Osteoporosis is a common senile condition with major public health impact in both genders of all races. Very little is known about the natural history and etiology of bone loss, and trabecular and cortical volumetric bone mineral density (vBMD) in men, especially in men of African heritage.
This research project was to evaluate age-related patterns and potential correlates for the rate of decline in areal BMD (aBMD) at the proximal femur, and vBMD at the radius and tibia in a cohort of Afro-Caribbean men aged 40 and above from the Tobago Bone Health Study. We also investigated the genetic associations of variants in a gene involved in the bone mineralization process, ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), with bone loss, aBMD and vBMD.
In longitudinal analyses, a significantly greater rate of bone loss was observed in men aged 40-45 than those aged 45-49 and 50-54. Thereafter, the rate of bone loss accelerated with advancing age. The rate of bone loss was also comparable with those observed in Caucasian men. Additionally, we identified low body mass index, weight loss, prostate cancer, and treatment for prostate cancer with androgen deprivation (ADT) as potential determinants for accelerated bone loss.
In cross-sectional analyses of vBMD, we observed an early decline of trabecular vBMD before age 50 and with a slower decline thereafter into 7 th decade. Cortical vMBD, however, appeared to decrease with advancing age in a linear fashion. Correlates of vBMD included weight, diabetes, prostate cancer, ADT, cigarette smoking and bone chewing.
In genetic association study, several variants in the ENPP1 gene were strongly associated with bone loss, aBMD or vBMD. More associations were found with cortical vBMD than with the other phenotypes.
Our findings have important public health relevance as they increase our understanding of vBMD and age-related bone loss in an under-studied population. We have also identified a novel association of ENPP1 gene variants with bone loss and BMD in this population of African heritage. Additional research is needed to better understand the factors related to BMD and bone loss in populations of African ancestry, especially the apparent early loss of bone mass.