Sydney, Feb 14 : The early onset of periods and early menopause can be linked to a heightened risk of Chronic Obstructive Pulmonary Disease (COPD) -- the umbrella term for progressive lung conditions that cause breathing difficulties -- according to a study.

Those who began menstruating before or at the age of 11 were 17 per cent more likely to develop COPD than those who did so at the age of 13; after the age of 16, the risk was 24 per cent higher, said the team from University of Queensland in Australia.

Menopause before the age of 40 was associated with a 69 per cent higher risk compared with those experiencing it naturally at the age of 50-51, while the risk was 21 per cent lower for those who went through it at or after the age of 54, said the team.

Further, the study published in the journal Thorax showed that women with children were at higher risk of COPD than childless women.

Compared with having two children, more than three was associated with a 34 per cent higher risk, while women with one child were at 18 per cent higher risk.

A history of miscarriage was associated with a 15 per cent higher risk of COPD, with the risk rising in tandem with the number of miscarriages: 28 per cent higher for two and 36 per cent higher for three or more.

Stillbirth (42 per cent), infertility (13 per cent) were also associated with a heightened risk of COPD, which includes emphysema and chronic bronchitis.

Women also seem to develop severe COPD at younger ages than men. And while smoking is a major risk factor, non-smokers with COPD are more likely to be women, the study noted.

'This is an observational study, so can't establish the cause,' said the researchers while acknowledging various limitations to their findings, including potentially influential factors like zero information on hormonal contraception and use of hormone replacement therapy.

The researchers believe that the female hormone oestrogen is likely to have a key role in COPD risk in women, because of its various effects on the lung. "The overall effect of oestrogen might differ depending on the timing," they suggest.

"In the early or middle reproductive stage, long or higher accumulated exposure to oestrogen would be detrimental to the lung, leading to a higher risk of COPD among women with early menarche or multiple live births.

"In the later stage, oestrogen may be protective, since earlier age at menopause or ovary removal (indicates shorter exposure to oestrogen) were associated with a higher risk of COPD."

Other factors, including autoimmune diseases, such as type 1 Diabetes, and social and environmental factors, such as air pollution, underweight, and socioeconomic deprivation, might also be influential, they added.

For the study, the team examined a collection of 27 observational studies, pooling individual-level data from more than 850,000 women in 12 countries. The women's health was monitored for an average of 11 years. During this time, 10,737 (4 per cent) women developed COPD at an average age of 63.

/IANS