Women who fail to ovulate periodically lose large amounts of bone in their spine even though they may still be menstruating regularly, a new study has found. A yearlong test by doctors at the University of British Columbia in Vancouver also found that exercise had no effect on the rate of bone loss. It studied 66 women, aged 21 to 42.
The research, published in Thursday's New England Journal of Medicine, was designed to unravel the relationship between exercise, menstrual cycles and bone loss in younger women.
Previous studies have shown that women who exercise heavily may stop having periods. Among older women, the end of menstruation signals the beginning of bone deterioration.
All the women in the current study were menstruating, but not all ovulated. While the average overall bone loss for the group was 2 percent for the year, 13 women found not to be ovulating lost twice as much.
The team, led by Dr. Jerilynn Prior, was surprised to find that many women with normal menstrual cycles were not ovulating regularly.
"The women we studied appear to be representative of an urban, active population," the researchers said. "If the results of this study are confirmed, normal ovulation cannot be assumed to be present in menstrual cycles of normal length."
Women who take birth control pills, which prevent ovulation, were not an issue in the study because the pills contain hormones apparently lacking in the women in the study, said Dr. Deborah Reister of the New England Medical Center.
In another development Thursday, a University of Chicago researcher said that humans may soon expect an average lifetime of 85 years, but probably not much more, even if medical science defeats all of the major killer diseases.
That expectancy may be the upper limit because the human body by then is slowly deteriorating, researcher S. Jay Olshansky said Thursday.