Menopausal hormone therapy, oral contraceptives and risk of chronic low back pain: the HUNT Study

Table 4 Associations in HUNT2 between use of OC and prevalence of chronic LBP in cross-sectional analysis, among women aged 20–69 years

	Total number of women^a	Number of women with chronic LBP (%)^a	PR (95% CI) with adjustment for age only	PR (95% CI) with comprehensive adjustment^b
Use of OC
Number of women included			23,593	19,637
Never	10,441	2971 (28.5)	1.00 (reference)	1.00 (reference)
Former	10,771	2776 (25.8)	1.16 (1.11–1.23)	1.17 (1.10–1.23)
Current	2381	338 (14.2)	0.96 (0.86–1.08)	1.01 (0.89–1.15)
P for categorical effect			< 0.001	< 0.001
Duration of use of OC (year)
Number of women included			23,060	19,222
0	10,441	2971 (28.5)	1.00 (reference)	1.00 (reference)
0-4^c	6402	1576 (24.6)	1.18 (1.11–1.25)	1.16 (1.09–1.24)
5–9	3786	768 (20.3)	1.08 (1.00–1.17)	1.11 (1.03–1.21)
10–14	1728	401 (23.2)	1.09 (0.99–1.20)	1.09 (0.98–1.20)
≥ 15	703	200 (28.4)	1.16 (1.03–1.31)	1.18 (1.04–1.34)
P for categorical effect			< 0.001	< 0.001
P for linear trend^d			0.09	0.35

HUNT Trøndelag Health Study, OC Oral contraceptives, LBP Low back pain, PR Prevalence ratio, CI Confidence interval, MHT Menopausal hormone therapy
^aIn analysis adjusted for age only
^bAdjustment for age, BMI, physical activity, education, smoking, age at menarche, nulliparity, age at first childbirth, use of systemic MHT
^cMust have used OC for at least one month
^dAmong all women who had used OC for at least one month

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