To the Editor:

We thank Drs. Alexiou and Voulgaris for their interest in our article and their message regarding the role of elevated body mass index (BMI; i.e., obesity) in disc degeneration. We echo their sentiments and encourage them to publish their study results to increase awareness and understanding of BMI and its effects on spine health and patient outcomes.

Although we know that obesity is significantly associated with low back pain (1), numerous reports have also been published addressing its role in spine surgery outcomes. Consistent with the findings described by Alexiou and Voulgaris, obese patients, or those with elevated body mass indices, typically demonstrate an increased risk of intraoperative complications, worse clinical outcomes, higher frequency of spine surgeries, and increased hospital costs (2–4). In particular, studies have shown that being obese significantly increases the risk of recurrent disc herniation (5, 6); however, reports have also been published that contend otherwise (7, 8). This discrepancy may be attributed to ethnic variation, subject sampling and characteristics, statistical limitations, characterization of obesity, phenotype of global disc degeneration and spinal kinematics/alignment, and genetics, among other factors.

Although genetic factors have been noted to play a significant role in the development of disc degeneration, recent studies of twins have demonstrated that BMI continues to be an important determinant related to disc changes (9). Our Hong Kong Degenerative Disc Disease Cohort Study, an investigation of southern Chinese subjects, is one of the largest initiatives in the world to systematically assess imaging and clinical, genetic, and lifestyle/environmental factors related to disc degeneration. In time, it will provide further data about the role of BMI in disc degeneration severity and progression, pain and disability, as well as its interactive effects with genetic factors.

Obesity affects every population worldwide, and its prevalence continues to rise. With such trends, the degree of disc degeneration severity and associated low back pain and its consequences can be expected to further increase. Furthermore, spine surgery among obese patients may become more common, adding further importance to patient selection and personalized management options, as well as increasing the frequency of unsatisfactory outcomes. Therefore, we believe studies such as ours, as well as the upcoming work by Alexiou and Voulgaris, will bring much-needed attention to the effects of obesity on the spine in an effort to motivate future research to address the mechanisms involved in this process.

Dino Samartzis DSc*, Jaro Karppinen MD, PhD†, Danny Chan PhD‡, Keith D. K. Luk MCh(Orth), FRCSE, FRCSG, FRACS, FHKAM(Orth)‡, Kenneth M. C. Cheung MBBS, MD, FRCS, FHKCOS, FHKAM(Orth)‡, * University of Hong Kong, Pokfulam, Hong Kong, China, † University of Oulu, Oulu, Finland, ‡ University of Hong Kong, Pokfulam, Hong Kong, China.