Television sets have been given a lot of nicknames over the years: The tube. The telly. The idiot box. Now, it might be time for one more nickname — the widowmaker.

Using data from more than 500,000 people in the United Kingdom, scientists in England and Hong Kong have concluded that people who watched four or more hours of television a day have the greatest risk of heart disease.

Before they could make that conclusion, the scientists had a pressing question to answer: How much is the risk of heart disease related to genetic factors versus the sedentary, TV-watching lifestyle?

First, the scientists created a scoring system to determine the risk of developing heart disease based on 300 genetic variants. Then, they focused on television habits.

As TV time decreased, so did the risk of heart disease. People who watched the most television every day faced the biggest disease risk. Two to three hours of daily TV viewing cut that risk by 6%. Those who tuned in for less than an hour a day were 16% less likely to get heart disease.

Those findings held true regardless of genetic risk factors. In other words, good genes might not help overcome the harmful effects of too much TV.

Interestingly, the researchers found no similar association between leisure-time computer use and the risk of heart disease. They have a few theories as to why that’s so: TV viewing typically happens after dinner, which is often the day’s most calorie-heavy meal. That’s sedentary time just as fat, sugar and cholesterol levels are peaking. Most people also tend to snack more in front of the TV than a computer.

But for TV addicts, the news isn’t all bad: An ounce of prevention is as close as the off switch.