Age at menarche (when periods begin) is known to run in families. However, the balance of genetic and environmental influences on this has been unclear.
Scientists at The Institute of Cancer Research (ICR) analysed data from women participating in the Breakthrough Generations Study – a major UK-wide investigation into the causes of breast cancer – who had at least one other female relative also taking part.
They found that a woman’s age of menarche was significantly correlated with that of her relatives. For each 12 month delay in age at menarche of an older sister, mother or paternal aunt, there was a delay of around three months on average for the younger relative; and for a maternal grandmother or maternal aunt the delay in the younger relative was about 1.5 months. Age at menarche also strongly correlated between twins, particularly identical twins.
The researchers used mathematical modelling to find that genetic factors accounted for around 57 per cent of the variation in the age of menarche of women in the study. Environmental and behavioural factors from sharing an upbringing or family life did not appear to have any detectable effect; environmental factors not shared within families accounted for the other 43 per cent in variation.
The age at which menstruation begins is important because it has been linked to risk of a number of chronic diseases including breast cancer. Risk of breast cancer gradually increases with progressively younger age at menarche and older age at menopause, possibly because women are exposed to female sex hormones for a longer period of time. Each two year delay in menarche is associated with an estimated 10 per cent reduction in the relative risk of breast cancer.
“Our study findings suggest that genetic factors have a major influence on the age women in the UK begin menstruating, and these could have an impact on breast cancer risk,” lead author Danielle Morris of the ICR says. “Although some genes associated with age at menarche have been found, considerable genetic variation remains to be explained.”
The Breakthrough Generations Study is a comprehensive analysis of the causes of breast cancer. A partnership between Breakthrough Breast Cancer and the ICR, it began in 2003 and will follow more than 100,000 women participants for the next 40 years to unravel the lifestyle, environmental and genetic factors that cause the disease.
This arm of the study was funded by Breakthrough Breast Cancer, the ICR and the Sir John Fisher Foundation.
Media Contact: ICR Science Communications Manager Jane Bunce on 0207 153 5106 or after hours 077217 47900
Notes to editors:
The Breakthrough Generations Study is led by Professor Anthony Swerdlow, Head of the Section of Epidemiology at the ICR, and Professor Alan Ashworth, Chief Executive of the ICR and formerly head of the Breakthrough Breast Cancer Research Centre at the ICR.
Familial concordance for age at menarche: analysis from the Breakthrough Generations Study publishes today in the journal Paediatric and Perinatal Epidemiology
About 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)
- The ICR is Europe’s leading cancer research centre
- The ICR has been ranked the UK’s top academic research centre, based on the results of the Higher Education Funding Council’s Research Assessment Exercise
- The ICR works closely with partner The Royal Marsden NHS Foundation Trust to ensure patients immediately benefit from new research. Together the two organisations form the largest comprehensive cancer centre in Europe
- The ICR has charitable status and relies on voluntary income, spending 90 pence in every pound of total income directly on research
- As a college of the University of London, the ICR also provides postgraduate higher education of international distinction
- Over its 100-year history, the ICR’s achievements include identifying the potential link between smoking and lung cancer which was subsequently confirmed, discovering that DNA damage is the basic cause of cancer and isolating more cancer-related genes than any other organisation in the world
For more information visit www.icr.ac.uk
Breakthrough Breast Cancer
- Breakthrough Breast Cancer is a pioneering charity dedicated to the prevention, treatment and ultimate eradication of breast cancer. The charity fights on three fronts: research, campaigning and education.
- Breakthrough Breast Cancer funds ground-breaking research, campaign for better services and treatments and raise awareness of breast cancer. Through this work the charity believes passionately that breast cancer can be beaten and the fear of the disease removed for good.
Find more information at www.breakthrough.org.uk