By Elena Moro
The association between watching TV and development of dementia has been investigated in adults but results remain inconclusive. Some cross-sectional studies have associated TV viewing with worse cognition and increased risk of Alzheimer’s disease. Longitudinal studies, however, have shown more mixed results with some reporting no association while others reporting an association with poorer short-term memory and cognitive impairment.
This study’s main object was to evaluate the impact of watching TV on cognition six years later in adults ≥50 years old. Confounding factors such as sedentary behaviors, vascular risk factors, education and many others were considered. Moreover, the study aimed at identifying how many hours of TV viewing could be related to cognitive impairment in the long-term.
The authors analyzed data coming from the English Longitudinal Study of Ageing (ELSA), a longitudinal study of adults ≥50. Around 3,590 non-demented subjects at baseline were included (at Wave 4, 2008-2009) and followed up to six years (to Wave 7, 2014-2015). At baseline, the average age was 67.1 years (SD, 7.7; range, 52-90+), 56.3% were females, 72.3% were married or cohabiting, 98.5% were white, 14.8% working full time, 15.4% working part time, and the remaining no longer working. Of the total population, 19.6% were watching TV <2.5 hours per day, 19.1% 2.5-3 hours per day, 18.4% 3.5-4.5 hours per day, 23.4% 4.5-7 hours per day, and 19.6% >7 hours per day. Cognition was assessed using frequently used tests for immediate and delayed verbal memory and semantic fluency at baseline and follow-up.
Regression analysis using three statistical models was used to assess the association between watching TV and cognition, adjusting for baseline cognition, several demographic covariates (age, education, sex, ethnicity, employment status, social support), health-related covariates (depression, self-reported physical health, smoking, alcohol consumption and both long-standing and new chronic conditions including cardiovascular conditions) and sedentary behavior.
The authors found that watching TV for >3.5 hours per day was independently associated with worse verbal memory at six years compared to baseline. This association was also dose-dependent, i.e. longer TV watching was related to more affected memory. Worsening of semantic fluency at six years was also found to be related to TV watching for >3.5 hours per day but did not remain significant when adjusting for some of the demographic factors.
“This is an intriguing study”, says Prof. Antonio Daniele, Institute of Neurology, Catholic University, Rome, Italy. “Watching TV for more than 3.5 hours per day seems to have detrimental effects on cognitive processes involved in episodic verbal long-term memory, which is frequently affected in neurodegenerative disorders, including Alzheimer’s disease. Such effects were independent of demographic variables, health-related factors, physical activity, and sedentary behaviors different from TV watching. These detrimental effects of watching TV for more than 3.5 hours on episodic verbal memory might be explained by various mechanisms, namely the passive modality of processing visual and auditory information during TV viewing and, indirectly, by the reduction of time available for activities with beneficial effects on cognition (playing board games, reading, cultural activities). On the contrary, other more active screen-based activities (such as using internet and videogaming) may show beneficial effects on cognition. Moreover, it can be hypothesized that frequent TV viewing of stressful scenes (depicting violent or dramatic situations) might induced chronic stress, which may result over time in hippocampal atrophy and episodic memory impairment. Moreover, cognitive stress related to alert-passive interaction while watching TV, mostly related to violence, suspense or the specific representation of some graphic scenes, can have an indirect impact on cognition.”
“It is important to note that these findings support what has been known for a long time, that cognitive reserve, which seems to be protective to the brain comes from active learning. Watching TV is too passive to be considered learning.”, says Prof. Carmela Tartaglia, Division of Neurology, TWH, University of Toronto, Canada. “Spending time learning something new is time better spent than watching TV. The authors did not find that watching less than 3.5 hours of TV was associated with future risk of cognitive impairment, but it may still not be beneficial as it remains largely a passive activity. The study did not compare the effects of watching 3 hours of TV versus active learning. It remains to be seen whether TV viewing that consists of active learning is also associated with delayed cognitive impairment or if TV viewing in a more active manner i.e. in a group setting with active discussion can substitute for a learning activity. This study highlights that people need to be engaged and use their brains actively to ward off neurodegeneration.”
The other nominees for the May 2019 Paper of the month are:
- Zuluaga MI, Otero-Romero S, Rovira A, et al. Menarche, pregnancies, and breastfeeding do not modify long-term prognosis in multiple sclerosis. Neurology 2019;92:e1507-e1516. The authors assessed the relationship of age at menarche, the effects of pregnancy and breastfeeding with the risk of clinically defined MS and the Expanded Disability Status Scale. The analysis of data coming from a prospective cohort of 501 women with clinically isolated syndrome did not support any relationship of the variables with modifying the risk of clinically defined MS or disability.
- Onderwater GLJ, van Oosterhout WPJ, Schoonman GG, Ferrari MD, Terwindt GM. Alcoholic beverages as trigger factor and the effect of alcohol consumption behavior in patients with migraine. Eur J Neurol 2019;26:588-595. Data from a questionnaire administered to 2,197 patients with migraine in the Netherlands (LUMINA) found that alcohol could trigger migraine in around 35.6% of participants. In 77.8% of those subjects, red wine was the most common trigger with a rapid onset (<3 h) of migraine in 1/3 of patients. About 25% of patient with migraine had stopped consuming alcohol because of presumed trigger effect.
- Brott TG, Calvet D, Howard G, et al, on behalf of the Carotid Stenosis Trialists Collaboration. Long-term outcomes of stenting and endarterectomy for symptomatic carotid stenosis: a preplanned pooled analysis of individual patient data. Lancet Neurol 2019;18:348-356. Data from the four largest available randomized controlled trial evaluating the efficacy of carotid artery stenting (CAS) and carotid endoarterectomy (CEA) in a total of 4,775 patients with symptomatic carotid artery stenosis were analyzed to assess differences in the long-term outcome. No significant differences were found between the two procedures concerning the annual rates of ipsilateral stroke per person-year (median follow-up: 2-6.9 years)
- Alexandrov AV, Kohrman M, Soinne L, et al., for the CLOTBUST-ER Trial Investigators. Safety and efficacy of sonothrombolysis for acute ischaemic stroke: a multicenter, double-blind, phase 3, randomized controlled trial. Lancet Neurol 2019;18:338-347. The efficacy of a novel operator-independent transcranial ultrasound device delivering low-power high-frequency ultrasound in improving functional outcome was tested in patients with alteplase after acute ischemic stroke. Results coming from 355 patients who were randomized to have or not the ultrasound treatment did not show any impact on functional outcome at 3-month follow-up.
Prof. Elena Moro is Editor in Chief of EAN Pages and treasurer of EAN as well as Director of the Movement Disorders Center at the Centre Hospital Universitaire (CHU) of Grenoble, France and the Associate Director of the CHU Department of Psychiatry, Neurology and Rehabilitation.