The Study: Body mass index is associated with lumbar disc degeneration in young Finnish males: subsample of Northern Finland birth cohort study 1986

The Facts:
a. The authors sought to determine if BMI (body mass index), smoking and activity level are associated to disc degeneration.
b. They studied 558 young adults.
c. At the mean age of 21 they each had an MRI of the lumbar spine.
d. The authors determined that physical activity was not associated with disc degeneration in this group in either males or females.
e. High BMI at age 16 and high pack-years of smoking were both associated with disc degeneration in the males in this group but not in females.
f. The authors speculated that the high BMI might affect the discs by creating a “systemic inflammatory state”.

Take Home:
Being overweight and smoking appear to affect the discs of young males.

Reviewer’s Comments:
Two scientists whose work I enjoy reading recently said that if there is one article that says something that goes against what a number of other articles have said in the past you should be skeptical. Well in that vein, it seems to me that increased physical activity of the type where you receive trauma to the spine (think football, rugby, falls during gymnastics or cheerleading) should tend to adversely affect the disc. But perhaps the years my tuition was paid in return for my playing rugby at Palmer has nothing to do with the speed with which I rise from bed in the last few years.

Reviewer: Roger Coleman DC

Editor’s Comments: Just a bit of personal speculation on why spinal health in the females may not have been impacted by higher BMI. Since BMI is calculated as weight divided by height, it would seem plausible that even though females in the study may have presented with elevated body fat levels their actual body weight is likely to have been significantly lower on average than that of the males. It may be possible that the mean weight of females in the study simply didn’t rise to the threshold necessary to induce spinal degeneration.

Editor: Mark R Payne DC

Reference: Takatalo J, Karppin J, Taimels S, Niinimaki J, Laitinen J, Blanco Sequeiros R, Pannanen M, Remes J, Nayha S, Tammelin T, Korpelainen R, Tervonen O. Body mass index is associated with lumbar disc degeneration in young Finnish males: subsample of Northern Finland birth cohort study 1986. BMC Musculoskelet Disord 2013;14:87. doi: 10.1186/1471-2474-14-87.

Body mass index is associated with lumbar disc degeneration in young Finnish males
Subsample of Northern Finland birth cohort study 1986
Takatalo J

BMC Musculoskelet Disord. 2013 Mar 11;14:87. doi: 10.1186/1471-2474-14-87

Abstract
BACKGROUND:
The role of environmental factors in lumbar intervertebral disc 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.

METHODS:
The Oulu Back Study (OBS) is a subpopulation of the 1986 Northern Finland Birth Cohort (NFBC 1986) and it originally included 2,969 children. The OBS subjects received a postal questionnaire, and those who responded (N = 1,987) were invited to the physical examination. The participants (N = 874) 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 disc 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 (smoking, physical activity and weight-related factors assessed at 16 and 19 years) and DD using ordinal logistic regression, the results being expressed as cumulative odds ratios (COR). All analyses were stratified by gender.

RESULTS:
Of the 558 subjects, 256 (46%) had no DD, 117 (21%) had sum score of one, 93 (17%) sum score of two, and 92 (17%) sum score of three or higher. In the multivariate ordinal logistic regression model, BMI at 16 years (highest vs. lowest quartile) was associated with DD sum score among males (COR 2.35; 95% CI 1.19-4.65) but not among females (COR 1.29; 95% CI 0.72-2.32). Smoking of at least four pack-years was associated with DD among males, but not among females (COR 2.41; 95% CI 0.99-5.86 and 1.59; 95% 0.67-3.76, respectively). Self-reported physical activity was not associated with DD.

CONCLUSIONS:
High BMI at 16 years was associated with lumbar DD at 21 years among young males but not among females. High pack-years of smoking showed a comparable association in males, while physical activity had no association with DD in either gender. These results suggest that environmental factors are associated with DD among young males.

PubMed Reference:  http://www.ncbi.nlm.nih.gov/pubmed/23497297