Prolonged TV Watching Increases Blood Clot Risk by a Third

Dr Rob Hicks

January 21, 2022

For many years it has been accepted that inactivity post-operatively or during long-haul travel increases the risk of venous thrombo-embolism (VTE). More than 10 years ago, stories of people suffering venous thrombosis as a consequence of playing computer and video games for long periods of time, colloquially known as ‘Gamer’s thrombosis’, appeared in the news.

Now researchers from University of Bristol have added binge-watching TV to the list of potential VTE risk-factors, at a time when lockdown has made box-set and online streaming binge viewing increasingly popular.

Prolonged Viewing (4+ Hours/Day)

For the study, published in the European Journal of Preventive Cardiology, the researchers set out to determine whether TV viewing is associated with a greater risk of venous thrombo-embolism. To do this they performed a systematic review and meta-analysis of all published observational cohort subjects examining this subject.

Three studies – two from the USA and one from Japan – were identified for inclusion and had been published between 2016 and 2021. The studies comprised 131,421 participants whose average age was 54-65 years. TV viewing time was assessed in all studies through self-reported questionnaires, with participants being categorised as ‘prolonged viewers’ if they watched TV at least 4 hours a day, and ‘never/seldom viewers’ if they watched less than 2.5 hours a day.

All three studies adjusted for established risk factors such as age, sex, body mass index, and physical activity. Lead author Dr Setor Kunutsor, of the University of Bristol, said: "All three studies adjusted for these factors since they are strongly related to the risk of VTE; for instance, older age, higher BMI and physical inactivity are linked with an increased risk of VTE."

During the follow-up period – the average duration of which ranged from 5.1 years to 19.8 years - 964 participants developed VTE.

Risk Increased Regardless of Other Factors

Their analysis identified that prolonged viewers were 1.35 times more likely to develop VTE compared to never/seldom viewers.

"In pooled analysis of three cohort studies, prolonged TV viewing was associated with an increased VTE risk, which was regardless of physical activity," the authors said.

"The findings indicate that, regardless of physical activity, your BMI, how old you are, and your gender, watching many hours of television is a risky activity with regards to developing blood clots," said Dr Kunutsor.

The authors suggested a number of reasons why prolonged TV viewing may increase VTE development, for example, by increasing systemic inflammation, plasma viscosity, and platelet aggregation. Also the increase in risk factors such as body weight, hypertension, and lipids, as a consequence of binge-watchers tending to eat unhealthy snacks Dr Kunutsor pointed out.

The authors highlight there are a number of limitations to the study, including the limited number of studies available to analyse, as well as the wide variability in categorisation of TV viewing time and definition of prolonged TV viewing. Dr Kunutsor emphasised that the findings are based on observational studies and do not prove that extended TV watching causes blood clots.

They concluded that their research may support an association between prolonged TV viewing and increased risk of VTE, with Dr Kunutsor saying: "Our study findings also suggested that being physically active does not eliminate the increased risk of blood clots associated with prolonged TV watching." 

He added that people should limit time spent watching television, and that "long periods of TV watching should be interspersed with movement to keep the circulation going. And avoid combining television with unhealthy snacking".

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