one of the largest studies to date looks at this relationship.

Researchers from several universities in the United States have compared the mental health status of 146,651 elderly people when they had an average age of 64.5 years with their situation a decade later.

In that time, 3,507 of them (about 2.5%) were diagnosed with dementia.

The study participants, obtained from an impressive public health tool (the British database UK Biobank) completed a series of questionnaires to know what their physical activity was and the time they spent sitting, either watching television or in front of the computer. (excluding working hours).

Sport and older

The results of the comparison, recently published in the scientific journal

, show that once other variables are controlled (sex, previous illnesses, smoking, work, age, etc.), physical activity appears to be related to a lower probability of developing any type of of dementia

The result confirms previous studies that have linked sport and mental health also in the elderly.

In April, for example, a study with several thousand Americans showed how physical exercise was related to a lower incidence of Alzheimer's.

But that research also mentioned performing demanding cognitive tasks as part of a diet for good brain aging.

The strong point of this new study is that it reveals a consistent relationship between sedentary lifestyle and mental health, but not just any sedentary lifestyle.

The questionnaires asked participants how many hours a day they spent watching television or in front of a computer screen.

What they have observed is that the longer you spend sitting in front of the television, the more likely you are to have dementia after a decade of follow-up.

The percentage of increased risk goes up to 40%.

But the same does not happen with computers: the probability of developing dementia in this case drops to 20%.

“It is possible that computer use during leisure time is cognitively demanding in a way that counteracts the risks of sitting too long”

David Raichlen, a researcher at the University of Southern California

David Raichlen researches the impact of physical activity on human health and well-being at the University of Southern California and is the lead author of the study published in

.

Raichlen points out that it is no longer worth condemning a sedentary lifestyle without differentiating what one is doing, even if one is sitting.

But he also acknowledges that it is not easy to know why the computer is better than television.

"We know that cognitive demand may have benefits for the brain, and it is possible that leisure-time computer use is cognitively demanding in a way that counteracts the risks of sitting too long," he says in an email.

To confirm this, adds Raichlen, "both a more detailed investigation of the mechanisms and the design of interventions to determine causal relationships" would be necessary, since his study "really can only detect associations."

The relationship between a sedentary lifestyle and lower energy consumption and muscle metabolism is evident, but it is not so easy to know how it affects cognitive deterioration beyond the metaphor of training the brain.

Neutralize the TV

A few weeks ago, neuroscientists from the German Center for Neurodegenerative Diseases published the partial results of a work still in progress.

They performed brain imaging on 2,500 people wearing an accelerometer to record their physical activity.

They found that those who performed more physical exercise tended to have a greater volume in critical areas such as the hippocampus, the memory control knob.

Although the sample included adults under 65 years of age, the protective cloak of sport was more marked in those over 70 years of age.

The researchers of this study also investigated the relationship between physical activity and sedentary lifestyle (television or computer).

They wanted to know if the former modulated or reduced the risk caused by the latter.

Taking as a reference the group of people with more physical activity and less time watching television, they saw a clear pattern in which those who spent more hours watching television had a higher risk of dementia, regardless of the intensity of physical exercise, although it decreased slightly in those who performed sports intensively.

"We see that physical activity reduces the risk of dementia, but it does not completely neutralize the risks associated with watching television," says Raichlen.

According to data from the World Health Organization, Alzheimer's and other dementias affect about 50 million people worldwide, about 5% of the world's elderly population.

Everything indicates that the figures will increase due to the increase in life expectancy and ageing.

The prevalence of the different types of dementia, almost testimonial among those under 60 years of age, rises with age and explodes among those who reach 85-90 years of age, a group in which half have mental problems.

Hence the urgency in determining whether or not there is a healthy sedentary lifestyle for the brain.

Different sedentary lifestyles

For neuropsychologist David Bartrés-Faz, professor at the University of Barcelona and associate researcher at the Guttmann Institute, Raichlen's research published in

seems very relevant.

"This is one of the largest samples following 60-year-olds without dementia for 12 years," says this expert in mental health and cognitive decline.

What is most important to him is the distinction between different ways of being sedentary.

“A sedentary lifestyle had been associated with cognitive decline and higher mortality, but now the relationship is not so clear,” he says.

However, what Bartrés-Faz most appreciates about the study is that the protective effect of physical exercise does not affect the risk of dementia from watching so much television.

“If you spend hours in front of the television, the risk is not reduced if you go to the gym for an hour afterwards.

It's okay to go to the gym, but you should also stop watching TV”, recalls the principal investigator of the Barcelona Brain Health Initiative.

However, Bartrés-Faz sees some limitations to the research.

The main one is that they did not carry out a baseline study of the cognitive status of each participant at the beginning of the investigation.

And that leads to the risk of reverse causality: "There is a possibility that those who watch more television had greater cognitive impairment or lower skills that make them choose a more passive activity, such as watching television," she highlights.

The researcher at the Barcelona Institute for Biomedical Research (IIBB-CSIC) Coral Sanfeliu is also pleased that one type of sedentary lifestyle is beginning to be differentiated from another, and sets a great example: “Even if you are at the other end of life, the school is sedentary”.

And she agrees with the authors of the research: “Being in front of the computer is not the same as being in front of the television.

Technological tools are already beginning to be taught in residences to combat cognitive deterioration”.

Ella sanfeliu ends the comparison with schoolchildren: “Children who do more physical activity improve school performance, concentration or their maturation process.

You have to combine both things, exercise and an active sedentary lifestyle.

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