People are in more danger of suffering strokes on Mondays -- especially those in their 40s and 50s who are in their prime, probably because of the stress of returning to work as well as fatigue from weekend leisure activities, according to a recent study by a group of researchers.

"People who enter their 40s should go to bed early on Sunday and start work slowly on Monday because they are more likely to develop strokes," said Keiko Kurashiki, a professor at Tottori University's faculty of medicine, who led the group.

The research, conducted by utilizing data compiled by Tottori Prefecture through health centers and hospitals, covered about 12,000 patients who had suffered strokes over a 17-year period in the prefecture.

The group analyzed the data by dividing patients who suffered strokes for the first time between 1985 and 2001 into two groups -- 2,116 patients aged between 40 and 59 and 10,413 patients aged 60 or above who had retired.

The research showed that 12.6 percent of men in the 40-59 age bracket suffered strokes on Sundays, compared with 11.4 percent of women in the same age group.

But on Mondays that figure jumped 1.3-fold to 16.9 percent for men and 1.5-fold to 17.2 percent for women.

Those aged 60 or above also faced the highest risk on Mondays, with 15.2 percent of men and 16.3 percent of women suffering strokes.

But the percentage differences with weekends were not as big as those for the 40-59 age group -- indicating the risk of strokes depends on whether one works.

Meanwhile, people aged 60 or above also saw a high risk of developing strokes on Thursdays, apparently because they start to get tired in the middle of the week, the research showed.