Vitamin C is not the Missing Link Between Cigarette Smoking and Spinal Pain

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.