Study design: A nationwide cross-sectional study.
Objectives: To measure the associations between cigarette smoking (defined as serum cotinine concentration >15 ng/mL) and the 3-month prevalence of spinal pain (neck pain, low back pain, low back pain with pain below knee, and self-reported diagnosis of arthritis/rheumatism) and related limitations, and to verify whether these associations are mediated by serum concentrations of vitamin C.
Summary of background data: Cigarette smoking has been consistently associated with back pain, but this association has never been explained. Because vitamin C has recently been reported to be associated with spinal pain and related functional limitations, and the metabolism of vitamin C differs between smokers and nonsmokers, we hypothesized that the prevalence of spinal pain and related limitations might be greater among smokers because they are more susceptible to be in a state of hypovitaminosis C.
Methods: We conducted secondary analyses of National Health and Nutrition Examination Survey (NHANES) 2003 to 2004 data on 4438 individuals aged ≥20 years.
Results: Serum concentrations of vitamin C and cotinine were strongly and inversely correlated (r = -0.35, P < 0.0001). Smoking was statistically associated with the prevalence of neck pain [adjusted odds ratio: aOR: 1.25; 95% confidence interval (95% CI): 1.06-1.47], low back pain (aOR: 1.20; 95% CI: 1.04-1.39), and low back pain with pain below knee (aOR: 1.58; 95% CI: 1.13-2.22) and related limitations, with a dose-response relationship (P < 0.05). However, the associations between smoking and spinal pain were not mediated by concentrations of vitamin C.
Conclusion: These results confirm the relationship between smoking and spinal pain, but they do not support a mediating effect of vitamin C on this relationship.
Level of evidence: 2.