Researchers followed more than 200,000 men and women for up to 38 years and found that regularly consuming sweetened drinks, either containing sugars or artificially sweetened, was associated with a rise of about 13 percent in the risk of developing high blood pressure.

Carbonated and cola drinks were most strongly linked to a risk for hypertension, but fruit sugar, or fructose, in drinks did not stand out as a driving factor, the group reported in the Journal of General Internal Medicine.

"We don't know what causes the increased risk in artificial- or sugar-sweetened beverages," said Lisa Cohen, lead author of the study and a researcher at the University of Maryland Medical Centre.

"It's hard to say that from the fructose itself you're increasing your hypertension risk."

New York City Mayor Michael Bloomberg last week proposed a ban on large-size sugary sodas, the latest in a string of public health initiatives that include a campaign to cut salt in restaurant meals and packaged foods.

Earlier studies had implicated fructose as a factor related to a risk of high blood pressure, but Cohen noted that those have only taken a snapshot in time and could not determine which came first, the high blood pressure or taste for sweet drinks.

Cohen and her colleagues looked at data from three massive studies, including nearly 224,000 healthcare workers, whose diet and health were tracked for 16 to 38 years. No participants had diagnosed high blood pressure at the start of the study.

Over time, those who drank at least one sugar-sweetened beverage a day had a 13 percent increased risk of developing hypertension relative to those who only had a sweet drink once a month or less.

Similarly, people who drank at least one artificially-sweetened drink a day had a 14 percent increased risk of developing hypertension relative to those who had few or none.

To see if it was the fructose that was responsible, researchers also looked at people who had high levels of fructose in their diets from other sources, such as fruits.

Among people who consumed 15 percent of their calories from fructose sources other than drinks, the risk of developing hypertension was either lower or the same as people who ate very little fructose.

"You would think if fructose were the causative factor, then eating a lot of apples (for example) would also increase your risk of hypertension," Cohen told Reuters Health.

The "markedly" stronger link between carbonated sweet drinks and increased hypertension risk might be explained by the larger serving sizes associated with sodas, or some other unknown ingredient common to all of them, the researchers said - but further research is needed.