. Author manuscript; available in PMC: 2020 Sep 1.

Published in final edited form as: Spine (Phila Pa 1976). 2019 Sep 1;44(17):1220–1227. doi: 10.1097/BRS.0000000000003053

Table 3.

Baseline PTSD symptoms and risk of incident chronic back pain over 5-Year follow-up^*

		Bivariable associations^a		Multivariable-adjusted associations^ab

	n of total complete pairs	RR (95% CI)	p value	RR (95% CI)	p value
Primary outcome

Any chronic back pain^c	83	1.6 (1.2–2.1)	0.001	1.5 (1.2–2.0)	0.002

Secondary outcomes

Chronic low back pain	91	1.6 (1.2–2.1)	0.001	1.6 (1.2–2.1)	0.001
Chronic mid/upper back pain	83	3.7 (1.6–8.2)	0.002	2.7 (1.1–6.3)	0.02

n=sample size, RR= risk ratio of incident chronic back pain with baseline PTSD symptoms*

PTSD (post-traumatic stress disorder) symptoms defined as PCL≥30 at baseline. Chronic back pain is defined as back pain of duration ≥ 3 months.

Within-pair analyses of associations of PTSD symptoms with each back pain outcome, from generalized linear models in which twins are compared to their co-twins.

Adjustment for having received or applied for Veterans Affairs (VA) service connection

Back pain in either of the low back [lumbar] or mid/upper back [thoracic] regions