Does the risk of chronic low back pain depend on age at menarche or menopause? A population-based cross-sectional and cohort study: the Trøndelag Health Study.

Objective: In most population-based studies of low back pain (LBP), women have a higher risk than men, possibly reflecting hormonal influences. The aim of this study was to explore associations between age at menarche and menopause and risk of chronic LBP.

Design: Population-based cross-sectional and cohort study designs.

Setting: The HUNT2 and HUNT3 medical surveys of the entire population of Nord-Trøndelag County in Norway.

Main Outcome Measure: Prevalence or risk of chronic LBP, defined as LBP persisting at least 3 months continuously during last year.

Participants: Associations between age at menarche and prevalence of chronic LBP were examined in cross-sectional data from HUNT2, comprising 27 697 women aged 20-69 years, with 7300 women reporting LBP. The corresponding cohort data included 11 659 women without LBP at baseline in HUNT2, with 2353 women reporting LBP at follow-up 11 years later in HUNT3. Cross-sectional data on age at menopause or premenopausal status included 11 332 women aged 40-69 years, with 3439 women reporting chronic LBP. Corresponding cohort data included 7893 women without LBP at baseline, of whom 1100 developed LBP.

Methods: Associations between age at menarche or menopause and risk of chronic LBP were examined by generalised linear modelling.

Results: A U-shaped association was indicated between age at menarche and risk of chronic LBP, both in the cross-sectional and cohort studies. Age at menarche ≤11 years was associated with an increased risk of chronic LBP, with a relative risk of 1.32 (95% CI 1.15 to 1.52), compared with age 14 years at menarche, after relevant adjustments. Corresponding cross-sectional crude absolute risks were 32% and 25%, respectively. No association was established between age at menopause and risk of LBP. Being premenopausal had no influence on risk.

Conclusions: In contrast to results for age at menopause, the association with age at menarche suggests that hormonal factors affect the risk of LBP.