Weight-bearing physical activity, calcium intake, systemic glucocorticoids, chronic inflammation, and body constitution as determinants of lumbar and femoral bone mineral in juvenile chronic arthritis.

The associations between the lumbar and femoral bone mineral and several body constitutional, lifestyle, and disease related variables were studied in 111 children with juvenile chronic arthritis (JCA) by factor and multiple linear regression analyses. In addition to the measurement of bone mineral density (BMD), bone width and bone mineral volumetric density (BMDvol) were determined by dual-x-ray absorptiometry (DXA). Factor analysis of 13 explanatory variables yielded six non-correlating factors, named as body size, physical activity, calcium intake, glucocorticoids, disease duration, and disease activity. These six factors were used as new variables to explain BMD, BMDvol, and bone width by multiple linear regression analyses. These showed body size, physical activity, and calcium intake as significant positive and disease activity and glucocorticoids as significant negative determinants of BMD in JCA. The analyses revealed also considerable differences in the relationships between factors and BM Dvol or bone width.