Could Exercise Improve Bone Health in Youth With Type 1 Diabetes?

Marlene Busko

September 20, 2022

In a small cross-sectional study of 10- to 16-year-old girls with and without type 1 diabetes, both groups were equally physically active, based on their replies to the bone-specific physical activity questionnaire (BPAQ).

However, among the more sedentary girls (with BPAQ scores below the median), those with type 1 diabetes had worse markers of bone health in imaging tests compared to the girls without diabetes.

"The deleterious effect of [type 1 diabetes] on bone health in girls is most pronounced in those with less weight-bearing activity" the researchers summarize in a poster presented September 9 at the American Society of Bone and Mineral Research (ASBMR) 2022 Annual Meeting.

However, this is early research and further study is needed, the group cautions.

"Ongoing studies with objective measures of physical activity as well as interventional studies will clarify whether increasing physical activity may improve bone health and reduce fracture risk in this vulnerable group," they conclude.

"If you look at the sedentary kids, there's a big discrepancy between the kids who have diabetes and the control kids, and that's if we're looking at radius or tibia or trabecular bone density or estimated failure load," senior author Deborah M. Mitchell, MD, explained to Medscape Medical News at the poster session.

However, "when we look at the kids who are more physically active, we're really not seeing as much difference [in bone health] between the kids with and without diabetes," said Mitchell, a pediatric endocrinologist at Massachusetts General Hospital and assistant professor at Harvard Medical School, Boston, Massachusetts.

But she also acknowledged, "There's all sorts of caveats, including that this is retrospective questionnaire data."

However, if further, rigorous studies confirm these findings, "physical activity is potentially a really effective means of improving bone quality in kids with type 1 diabetes."

"This study suggests that bone-loading physical activity can substantially improve skeletal health in children with [type 1 diabetes] and should provide hope for patients and their families that they can take some action to prevent or mitigate the effects of diabetes on bone," co-author and incoming ASBMR President Mary L. Bouxsein, PhD, told Medscape Medical News in an email.

"We interpret these data as an important reason to advocate for increased time in moderate to vigorous bone-loading activity," said Bouxsein, professor, Department of Orthopedic Surgery, Harvard Medical School, "though the 'dose' in terms of hours per day or episodes per week to promote optimal bone health is still to be determined."

"Ongoing Debate," "Need Stronger Proof"

Asked for comment, Laura K. Bachrach, MD, who was not involved with the research, noted: "Activity benefits the development of bone strength through effects on bone geometry more than 'density,' and conversely, lack of physical activity can compromise gains in cortical bone diameter and thickness."

However, "there is ongoing debate about the impact of type 1 diabetes on bone health and the factor(s) determining risk," Bachrach, a pediatric endocrinologist at Stanford Children's Health, Palo Alto, California, told Medscape Medical News in an email.  

The current findings suggest "that physical activity in adolescent girls provided protection against potential adverse effects of type 1 diabetes," said Bachrach, who spoke about bone fragility in childhood in a video commentary for Medscape in 2021.

Study strengths, she noted, "include the rigor and expertise of the investigators, use of multiple surrogate measures that capture bone geometry/microarchitecture, as well as the inclusion of healthy local controls."  

"The study is limited by the cross-sectional design and subjects who opted, or not, to be active," she added. "Stronger proof of the protective effects of activity on bone health in type 1 diabetes would require a randomized longitudinal intervention study, as alluded to by the authors of the study."

Hypothesis: Those With Type 1 Diabetes Acquire Less Bone Mass in Early 20s

The excess fracture risk in children with type 1 diabetes has been previously reported and is 14% to 35% higher than the fracture risk in children without diabetes, Bouxsein explained. And "between 30% to 50% of kids [with type 1 diabetes] will have a fracture before the age of 18, so the excess fracture risk in diabetes is not clinically obvious," she added.

However, "several lines of evidence strongly suggest that bone mass and microarchitecture at the time of peak bone mass (early 20s) is a major determinant of fracture risk throughout the lifespan," she noted.

"Our hypothesis," Bouxsein said, "is that the metabolic disruptions of diabetes, when they are present during the acquisition of peak bone mass, interfere with optimal bone development, and therefore may contribute to increased fracture risk later in life."

Bachrach agreed that "peak bone strength is achieved by early adulthood, making childhood and adolescence important times to optimize bone health," and that "peak bone strength is a predictor of lifetime risk of osteoporosis."

"The diagnosis of pediatric osteoporosis is made when a child or teen sustains a vertebral fracture or femur fracture with minimal or no trauma," she explained. "The diagnosis can also be made in a pediatric patient with low BMD for age in combination with a history of several long-bone fractures."

Mitchell noted that type 1 diabetes is associated with a higher risk of fractures, which is sixfold in adults. In another study, she said, the group showed that in 10- to 16-year-old girls who've only had diabetes for a few years, "trabecular bone density is lower, they have lower estimated failure load, and longitudinally when we follow them, at least at the radius, we're seeing bone loss at a relatively young age when we wouldn't be expecting to see bone loss."

80 Girls Enrolled, Half Had Type 1 Diabetes

Researchers enrolled 36 girls with type 1 diabetes and 44 girls without type 1 diabetes (controls) who were a mean age of 14.7 years and most (92%) were White. The girls with and without diabetes had similar rates of previous fractures (44% and 51%).

Those with diabetes had been diagnosed at a mean age of 9 years and had had diabetes for a mean of 4.6 years.

Researchers calculated participants' total BPAQ scores based on type, duration, and frequency of bone-loading activities. 

Participants had dual-energy X-ray absorptiometry (DXA) scans to determine areal bone mineral density (BMD) at the total hip, femoral neck, lumbar spine, and whole body less head.

They also had high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal tibia and radius to determine volumetric BMD, bone microarchitecture, and estimated bone strength (calculated using microfinite element analysis).

The two groups had similar total BPAQ scores (57.3 and 64.6), with a median score of 49.

BPAQ scores were positively associated with areal BMD at all sites (whole body, lumbar spine, total hip, femoral neck, and 1/3 radius) and with trabecular BMD and estimated failure load at the distal radius and tibia (P < .05 for all, adjusted for bone age).

Among participants with low physical activity (BPAQ below the median), compared with controls, those with type 1 diabetes had 6.6% lower aerial BMD at the lumbar spine (0.868 vs 0.929 g/cm3; P = .04), 8% lower trabecular volumetric BMD at the distal radius (128.5 vs 156.8 mg/cm3; P = .01), and 12% lower estimated failure load. Results at the distal tibia were similar.

Next Steps

"More observational studies in males and females across a broader age spectrum would be helpful," Bachrach noted. "The 'gold standard' model would be a long-term randomized controlled activity intervention study."

"Further studies are underway [in girls and boys] using objective measures of activity including accelerometry and longitudinal observation to help confirm the findings from the current study," Bouxsein said. "Ultimately, trials of activity interventions in children with [type 1 diabetes] will be the gold standard to determine to what extent physical activity can mitigate bone disease in [type 1 diabetes]," she agreed.

The study authors and Bachrach have reported no relevant financial relationships.

ASBMR 2022 Annual Meeting. Presented September 9, 2022. Abstract FRI-60.  

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