Girls’ first period linked to genes, not diet: Study

Scientists claim that genetic factors have a major influence on the age women begin menstruating, and these could have an impact on breast cancer risk.

In recent decades it has been thought the average age of menarche - when periods begin - had been falling as girls were better fed, grew faster and their bodies matured earlier.

But scientists at the Institute of Cancer Research, a college of the University of London, found a woman’s age of menarche was significantly linked with that of her relatives, including her mother, older sister, grandmother or aunts, reports the Daily Mail.

They used mathematical modelling to find that genetic factors accounted for around 57% of the variation in the age of menarche of women in the study.
 
The remainder was accounted for by environmental factors not shared within families.

The age at which menstruation begins is important because it has been linked to a risk of number of chronic diseases including breast cancer.

Risk of breast cancer gradually increases with a progressively younger age at first period, and older age at menopause, possibly because women are exposed to female sex hormones for a longer period of time.

The study looked at almost 26,000 related women, all of whom had at least one relation involved, taking part in a major UK-wide investigation into the causes of breast cancer.

For each 12 month ‘delay’ in age at first period of a mother or older sister compared with the average, the younger relative had a delay of around three months.

This means if one girl’s mother started her periods at 12, and another at 13, there would be a trend for the daughter of the woman starting later to start three months closer to her mother’s age of menarche.

The report is published in the journal Paediatric and Perinatal Epidemiology.