Many years ago, at the conclusion of a talk I gave on bone health in teens with anorexia nervosa, I was approached by a colleague, Ann Neumeyer, MD, medical director of the Lurie Center for Autism at Massachusetts General Hospital, who asked about bone health in children with autism spectrum disorder (ASD).
When I explained that there was little information about bone health in this patient population, she suggested that we learn and investigate together. Ann explained that she had observed that some of her patients with ASD had suffered fractures with minimal trauma, raising her concern about their bone health.
This was the beginning of a partnership that led us down the path of many grant submissions, some of which were funded and others that were not, to explore and investigate bone outcomes in children with ASD.
Over the years it has become very clear that these patients are at high risk for low bone density at multiple sites. This applies to prepubertal children as well as older children and adolescents. One study showed that 28% and 33% of children with ASD 8-14 years old had very low bone density (Z-scores of ≤ -2) at the spine and hip, respectively, compared with 0% of typically developing controls.
Studies that have used sophisticated imaging techniques to determine bone strength have shown that it is lower at the forearm and lower leg in children with ASD vs neurotypical children.
These findings are of particular concern during the childhood and teenage years when bone is typically accrued at a rapid rate. A normal rate of bone accrual at this time of life is essential for optimal bone health in later life. While children with ASD gain bone mass at a similar rate as neurotypical controls, they start at a deficit and seem unable to "catch up."
Further, people with ASD are more prone to certain kinds of fracture than those without the condition. For example, both children and adults with ASD have a high risk for hip fracture, while adult women with ASD have a higher risk for forearm and spine fractures. There is some protection against forearm fractures in children and adult men, probably because of markedly lower levels of physical activity, which would reduce fall risk.
Many of Ann's patients with ASD had unusual or restricted diets, low levels of physical activity, and were on multiple medications. We have since learned that some factors that contribute to low bone density in ASD include lower levels of weight-bearing physical activity; lower muscle mass; low muscle tone; suboptimal dietary calcium and vitamin D intake; lower vitamin D levels; higher levels of the hormone cortisol, which has deleterious effects on bone; and use of medications that can lower bone density.
In order to mitigate the risk for low bone density and fractures, it is important to optimize physical activity while considering the child's ability to safely engage in weight-bearing sports.
High-impact sports like gymnastics and jumping, or cross-impact sports like soccer, basketball, field hockey, and lacrosse, are particularly useful in this context, but many patients with ASD are not able to easily engage in typical team sports.
For such children, a prescribed amount of time spent walking, as well as weight and resistance training, could be helpful. The latter would also help increase muscle mass, a key modulator of bone health.
Other strategies include ensuring sufficient intake of calcium and vitamin D through diet and supplements. This can be a particular challenge for children with ASD on specialized diets, such as a gluten-free or dairy-free diets, which are deficient in calcium and vitamin D. Healthcare providers should check for intake of dairy and dairy products, as well as serum vitamin D levels, and prescribe supplements as needed.
All children should get at least 600 IUs of vitamin D and 1000-1300 mg of elemental calcium daily. That said, many with ASD need much higher quantities of vitamin D (1000-4000 IUs or more) to maintain levels in the normal range. This is particularly true for dark-skinned children and children with obesity, as well as those who have medical disorders that cause malabsorption.
Higher cortisol levels in the ASD patient population are harder to manage. Efforts to ease anxiety and depression may help reduce cortisol levels. Medications such as protein pump inhibitors and glucocorticosteroids can compromise bone health.
In addition, certain antipsychotics can cause marked elevations in prolactin which, in turn, can lower levels of estrogen and testosterone, which are very important for bone health. In such cases, the clinician should consider switching patients to a different, less detrimental medication or adjust the current medication so that patients receive the lowest possible effective dose.
Obesity is associated with increased fracture risk and with suboptimal bone accrual during childhood, so ensuring a healthy diet is important. This includes avoiding sugary beverages and reducing intake of processed food and juice.
Sometimes, particularly when a child has low bone density and a history of several low-trauma fractures, medications such as bisphosphonates should be considered to increase bone density.
Above all, as physicians who manage ASD, it is essential that we raise awareness about bone health among our colleagues, patients, and their families to help mitigate fracture risk.
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Cite this: Autism and Bone Health: What You Need to Know - Medscape - May 04, 2023.