Recent research has turned up two new clues of an increased stroke risk—but discounted a third suspected though unconfirmed hint. The newly discovered factors are the habit of unintentionally falling asleep during the day, and mammograms that reveal benign arterial calcifications. Depression, however, appears to be of little or no significance.

The findings on daytime sleepiness were presented at the American Stroke Association’s international conference in New Orleans in February. Researchers evaluated 2,153 subjects 40 years of age and older (mean age: 73). Over an average follow-up of 2.3 years, those who dozed significantly during the day proved to be 4.5 times more likely to suffer a stroke than people who didn’t nap.

Individuals who did a moderate amount of daytime sleeping had a risk of stroke 2.6 times higher than the no-doze group. At the same conference, investigators from the University of Missouri Medical School in Columbia reported that 115 of 204 women who had suffered a stroke (56%) had mammograms exhibiting benign arterial calcifications in the blood vessels. Only 10% of women in the general population have mammograms reflecting such findings.

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The findings on depression come from a study conducted at the University of Cambridge in England, where researchers followed 20,627 men and women for 8.5 years (Neurology. 2008;70:788-794). They found that the odds of having a stroke were the same for those who experienced a major episode of depression as for those who did not. Previous studies have shown that stroke often leads to depression, but the evidence was mixed as to whether the reverse was true.