Sleep quality and chronic neck pain: a co-twin study

STUDY OBJECTIVES: Sleep quality and chronic neck pain (NP) are associated. However, the genetic influences on this association have not been explored. This study investigated the genetic and environmental influences on the association between sleep quality and chronic NP. METHODS: The sample comprised 2,328 individual twins from the Murcia Twin Registry (Spain). A bidirectional cotwin logistic regression analysis was performed (sleep quality assessed as the exposure and chronic NP as the outcome and vice versa). Analysis included 2 sequential stages: total sample analysis and within-pair twin case-control analysis. RESULTS: Sleep quality was significantly associated with chronic NP in the total sample analysis (adjusted odds ratio [OR]: 1.09; 95% confidence interval [CI]: 1.06, 1.12; P < .001); in the cotwin case-control analysis, including both monozygotic and dizygotic twin pairs (adjusted OR: 1.10; 95% CI: 1.04, 1.17; P = .001); in dizygotic pairs (Adjusted OR: 1.11; 95% CI: 1.03, 1.19; P = .005); but not in monozygotic pairs (adjusted OR: 1.08; 95% CI: 0.98, 1.19; P = .118). Chronic NP was significantly associated with poor sleep quality in the total sample analysis (adjusted OR: 1.80; 95% CI: 1.43, 2.26; P < .001); in the cotwin case-control analysis, including both monozygotic and dizygotic twin pairs (Adjusted OR: 1.63; 95% CI: 1.07, 2.47; P = .023); in dizygotic pairs (Adjusted OR: 1.80; 95% CI: 1.05, 3.09; P = .031), but not in monozygotic pairs (adjusted OR: 1.67; 95% CI: 0.80, 3.48; P = .170). CONCLUSIONS: The association between sleep quality and chronic NP is partially confounded by genetic factors.