TV watching habits in midlife could affect brain function

Long hours of television viewing in midlife may negatively impact grey matter volume and cognitive function, according to two analyses of participants in The Atherosclerosis Risk In Communities Neurocognitive Study (ARIC-NCS), presented at the American Heart Association Epidemiology, Prevention, Lifestyle & Cardiometabolic Health Conference (EPI 2021).

“Our findings suggest that the amount of television viewing, a type of sedentary behaviour, may be related to cognitive decline and imaging markers of brain health. Therefore, reducing sedentary behaviours, such as television viewing, may be an important lifestyle modification target to support optimal brain health,” said Assistant Professor Priya Palta from the Columbia University Vagelos College of Physicians and Surgeons, New York City, New York, US, lead author of one of the studies.

In the first analysis, 1,601 individuals enrolled in ARIC (mean age 76.2 years, 60.5 percent female, 27.2 percent Black) reported their television viewing habits in midlife at two study assessments (visit 1 [1987–1989] and visit 3 [1993–1995]) and underwent brain MRI at visit 5 (2011–2013). Television viewing habits were categorized as low (never/seldom), medium (sometimes), or high (often/very often).

At visit 3, compared with participants with low television viewing levels (n=288), those with medium or high viewing levels (n=782 and 531, respectively) did not have an increased risk of cerebrovascular lesions (ie, cortical infarcts, lacunar infarcts, or subcortical microhaemorrhage; p_trend=0.976, 0.361, and 0.741, respectively). [EPI 2021, abstract MP24]

There was also no significant difference pertaining to white matter microstructural integrity and white matter disease (ie, mean fractional anisotropy, mean diffusivity, or log white matter hyperintensity volume; p_trend=0.403, 0.517, and 0.615, respectively) or total cortical or temporal lobe meta regions of interest (p_trend=0.726 and 0.612, respectively). However, deep grey matter levels were significantly lower in participants with medium and high vs low levels of viewing (β, -0.14 and -0.16; p_trend=0.004).

A total of 971 participants had persistent television viewing habits, which was defined as the same frequency of television viewing at visits 1 and 3.

The results were similar to those at visit 3, with a significant reduction in deep grey matter levels among participants with persistent medium and persistent high vs persistent low levels of television viewing (β, -0.16 and -0.17; p_trend=0.029).

“Compared to low television viewing, medium and high television viewing in midlife was significantly associated with smaller deep grey matter volumes in late-life after multivariable adjustment* [with the] associations stronger for persistent television viewing,” said study lead author Professor Kelley Pettee Gabriel from the University of Alabama, Birmingham, Alabama, US, and co-authors.

TV viewing up, cognition down?

A second study involving 10,700 ARIC participants (mean age 59 years, 44 percent male, 19 percent Black) suggested that high levels of television viewing may impact cognitive decline. [EPI 2021, abstract P149]

Television viewing habits were self-reported at visits 1 and 3 (1987–1989 and 1993–1995, respectively) and cognitive tests of working memory, language, and executive function were administered at visits 4 (1996–1998) and 5 (2011–2013). A total of 6,462 participants met the criteria for persistent television viewing.

The participants were followed up over a median 17.4 years during which time 1,063 cases of dementia occurred.

While high levels of television viewing were initially associated with an increased risk of dementia compared with low levels (hazard ratio [HR], 1.42), the risk was attenuated in the multivariable adjusted analysis (HR, 1.09).

Global cognition declined more quickly among participants with high and medium vs low levels of television viewing (-0.04 for both vs low), particularly among those with persistent high vs persistent low viewing levels (-0.06).

There was a 6.9 percent greater decline in cognitive function over 15 years among participants with high or medium vs low levels of television viewing.

“Television viewing, a proxy [measure for] sedentary behaviour, is associated with cognitive decline, but not incident dementia,” said Palta and co-authors.

Sedentary behaviour: A marker of brain health

“While studies have shown the benefits of exercise to support brain health, less is known about the potential consequences of prolonged sedentary behaviour such as television viewing on brain structure and function. This is important to look at because other studies have shown that physical activity and sedentary behaviours may have different effects on health and disease,” Gabriel pointed out.

“Engaging in healthy behaviours during midlife, between ages 45 to 64 years in the context of our study, may be important factors to support a healthy brain later in life,” she added.

The authors encouraged further research into analysing the effect of accumulated, and different types of, daily sedentary behaviours on brain markers and cognitive and dementia outcomes.