Television Viewing Time Linked to Higher Mortality From Pulmonary Embolism
A new study suggests spending too many hours each day in front of the television—behavior already associated with increased obesity and cardiovascular disease—may also increase the risk of dying from pulmonary embolism (PE).
Japanese researchers who prospectively followed individuals in the Japan Collaborative Cohort (JACC) Study for nearly 20 years saw a positive association between their self-reported TV-watching time and risk of mortality from PE, with a dose-response relationship evident with increasing hours spent glued to the set. The risk was doubled in those reporting more than 5 hours per day, for example, compared with those averaging less than 2.5 hours each day.
In a press release, lead author Toru Shirakawa, MD (Osaka University Graduate School of Medicine, Osaka, Japan), said the findings may have particular relevance for Americans, since studies indicate that adults in the United States watch more television than do Japanese adults.
Get Up and Put Down the Remote
The JACC Study enrolled 86,024 participants aged 40 to 79 years from 45 regions of Japan between 1988 and 1990. All participants completed a questionnaire about demographic characteristics, medical history, and lifestyle factors. In addition to asking about walking and sports activities, the lifestyle questions addressed the amount of time spent watching TV per day, which was categorized as fewer than 2.5 hours, 2.5 to 4.9 hours, or 5 or more hours.
A total of 59 deaths from PE were documented through the end of 2009, with a rate of 8.2 per 100,000 person-years among those watching television ≥ 5 hours per day. Although those reporting the most hours of TV had the highest risk, even those who watched for 2.5 to 4.9 hours per day had a 70% increased risk of dying from PE compared with those watching less than 2.5 hours. Furthermore, that risk increased by 40% for each additional 2 hours per day.
Publishing their results as a research letter in the July 26, 2016, issue of Circulation, Shirakawa and colleagues hypothesize that one potential mechanism behind the association may be development of venous stasis as a result of sitting for prolonged periods. Other risk factors such as obesity, hypertension, diabetes, and smoking did not show the same positive association with the risk of mortality from PE as did television viewing hours.
Similar to the advice given to travelers on long flights, the researchers suggest that viewers stand, stretch, and walk around after about an hour of TV watching, or tense and relax their leg muscles for 5 minutes while watching.
Plausible, Yet Not Definitive
In an interview with TCTMD, John A. Heit, MD (now retired from the Mayo Clinic, Rochester, MN), acknowledged it is “plausible” that prolonged sedentary TV watching could be associated with increased mortality from PE.
“However, in my opinion, this study does not prove that,” he said. “It is suggestive, but not confirmatory. That being said, I wouldn’t be surprised if another, better-designed study does show this to be true.”
One of the issues, Heit noted, is that the original study from which the cohort was drawn was actually designed to track cancer risk over time, not PE mortality. Additionally, participants filled out the questionnaire only once, leaving investigators with no other information about their cohort over the years except the death certificates that they obtained for those who died. But even those are “notoriously inaccurate” for assigning cause of death in general, and even more so in determining cause of death from PE without an autopsy, Heit observed.
“We have no idea what happened to these people over those 19 years,” he added. “All we have is the information they provided sometime between 1988 and 1990.” That is problematic, he explained, since lack of information on major risk factors that may have developed over the years is important for this type of study. Also important is the all-Japanese cohort, whose members have about 75% less risk of PE than people of European or African ancestry, Heit said, suggesting the risk may actually be somewhat underestimated.
Putting those caveats aside, however, he said the public health message is to be more active and spend less time in front of the tube. And, since the study was conducted before the modern era of computers and smart phones, more data are probably needed to see if those activities pose the same risk, he concluded.
- Shirakawa and Heit report no relevant conflicts of interest.
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Shirakawa T. Iso H, Yamagishi K, et al. Watching television and risk of mortality from pulmonary embolism among Japanese men and women: the JACC study (Japan Collaborative Cohort). Circulation. 2016;134:355-357.