New research indicates that staying home and watching the idiot box has more dire implications than sitting through another rerun of Rocky IV.

How dire? It happens that watching too much television may increase your risk of developing Alzheimer’s/dementia and cause brain damage. Into the bargain, the negative effects of too much TV time could show up much sooner than previously thought, according to a recent Washington Post article.

A study from the Northern California Institute for Research and Education in San Francisco concerning the association between a sedentary lifestyle and the risk of developing dementia found that people who watch four hours or more of television per day scored significantly lower marks on tests measuring cognitive performance in middle age.

The study, which collected data on young adults and tracked them for the next 25 years, also determined that people who reported lower levels of physical activity scored lower on cognitive tests.

Implications for children and young adults are even more important, according to Kristine Yaffe, a professor of psychiatry, neurology, and epidemiology at the University of California in San Francisco. Because of their near constant attention to tablet devices, cell phones, and other digital media, this demographic group is at risk of a sedentary lifestyle both at home and in the workplace.

Yaffe also noted that the research can provide a message of hope: a more active lifestyle can lower the risk of later cognitive decline and possibly dementia. “This is something you can do something about,” she told reporters at the 2015 Alzheimer’s Association International Conference in Washington.

The California study examined 3,247 adults who were 18 to 30 years old when they enrolled in the Coronary Artery Risk Development in Young Adults Study. The study evaluated exercise and television-watching habits and their impact on cognitive function.

Study subjects reported on their television viewing and exercise habits on three questionnaires completed over the course of 25 years. The study defined low physical activity as burning fewer than 300 calories in a 50-minute session three times a week. Watching more than four hours of television per day was defined as a high amount. If study subjects maintained those levels on two of three follow-up visits, they were rated as having a long-term pattern of the behaviors.

Researchers noted that nearly 17 percent reported low physical activity, about 11 percent qualified as heavy TV viewers, and 3 percent reported both.

The study indicated a relatively sedentary person who engaged in minimal exercise and watched a high amount of television was two times more likely than an active peer to perform poorly on cognitive tests in midlife. Those results suggest a sedentary lifestyle in young adulthood may have an impact on the risk of developing dementia in later life.

Person watching TV on couch

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The study results are presented as shifting demographics are raising the median age of Alzheimer’s/dementia in the United States and several other developing countries. According to the Alzheimer’s Association, there are more than 5 million people living with Alzheimer’s/dementia now, but over 28 million baby boomers are projected to develop the disease by 2050. Projected costs will skyrocket from 2.1 percent of Medicare funding in 2020 to 24 percent by 2040.

Social Isolation Study Finds Similar Risks

A separate study had similar implications for the risks of social isolation and loneliness.

According to Nancy J. Donovan, an associate psychiatrist at Brigham and Women’s Hospital and Harvard Medical School, “the prevailing view is that loneliness is a form of psychosocial stress.”

In a study led by Donovan, 8,311 adults who were 65 or older were given biennial questionnaires designed to assess the perception of loneliness. The researchers rated the participants’ cognitive performance while factoring in health and sociodemographic status as well as the characteristics of their social network.

Donovan and her team found that the loneliest people—approximately 1 in 6—experienced the fastest decline in cognitive performance, with scores plummeting 20 percent faster than those who did not report feelings of loneliness.

Donovan said the study results stress the need to address the issue of social isolation among older adults.

“First, loneliness is a form of suffering in older people that is prevalent but undetected and untreated in medical practice,” she said. “Second, loneliness has consequences. Our work shows that loneliness, like depression, is associated with accelerated cognitive decline in older Americans. This finding is important because it opens up new approaches for preventing and treating Alzheimer’s disease.”