Bone strength persists 1 year after sleeve gastrectomy for teens, young adults with obesity
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Adolescents and young adults with obesity who underwent sleeve gastrectomy experienced a reduction in bone mineral density measures in the year after surgery when compared with nonsurgical controls, but did not experience a decrease in bone strength despite significant weight loss, according to findings published in Bone.
“The adolescent and young adult years are a critical time for bone accrual toward attainment of peak bone mass (in the third decade of life), which is a key determinant of bone health and fracture risk in later life,” Madhusmita Misra, MD, MPH, the Fritz Bradley Talbot and Nathan Bill Talbot Professor of Pediatrics at Massachusetts General Hospital and Harvard Medical School, told Healio. “Conditions that result in suboptimal bone accrual during the adolescent and young adult years may result in long-term deficits that are difficult to overcome. Data from studies in adults indicate deleterious effects of sleeve gastrectomy on DXA measures of areal bone density, although effects may be less marked than after gastric bypass. In this study of adolescents and young adults with obesity undergoing sleeve gastrectomy, although DXA measures of bone density decreased over a year, and deleterious effects were noted in several aspects of bone geometry and microarchitecture assessed using high-resolution peripheral quantitative computed tomography, bone strength estimates did not decrease. This appeared to be a consequence of a decrease in porosity associated with an increase in volumetric bone density of cortical bone following surgery.”
Misra and colleagues analyzed data from 44 adolescents and young adults aged 14 to 22 years with moderate to severe obesity who underwent sleeve gastrectomy (n = 22; 16 females) or were followed as controls (n = 22; 16 females), recruited from specialized programs focused on providing lifestyle and surgical options for weight regulation. At baseline and 12 months, participants underwent DXA measurements to assess areal BMD, as well as high-resolution peripheral quantitative CT of the distal radius and tibia to assess bone geometry, microarchitecture and volumetric BMD, and finite element analysis to assess strength estimates for stiffness and failure load. Participants also provided fasting blood samples to measure levels of calcium, phosphorus and vitamin D levels.
During 12 months of follow-up, the surgical group lost an average of 27.2% of body weight compared with 0.1% among controls. There were no reports of fractures in either group during the study.
Compared with controls, those who underwent surgery experienced reductions in femoral neck (mean percent change, –6.9% vs. 0.5%; P = .0007) and total hip areal BMD (mean percent change, –4.7% vs. –0.2%; P = .0004), but changes did not persist after adjustment for 12-month change in BMI.
“In contrast, differences between groups for the 12-month change in whole-body BMD measures became significant after also controlling for BMI change,” the researchers wrote.
At the distal tibia, controls experienced a mean increase in cortical area associated with a decrease in trabecular area, resulting in an increase in cortical thickness that was not observed in the surgery group. The differences persisted after adjusting for 12-month change in BMI. For percent change over time, researchers observed between-group differences for trabecular area among those who underwent surgery vs. controls (mean, –0.3% vs. –1.1%; P = .02), but no changes in cortical area or thickness.
There were no between-group differences in strength estimates during follow-up; however, researchers observed that mean increase in tibial stiffness was lower among those who underwent surgery vs. controls (P = .044), with results persisting after adjustment for 12-month change in BMI.
Misra said further studies are needed to determine the longer-term effects of sleeve gastrectomy and associated weight loss on bone outcomes and whether observed effects over 1 year stabilize or progress over time.
“This study examined factors that may determine changes in bone parameters over 1 year, and identified changes in BMI and lean mass as strongly associated with changes in many bone outcomes,” Misra said. “However, these changes did not account for all observed bone changes, and further studies are necessary to identify other contributors to changes in bone endpoints following surgery. This should help identify future therapeutic targets in these patients.” – by Regina Schaffer
For more information:
Madhusmita Misra, MD, MPH, can be reached at 101 Merrimac St., Suite 615, Boston, MA; email: mmisra@mgh.harvard.edu.
Disclosures: The authors report no relevant financial disclosures.
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Bruno Gualano, PhD
This is a necessary study, as gastric sleeve has become a more common procedure to treat morbid obesity during adolescence, and little is known about the long-term consequences of this treatment.
The finding itself is not surprising. BMD is expected to go down after surgery, primarily as a result of weight loss, as confirmed by the study, and possibly due to other factors, too, such as nutrient malabsorption. The lack of major changes in bone strength is not exactly good news, since the 12-month follow-up was possibly not long enough to detect changes in this parameter.
Bone turnover is higher among youths, and the impact of any intervention able to increase or decrease bone metabolism for this population could be particularly critical. Although the short- to medium-term effects of sleeve gastrectomy among adolescents appear to be promising from a cardiometabolic point of view, much more needs to be understood in the long run, particularly in terms of safety.
One of the most important stimuli for bone accretion during adolescence is physical activity, as healthy bone development requires a proper mechanical load application on the skeleton. Malnutrition is another risk factor for bone loss, especially if it takes place during the critical period of bone maturation. It would be interesting to know whether and how lifestyle can influence long-term outcomes of sleeve gastrectomy performed early in life. Despite the lack of data, I would suggest that being physically active and adopting healthy eating habits is likely more relevant for post-bariatric teens compared with adolescents without excess weight.
While we wait for more research on the long-term effects of sleeve gastrectomy for teens, healthy lifestyle promotion remains the cornerstone for the prevention and treatment of pediatric obesity.
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