Japanese women are generally not at high risk for heart attacks — unless they live with in-laws, according to a new study.

Married Japanese women who live with both their husbands and a set of parents — in Japan, that almost always means the husband’s parents, according to the researchers — were three times more likely to suffer a heart attack than those living just with their husbands.

Having children at home also was associated with an increased risk of heart attacks among Japanese women, but not by as much, the study found. When women lived with both parents and children, the risk of heart attacks doubled rather than tripled.

The heart attack risk was slightly higher among women living with both spouses and children, the study found.