LONDON – Middle-aged adults who watch TV for an average of 5 or more hours per night face an adjusted 6.5-fold increased risk of fatal pulmonary embolism, compared with those who watch less than 2.5 hours per night, Toru Shirakawa reported at the annual congress of the European Society of Cardiology.
This was the key lesson gleaned from an analysis from the Japan Collaborative Cohort Study, the first large-scale prospective investigation of the relationship between prolonged television watching and pulmonary embolism (PE). The study included 86,024 Japanese participants aged 40-79 years prospectively followed for a median of 18.4 years, explained Mr. Shirakawa, a medical student at Osaka (Japan) University.
Toru Shirakawa
And while many busy medical professionals might presume 5 hours–plus of TV watching per night constitutes extreme behavior, that’s hardly the case. Indeed, according to the Nielsen survey, American adults watch an average of 4.85 hours of TV nightly.
During the study period there were 59 confirmed deaths from PE. In a multivariate analysis adjusted for sex and baseline age, cardiovascular risk factors, and physical activity level, a strong dose-response relationship was evident between hours of TV viewing and fatal PE.
This association was most pronounced in the 40- to 59-year-olds. Using as a reference group subjects who watched less than 2.5 hours per day, those who watched 2.5-4.9 hours had an adjusted 3.14-fold increased risk of fatal PE. Individuals who watched 5 hours or more – less than the average length of two American football games – were at 6.49-fold increased risk.
The same dose-response association was evident in the full study population spanning ages 40 through 79 years at entry. However, the magnitude of risk attributable to prolonged television watching in the overall group wasn’t as great, since 60- to 79-year-olds face multiple age-related competing mortality risks. Still, 40- to 79-year-olds who watched at least 5 hours of TV daily had an adjusted 2.36-fold greater risk of fatal PE, compared with those who watched for less than 2.5 hours.
Mr. Shirakawa observed that the mechanism of injury is presumably the same as previously reported in studies of “shelter death” during the bombing of London during World War II, as well as “economy-class syndrome,” first described in conjunction with long-distance airplane flights in 1954. Basically, prolonged leg immobility leads to inadequate circulation and resultant venous clot formation. But prolonged TV watching is a much more common risk factor than is economy-class syndrome, he noted.
“The take-home message is this: Public awareness of the risk of pulmonary embolism from lengthy leg immobility is essential. To prevent the occurrence of pulmonary embolism, we recommend the same preventive behavior used against economy-class syndrome. That is, take a break, stand up, and walk around during the television viewing. And drink water to prevent dehydration; that is also important,” Mr. Shirakawa said.
Session cochair Dr. José Ramón González Juanatey observed that the true burden of PE triggered by prolonged TV watching is far greater than documented in the Japanese study because the analysis focused exclusively on fatal cases.
“Only about 10% of cases of pulmonary embolism are immediately fatal events,” commented Dr. González Juanatey of the University of Santiago de Compostela and president of the Spanish Society of Cardiology.
“The absolute risk may be fairly small, but it’s a devastating thing to have happen to you,” added cochair Dr. Ian Graham, professor of cardiovascular medicine at Trinity College, Dublin.
The Japan Collaborative Cohort Study has been funded by scientific grants from various Japanese health and education ministries. Mr. Shirakawa reported having no financial conflicts.