Body Mass Index and Smoking Predict Lumbar Disk Degeneration among Young Finnish Males

Abstract

Introduction The role of environmental factors in lumbar intervertebral disk degeneration (DD) in young adults is largely unknown. Therefore, we investigated whether body mass index (BMI), smoking, and physical activity are associated with lumbar DD among young adults. Materials and Methods The study population, Oulu Back Study (OBS), belongs to the 1986 Northern Finland Birth Cohort (NFBC 1986), consisting originally of 9479 children. Of 2969 eligible cohort members, 1987 subjects answered to a survey at the mean age of 18. Of these, 874 participated in physical examination at the mean age of 19 and were invited to lumbar MRI study. A total of 558 young adults (325 females and 233 males) underwent MRI that used a 1.5-T scanner at the mean age of 21. Each lumbar intervertebral disk was graded as normal (0), mildly (1), moderately (2), or severely (3) degenerated. We calculated a sum score of the lumbar DD, and analyzed the associations between environmental risk factors and DD using ordinal logistic regression. In the univariate models, the determinants included pack-years of smoking at 19 years, mean level of physical activity in metabolic equivalent hours per week at 16 and 19 years, body mass index (BMI), weight, height and waist circumference (WC) at 16 and 19 years. Because of collinearity, only one weight-related factor was included in the multivariate model. All analyses were stratified by gender. Results Of the 558 subjects, 257 (46%) had no DD, 117 (21%) had sum score of one, 93 (17%) sum score of two, 43 (8%) sum score of three, and 49 (8%) sum score of four or higher. In the univariate analyses, BMI, height, weight, and WC at 16 and 19 years were associated with DD among males. Among females, height at 16 and 19 years was associated with DD. Smoking of at least four pack-years was associated with DD among males. In the multivariate model, BMI at 16 years was associated with DD sum score among males (OR 2.35; 95% CI, 1.19–4.65) but not among females (OR 1.29; 95% CI, 0.72–2.32). Smoking of at least four pack-years tended to be associated with DD among males, but not among females (OR 2.41; 95% CI, 0.99–5.86 and 1.59; 95% CI, 0.67–3.76, respectively). Level of physical activity was not associated with DD. Conclusion BMI at 16 years and 19 years predicted lumbar DD at 21 years among young males whereas no associations were found among females. Smoking of at least four pack-years tended to be associated with DD among males. These results suggest that environmental factors are associated with DD among young males. I confirm having declared any potential conflict of interest for all authors listed on this abstract No Disclosure of Interest None declared