A constant drone of low-level traffic noise may slightly raise your risk of cardiovascular disease, according to British researchers.

The study included data from the nearly 450,000 people admitted to London hospitals with cardiovascular disease over an eight-year period. Researchers estimated how much traffic noise these people were exposed to, day and night.

Compared with an average noise level below 55 decibels, levels above 60 decibels were linked to higher rates of being hospitalized for a stroke—about 9% higher among those 75 and older and 5% higher in people ages 25 to 74. Deaths from all causes were 4% higher for people in noisier neighborhoods. The results were adjusted for socioeconomic factors, smoking, air pollution, and other measured confounding factors.

Sixty decibels is comparable to the sound in a crowded restaurant, so not especially loud. But the cumulative effect over years could raise stress hormones, which can contribute to cardiovascular risk, the authors say. The study was published online June 23, 2015, by the

European Heart Journal

.