A new study has found that women who got their first menstrual period (menarche) at a younger age are more likely to report chronic pain in adulthood.

The findings of the study were published in the journal PAIN, the official publication of the International Association for the Study of Pain (IASP). "We found strong associations between age at menarche and chronic pain outcomes in adult women," according to the new research by Charlotte Indre Lund, PhD fellow in Epidemiology at Oslo University Hospital, and colleagues.

The findings add to previous evidence suggesting that increased estrogen levels associated with early menarche may contribute to pain, and to sex differences in pain in general. The study included data on more than 12,000 women (average age 55) participating in the Tromso Study, an ongoing population study of the health of people in northern Norway.

The researchers analysed associations between women's self-reported age at menarche and the presence and characteristics of chronic pain. The women's reported average age at menarche was about 13 years. About 40 per cent of women reported experiencing chronic pain. Women with younger age at menarche were more likely to have chronic pain.

After adjustment for potential confounding factors, the relative risk of chronic pain decreased by 2 per cent for each one-year delay in menarche. Absolute risk decreased by 1.1 to 1.4 percentage points per year. Across the full range of reported ages - from 9 to 18 years - the absolute risk of chronic pain differed by 12.6 percentage points.

Older age at menarche was associated with lower rates of chronic pain in each of the 10 body regions assessed, with the strongest associations for chest and abdominal pain. Younger age at menarche was associated with a longer duration of pain. Based on recently updated criteria, the prevalence of chronic widespread pain (CWP) was 7.4 per cent. Later menarche was associated with a decreased risk of experiencing CWP, with a risk ratio of 7 per cent and an absolute risk difference of 1.5 percentage points per year.

Based on the new findings, the researchers conclude that "Age at menarche is an independent risk factor for chronic pain, site-specific chronic pain, and chronic widespread pain and (thereby) contribute to the explanation of sex differences in pain." Each additional year of delay to the first menstrual period is associated with a reduced risk for having chronic pain lasting 5 years or longer, as well as a reduced risk of CWP.