Sleep as a prognostic factor in low back pain: a systematic review of prospective cohort studies and secondary analyses of randomized controlled trials

Sleep problems are common in individuals with low back pain (LBP) and sleep restriction seems to be associated with impaired pain processing. Our objective was to investigate whether sleep is associated with future LBP outcomes (i.e., pain intensity, disability, and recovery) in adults. We conducted a systematic review of prospective cohort studies and secondary analyses of randomized controlled trials (registration - PROSPERO CRD42022370781). In December 2022, we searched the MEDLINE, Embase, CINAHL, and PsycINFO databases. Fourteen studies, totaling 19,170 participants were included. Thirteen studies were rated as having high risk of bias (QUIPS tool). We used vote-counting and meta-analysis approaches to synthesize the data. We found associations between baseline sleep with future pain intensity, recovery, and between changes in sleep with changes in pain intensity, changes in disability, and recovery. We further synthesized outcomes as 'overall LBP improvement' outcome. Baseline poor sleep was moderately associated with non-improvement in LBP in the long-very long term (OR 1.55, 95% CI 1.39 to 1.73; three studies providing unadjusted effect sizes), and non-improvement in sleep was largely associated with non-improvement in LBP in the short-moderate term (OR 3.45, 95% CI 2.54 to 4.69; four studies providing unadjusted effect sizes). We found no association between baseline sleep with future disability and overall LBP improvement in the short-moderate term. Therefore, sleep may be a prognostic factor for pain intensity and recovery from LBP. All findings were supported by low to very low-quality evidence. Better-conducted studies are needed to strengthen our certainty about the evidence.