Table 2

Associations between age at menarche and prevalence of chronic LBP in HUNT2 in cross-sectional analysis

Total number of women in category of age at menarche*Number of women with chronic LBPCrude AR of chronic LBP (%)RR (95% CI) with adjustment for age onlyRR (95 % CI) with additional adjustment†
Number of women included27 69727 69724 951
Age at menarche (year)
≤11248780632.41.39 (1.30 to 1.49)1.33 (1.24 to 1.43)
125536149927.11.17 (1.11 to 1.24)1.13 (1.06 to 1.21)
137789195325.11.08 (1.02 to 1.14)1.07 (1.01 to 1.14)
146861171325.01.00 (reference)1.00 (reference)
15375999426.41.03 (0.96 to 1.10)1.04 (0.97 to 1.12)
1697525225.80.99 (0.89 to 1.11)1.02 (0.91 to 1.15)
≥172908328.61.12 (0.93 to 1.35)1.31 (1.08 to 1.59)
P for categorical effect<0.001<0.001
P for linear trend<0.001<0.001
P for quadratic effect‡<0.001<0.001
  • *In analysis adjusted for age only.

  • †Adjustment for age, BMI, physical activity, education, smoking, nulliparity and age at first delivery.

  • ‡In model also including linear effect.

  • AR, absolute risk; BMI, body mass index; HUNT, Trøndelag Health Study; LBP, low back pain; RR, relative risk.