Girls who start their periods before the age of 12 'at greater risk of stroke in later life'
Girls who enter puberty before the age of 12 are much more likely to suffer from heart disease or a have a stroke in later life, warns new research.
The study also showed that girls who start their periods early are also more likely to enter the menopause early, as well as suffer pregnancy complications, and have a hysterectomy.
Previous research has suggested that certain reproductive risk factors may be linked to an increased risk of heart disease or stroke, but the findings have been mixed.
The Oxford University team behind the new study drew on data from the UK Biobank, a study of more than half a million men and women up to the age of 69, recruited between 2006 and 2010.
Participants filled in questionnaires on their lifestyle, environment, and medical history, which included a wide range of reproductive factors.
They also took tests to assess their physical and functional health, and provided urine, blood, and saliva samples.
In all, the health of 267,440 women and 215,088 men - none of whom had cardiovascular disease when they entered the study - was tracked up to March 2016 or until they had their first heart attack or stroke, whichever came first.
The average age of the women at the start of the study was 56, and just over half (51 per cent) came from the most affluent third of the UK population. Six out of 10 had never smoked.
The average age at which they had started having periods was 13; most (85 per cent) had been pregnant, and nearly half (44 per cent) had had two kids. On average, they were 26 when they had their first child.
One in four of the women had miscarried, and three per cent had suffered a stillbirth. Nearly two-thirds had gone through the menopause, at an average age of 50.
Just over four out of 10 of the men (42 per cent) had fathered two children before the start of the study.
During a monitoring period spanning around seven years, 9,054 cases of cardiovascular disease were recorded, a third of which were in women (34 per cent).
This included 5,782 cases of coronary artery disease (28 per cent women) and 3,489 cases of stroke (43 per cent women).
Analysis showed that after taking account of potentially influential factors, women who had started having periods before the age of 12 were at 10 per cent greater risk of cardiovascular disease than those who had been 13 or older when they started.
Similarly, those who went through the menopause early - before the age of 47 - had a 33 per cent heightened risk of cardiovascular disease, rising to 42 per cent for their risk of stroke, after taking account of other potentially influential factors.
Previous miscarriages were associated with a higher risk of heart disease, with each miscarriage increasing the risk by six per cent.
And stillbirth was associated with a higher risk of cardiovascular disease in general (22 per cent) and of stroke in particular (44 per cent).
Hysterectomy was also linked to a higher risk of cardiovascular disease (12 per cent) and of heart disease (20 per cent).
And those who had had their ovaries removed before a hysterectomy were twice as likely to develop cardiovascular disease as those who hadn't undergone the procedures.
The researchers said that young age at first parenthood seemed to be another risk factor, with each additional year of age lessening the risk of cardiovascular disease by around three per cent.
But the association between the number of children and cardiovascular disease was similar for men and women, suggesting that social, psychological, and behavioural factors may be more important than biological ones.
The researchers said it was an observational study, so no firm conclusions can be drawn about cause and effect, added to which the information on reproductive factors was based on memory, so may not have been completely accurate.
But the study was large, and the researchers were able to account for a range of potentially influential factors.
Study author Dr Sanne Peters, of The George Institute for Global Health at Oxford University, said: "More frequent cardiovascular screening would seem to be sensible among women who are early in their reproductive cycle, or who have a history of adverse reproductive events or a hysterectomy, as this might help to delay or prevent their onset of cardiovascular disease."