Bariatric Surgery Does Not Appear to Increase Fracture Risk

Joe Barber Jr, PhD

August 09, 2012

August 9, 2012 — The short-term risk for fracture does not appear to be increased by bariatric procedures, according to the findings of a population-based retrospective cohort study.

Arief Lalmohamed, PharmD, from Utrecht University in the Netherlands, and colleagues published their findings online August 7 in BMJ.

The authors mention that previous findings suggested a relationship between weight loss and changes in bone. "Restrictive procedures, such as vertical banded gastroplasty and laparoscopic adjustable banding, have been consistently reported to increase bone resorption, an increase that is similar in magnitude to that observed in other forms of weight reduction," the authors write. "The mechanisms behind the increase in bone resorption after weight loss are not fully understood, but two factors seem to be involved.

"Firstly, reduced fat volume may lead to a reduction in circulating concentrations of oestrogens, which are partly synthesised in adipose tissue. Secondly, a fall in leptin could result in an increase in osteoclast recruitment and bone turnover," they write.

The authors obtained data for patients who underwent bariatric surgery, as identified in the Clinical Practice Research Datalink between January 1987 and December 2010, and matched each patient by age, sex, body mass index (BMI), calendar time, and practice with as many as 6 individuals who had not undergone bariatric procedures. Among the 2079 surgery patients and 10,442 matched control patients, no significant differences were observed between the groups in risk for fracture (adjusted relative risk [ARR], 0.89; 95% confidence interval [CI], 0.60 - 1.33), including both nonosteoporotic (ARR, 0.90; 95% CI, 0.56 - 1.45) and osteoporotic (ARR, 0.67; 95% CI, 0.34 - 1.32) fractures.

The authors included bariatric surgery patients with a BMI of at least 30 kg/m2 and excluded those who underwent gastrointestinal surgery for cancer. The RR was adjusted for general risk factors such as age, sex, smoking status, and chronic disease history.

Compared with the matched control patients, patients who underwent surgery more commonly used anxiolytics, antidepressants, antidiabetics, and proton pump inhibitors in the preceding 6 months. A previous fracture (ARR, 2.44; 95% CI, 1.59 - 3.76), a history of cerebrovascular disease (ARR, 8.26; 95% CI, 4.40 - 15.52), and the use of anxiolytics in the previous 6 months (ARR, 1.82; 95% CI, 1.06 - 3.15) were associated with increased fracture risk. Compared with the subgroup with moderate reductions in excess BMI (1% - 50% loss), those with greater than 50% loss in excess BMI had an increased risk for fracture (ARR, 1.46; 95% CI, 0.55 - 3.85).

The limitations of the study included the lack of BMI data collection over short time intervals, a lack of information on events reported to secondary or intermediary services, the lack of data on bone mineral density, and the short follow-up time.

"Bariatric surgery does not have a significant effect on the risk of fracture," the authors conclude. "For the first few years after surgery, these results are reassuring for patients undergoing such operations, but do not exclude a more protracted adverse influence on skeletal health in the longer term."

Changes in Bone Physiology May Not Translate to Skeletal Fragility

Kurt A. Kennel, MD, from the Mayo Clinic in Rochester, Minnesota, noted the importance of this study. "These findings are important because they represent the first large-scale, albeit retrospective, assessment of fracture risk after bariatric surgery," Dr. Kennel told Medscape Medical News in an email. "Prior studies described mechanisms by which one would suspect an increased risk of fracture, but this study shows that these changes in bone physiology may not necessarily lead to a fragile skeleton."

However, Dr. Kennel mentioned that physicians should remain vigilant in monitoring all of the effects of bariatric surgery. "Bariatric procedures influence nutritional, mechanical, and hormonal parameters that can negatively affect bone health," Dr. Kennel told Medscape Medical News.

"Therefore, patients with known metabolic bone disease should proceed cautiously when considering bariatric surgery. In all patients, attention to correcting known deficits in nutrition (protein, calcium, vitamin D) and other known nutrition and lifestyle factors important for bone health remains important, even with this reassuring data."

This study was funded by a research grant from the International Osteoporosis Foundation and SERVIER. Dr. Lalmohamed and several coauthors are employed by the Division of Pharmacoepidemiology and Clinical Pharmacology at Utrecht Institute for Pharmaceutical Sciences, which has received unrestricted research funding from the Netherlands Organisation for Health Research and Development, the Dutch Health Care Insurance Board, the Royal Dutch Pharmacists Association, the private–publicly funded Top Institute Pharma, EU Innovative Medicines Initiative, EU 7th Framework Program, Dutch Medicines Evaluation Board, Dutch Ministry of Health, and industry (including GlaxoSmithKline and Pfizer). Dr. Kennel has disclosed no relevant financial relationships.

BMJ. Published online August 7, 2012. Full text

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