More than 8500 women from five northern European countries were surveyed about their respiratory health and hormonal patterns between 1999 and 2001.
Women who were menopausal, pregnant, or taking oral contraceptives/hormone replacement therapy were excluded from the final analysis, leaving just over 6,000 women in total. The entire sample had originally been surveyed about their respiratory health as part of a large European study, which ran from 1990 to 1994 (ECRHS I).
Around one in four women (23%) had irregular periods. This translated into around one in seven women (15%) aged between 25 and 42, and over a third (37%) of those aged between 43 and 54.
Among the younger women, those who weighed the most, or were the shortest or tallest, tended to have irregular periods. Among the older women, irregular periods were associated with smoking and with the timing of the menopause. And after taking account of other influential factors, rates of asthma and allergy were significantly higher in younger women who had irregular periods than in those with regular periods.
The potential impact of asthma medication on the menstrual cycle was not evident, as the trend was also seen among women whose symptoms were not being treated. This pattern was seen across all the centres.
The authors suggest that common factors may underlie both irregular periods and asthma/allergy, including fetal development and insulin resistance. Previous research has also found an association between poorer lung function and insulin resistance.
MEDICA.de; Source: British Medical Journal