Risk factors for reduced bone mineral density measurements in milk-allergic patients.

Background: Earlier studies noted that young adults with IgE-mediated cow's milk allergy (IgE-CMA) have significantly lower bone mineral density (BMD) than age- and gender-matched controls. We sought to identify additional risk factors contributing to the low BMD in IgE-CMA patients.

Methods: Postpubertal (defined by Tanner stage V) IgE-CMA patients (n = 78; 16- to 30-year-old females and 17.5- to 30-year-old males) were evaluated prospectively for BMD using a DXA scan, serum values of bone turnover factor, and dietary and lifestyle questionnaires. Patients receiving > 2 short courses of systemic steroid treatments were excluded.

Results: Abnormal BMD measurements (T- or Z-scores < -1.0) of the lumbar vertebrae, femoral neck, or hip were noted in 60 patients, while normal BMD values were present in 18 patients, despite similarly decreased calcium intakes between the groups (P = 0.92). Patients with abnormal BMD were more likely to be asthmatic (P = 0.014), have a lower weight z-score (P = 0.007), have a decreased percent caloric intake derived from fat (P = 0.01), and have an increased carbohydrate intake (P = 0.03), in comparison with the normal-BMD group. Serum values of bone turnover were similar between the groups. On multivariate regression analysis, only asthma significantly (P = 0.006) increased the risk for osteopenia and osteoporosis (OR 38.5, 95% CI 2.8-500). Fitting continuous z-scores into a regression model, both asthma and weight z-score were significant (adjusted r  = 0.272). Asthma was significantly overrepresented in osteopenic and osteoporotic subpopulations while decreased weight only in patients with osteoporosis.

Conclusions: In the context of a low calcium intake, asthma and weight are independent risk factors for decreased BMD in IgE-CMA patients.