In an evolving health landscape, emerging research continues to highlight concerns that could impact everyday wellbeing. Here’s the key update you should know about:
New research shows that watching over 4 hours of TV daily increases the risk of cognitive impairment and may be linked to dementia, highlighting a major public health concern.
Study: Television watching and cognitive outcomes in adults and older adults: A systematic review and dose-response meta-analysis of observational studies. Image credit: Proxima Studio/Shutterstock.com
A recent systematic review and meta-analysis published in PLOS ONE claims that prolonged television watching can impair cognitive functions in adults and older adults.
Background
Advances in medical science have extended human lifespan, but this has also led to a rise in disability and age-related disorders. Dementia is one such age-related condition, characterized by reduced cognitive functioning and associated functional impairment.
Globally, dementia is the seventh leading cause of death and a major contributor to disability in older adults. The number of people living with dementia is projected to increase from 55 million in 2019 to 139 million in 2050.
Alzheimer’s disease is the most common form of dementia. It is characterized by progressive declines in episodic memory and executive functions, often leading to memory loss and spatial disorientation. While some treatments can slow disease progression, there is currently no cure for this condition. As a result, identifying factors that influence Alzheimer’s onset and developing interventions to reduce risk are the most effective approaches to addressing the global dementia burden.
Watching television is one of the most common daily leisure activities among adults and older adults. The amount of time spent watching television is also a marker of sedentary behavior. Existing evidence suggests that prolonged television watching is associated with increased risk of obesity, diabetes, and cardiovascular disease.
Studies investigating the impact of television watching on cognition have reported both positive and negative effects. These discrepancies may partly be due to the differences in study design and methodological aspects.
Considering these inconsistent findings, the current systematic review and meta-analysis were designed to comprehensively understand whether there is any relationship between television watching and cognitive functions in adults and older adults.
The systematic review included 35 studies with 1,292,052 participants, of which 28 studies were further meta-analyzed.
Key findings
The dose-response meta-analysis of selected studies revealed that longer durations of television watching are associated with a significantly higher risk of cognitive impairment in adults and older adults. The risk was more pronounced for more than four hours a day.
Specifically, the meta-analysis revealed that watching television for an average of six hours daily is associated with a significantly lower cognitive score.
The risk of bias analysis, or the quality analysis, of selected studies indicated that the dose–response meta-analysis of cognitive impairment risk has a moderate level of certainty, whereas the dose–response meta-analysis of cognitive score has a low level of certainty.
Significance
This systematic review and dose-response meta-analysis reveal that watching television for more than four hours a day can significantly increase the risk of cognitive impairment, and that watching television for more than six hours a day can significantly reduce cognitive scores in adults and older adults.
Notably, the conventional meta-analysis findings were mixed. While the dose-response results were significant, the overall conventional meta-analysis for cognitive impairment was null. However, one included study indicated that a longer duration of television watching is associated with a significantly higher risk of Alzheimer’s disease. The authors caution that this finding requires further validation.
Existing evidence links longer television watching to reduced brain volume in several brain regions associated with language, memory, and communication. The paper notes that these findings are suggestive rather than conclusive and may persist even after accounting for lifestyle factors such as physical activity. These brain regions are usually affected by dementia. Residual confounding, however, cannot be ruled out.
Prolonged television watching increases sedentary behavior, a known risk factor for cognitive impairment. Furthermore, prolonged television watching has been linked to increased risks of obesity and diabetes, as well as poor psychosocial outcomes, such as loneliness, depression, and low life satisfaction. The authors suggest that these indirect effects may collectively contribute to dementia risk.
The current findings raise a major public health concern, as the literature reports that adults spend more than seven hours a day watching television. With the increasing global prevalence of dementia, these findings highlight the need for increasing public awareness about the cognitive disadvantages of watching television for prolonged periods and encouraging people to look for alternative leisure activities that will improve cognitive performance and overall quality of life.
This systematic review and meta-analysis included only observational studies; therefore, the causality of the observed associations could not be determined. Moreover, some of the analyzed findings have a low or very low level of certainty. These findings should be interpreted with caution.
The studies included in the meta-analysis involved only adults and older adults, which restricts the generalizability of the findings to younger populations. Further research is needed to establish the causal association between television watching and risk of cognitive impairment, as well as the potential influence of confounding factors on this association.