title: Genetic and environmental determinants of volumetric and areal BMD in multi-generational families of African ancestry: the Tobago Family Health Study.
abstract: BMD is higher and fracture risk is lower among individuals of African versus European descent, but little is known about the genetic architecture of BMD in the former group. Heritabilities of areal and volumetric BMD were moderate in our large families of African descent but differed for trabecular and cortical BMD.
  
  
  BACKGROUND
  Populations of African ancestry have lower osteoporotic fracture risk and higher BMD than other ethnic groups. However, there is a paucity of information regarding the genetic and environmental influences on bone health among populations of African heritage.
  
  
  METHODS
  We dissected the genetic architecture of areal BMD measured by DXA at the proximal femur, lumbar spine, and whole body and volumetric BMD measured by pQCT at the distal and proximal radius and tibia in 283 women and 188 men > or =18 years of age (mean, 43 years) from eight multigenerational Afro-Caribbean families (mean family size > 50). Using quantitative genetic methods, we estimated the residual heritability and the effects of anthropometric, demographic, lifestyle, and medical variables on areal and volumetric BMD.
  
  
  RESULTS
  Compared with U.S. non-Hispanic blacks and whites, areal BMD at the femoral neck was highest in the Afro-Caribbean men and women at all ages. Trabecular volumetric BMD decreased linearly with increasing age, whereas cortical volumetric BMD did not decrease until age 40-49, especially in women. Anthropometric, lifestyle, and medical factors accounted for 12-32% of the variation in areal and volumetric BMD, and residual heritabilities (range, 0.23-0.52) were similar to those reported in other ethnic groups. Heritability of cortical BMD was substantially lower than that of areal or trabecular volumetric BMD, although the measured covariates accounted for a similar proportion of the total phenotypic variation.
  
  
  CONCLUSIONS
  Our study is the first comprehensive genetic epidemiologic analysis of volumetric BMD measured by QCT and the first analysis of these traits in extended families of African descent. Genes account for as much or more of the total variation in areal and volumetric BMD than do environmental factors, but these effects seem to differ for trabecular and cortical bone.
authors.affiliation: Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA 15261, USA. xiaojing.wang@hgen.pitt.edu
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Wang
authors.forename: Candace M
authors.initials: CM
authors.lastname: Kammerer
authors.forename: Victor W
authors.initials: VW
authors.lastname: Wheeler
authors.forename: Alan L
authors.initials: AL
authors.lastname: Patrick
authors.forename: Clareann H
authors.initials: CH
authors.lastname: Bunker
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Zmuda
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D044383:Black People / Q000235:genetics*; D001827:Body Height; D001835:Body Weight; D015519:Bone Density / Q000235:genetics*; D004777:Environment; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D012098:Reproduction; D012727:Sex Characteristics; D014300:Trinidad and Tobago