Watching a favorite television show may feel relaxing, but in a
new study, the longer 30-somethings spent in front of the TV, the
stiffer their arteries - a sign of likely heart disease in the future."The fact that your arteries aren't elastic, it predisposes you to develop hypertension in later age and cardiovascular disease," Isabel Ferreira, senior epidemiologist at Maastricht University in the Netherlands, said.
Previous studies have linked TV watching to increased weight, cholesterol, blood pressure and diabetes, she and her colleagues write in the British Journal of Sports Medicine.
It's thought that people who spend more time in front of their TVs are less likely to get up and be physically active throughout the day, leading to a variety of problems associated with a sedentary lifestyle.
For the new study, researchers wanted to see whether early signs of damage caused by too little activity could be detected in younger adults.
They used data collected from 373 women and men, who filled out questionnaires about their TV viewing, exercise and other habits at age 32 and then again at age 36.
At age 36, each participant also had an ultrasound measurement of the stiffness of several major arteries in the body.
The researchers found those with the stiffest carotid artery, which is the main blood vessel in the head and neck, spent an average of about 20 more minutes per day watching TV, compared to people with the most elastic carotid artery.
Similar results were seen for stiffness of the femoral arteries in the legs.
Ferreira said the "critical cutoff" was about two hours per day of sitting. That's in line with current recommendations from the American Academy of Pediatrics for maximum screen time for children.
What's more, the negative effects of sitting did not appear to be offset by exercising.
"The funny thing is even if they do physical activity… that doesn't correct the bad effects of sedentary time," Ferreira said.Joel Stager, a professor at the Indiana University-Bloomington School of Public Health, said that those with stiff arteries wouldn't face immediate health problems. But it raises their risks later on.
"To be honest about this particular measure, it's more of an association of future problems," he said. "In other words, it's predictive of cardiovascular disease down the road."
Stager was not involved with the new study, but has researched arterial stiffening among college-age people.
"We are catching the early stages of this process," Ferreira said.
Stager also added that the new study cannot prove watching TV is what caused people's arteries to stiffen. It could be some other factor that goes along with TV watching, for instance, or young people with stiff arteries might be more likely to stay in and watch TV.
Ferreira said that more research into how watching TV may be tied to arterial stiffness is needed. But she said there is a take-home message for the average person.
"To put it simply, be active," she said. "And on top of that don't spend more than two hours sitting in front of your television, computer or laptop per day."
OFFICE workers who spend half of an eight-hour working day standing use 13 per cent more energy than colleagues who are seated, research shows.
Baker IDI Heart and Diabetes Institute Professor David Dunstan led the study, measuring the energy expenditure of 20 desk-based workers over two weeks while standing and sitting in a work environment.
During an average five-day working week, the extra energy used standing for four hours a day equated to a 45-minute brisk walk, Prof Dunstan said.
"This is a small increment but it's significant if you consider the difference over a working week," he said. "If people change their workplace environment and they were also meeting their regular exercise goals, it would have a positive effect on their health."
Prof Dunstan said much of the extra energy use came from the contraction of muscles used to keep the body upright.
He will reveal the preliminary findings of the study - which will later be used to analyse the effects on blood sugar and insulin levels while standing at work - at the Heart Foundation's National Conference, in Adelaide, tomorrow.
"It's really crept up on many Australians in the workplace - we're now sitting for about 80 per cent of our day at work," Prof Dunstan said.
Recent research found people who spend most of their days sitting - at work, on the bus or train and while watching TV - may not ward off heart disease, even if they exercise for 30 minutes a day as recommended.
"People shouldn't be disheartened by this," he said.
"We don't have an answer for how much exercise will offset time spent (sitting) but we need to consider what we are doing when we are not exercising."
Workers who don't have height-adjustable workstations should take a break, stand up and move every 20-30 minutes.
Heart Foundation national chief executive Dr Lyn Roberts said the study, funded by the foundation, showed no productivity was lost by standing.
"Heart Foundation recommends moving regularly throughout your day, from walking during your lunch break to standing up to answer your phone," she said.
