Lifestyle and health factors starting from before birth may affect the age at which a girl begins her periods, a major new study published today in the British Journal of Cancer shows.
Scientists at The Institute of Cancer Research (ICR) found that mothers who smoke or suffer pre-eclampsia during pregnancy were more likely to have daughters who menstruated early. Other factors linked to early menstruation included having a low birth weight, being a singleton (not a twin), not being breastfed, having fewer siblings, having an early birth order (being an older sibling) and being non-white.
The study also confirmed that girls who were heavier or taller than other children at age seven and exercised little as children were more likely to start their first period at a young age.
Age at menarche (when periods begin) has long been established as a risk factor for breast cancer, possibly because these women are exposed to female sex hormones for a longer period of time. Disease risk gradually increases with progressively younger age at menarche and older age at menopause.
Analysis leader Danielle Morris, from the ICR, said: “This research shows that there are factors influencing age at first period that likely begin even before a child is born, yet might affect risk of developing breast cancer decades later.
“A girl who takes more exercise is likely to start her periods later in life. We know exercising regularly as an adult can help reduce the risk of developing breast cancer. This study shows that exercising as a child could also potentially have an effect on breast cancer risk later in life.”
The study found average age of menarche was 12.7 years, with five per cent of participants starting before the age of 11 and 10 per cent at age 15 or older. When the scientists examined several factors in combination they found that, for example, a non-white girl who was heavier and taller than her peers at age seven could begin menstruating nearly two years earlier on average than a white girl of average height and weight.
Both genetics and environment were known to affect the age at which menstruation starts but until now few specific factors have been identified, most likely because published studies have been too small to reveal trends.
This large-scale investigation analysed data from 81,000 UK women taking part in the Breakthrough Generations Study, a comprehensive analysis of the causes of breast cancer. The study, a partnership between Breakthrough Breast Cancer and the ICR, will follow the 100,000 women participants for the next 40 years to unravel the lifestyle, environmental and genetic factors that cause the disease.
The Breakthrough Generations Study – led by Professor Anthony Swerdlow, Head of the Section of Epidemiology at the ICR, and Professor Alan Ashworth, Director of the Breakthrough Breast Cancer Research Centre at the ICR - costs around £1 million each year to support, which pays for ongoing collection, storage and analysis. The study is supported by a range of funders, including M&S and Walk The Walk. The researchers on this paper were supported by the Sir John Fisher Foundation, the ICR and Breakthrough Breast Cancer.
Breast cancer is the most commonly diagnosed cancer in the UK – nearly 46,000 women and around 300 men are diagnosed every year
Breast cancer accounts for nearly one in three of all female cancers
More than 1,000 women die of breast cancer every month in the UK
The good news is that more women than ever in the UK are surviving breast cancer thanks to better awareness, better treatments and better screening.
The Institute of Cancer Research (ICR)
