Longitudinal changes in BMD and bone geometry in a population-based study

Abstract

We prospectively examined vBMD and structural bone parameters assessed by QCT among participants of the InCHIANTI study over a 6-yr follow-up. Periosteal apposition occurred both in men and women. Endocortical resorption causes bone loss in older women despite periosteal apposition.

Introduction: To address the hypothesis that age-related changes in BMD and bone geometry may be different in men and women, we prospectively examined volumetric BMD (vBMD) and structural bone parameters assessed by QCT among participants of the InCHIANTI study over a 6-yr follow-up.

Materials and methods: Three hundred forty-five men and 464 women 21-102 yr of age from the InCHIANTI study, a population-based study in Tuscany, Italy, were included. Tibial QCT bone parameters were measured at enrollment (1998-2000) and at 3- (2001-2003) and 6-yr (2004-2006) follow-ups.

Results: Periosteal apposition occurred both in men and women. The annual rate of bone periosteal apposition was higher in younger than in older men, whereas in women, the rate of apposition was homogenous across age groups. The age-related medullary expansion, expression of endocortical resorption, was significantly higher in women compared with men. In women, but not in men, accelerated endocortical resorption not sufficiently balanced by periosteal apposition caused accelerated loss in cortical bone mass. The cross-sectional moment of inertia decreased progressively over the life span in both sexes.

Conclusions: Endocortical resorption causes bone loss in older women despite periosteal apposition. Obtaining a balance between endocortical resorption and periosteal apposition should be the target for interventions aimed to decrease bone loss and prevent osteoporosis in older women.

FIG. 1

(Right panels) Longitudinal changes in total BMD (vBMD) (A), trabecular BMD (vBMDt) (B), total bone area (tCSA) (C), medullary bone area (D), and cortical bone area (E) during the 6-yr follow-up according to baseline age decade, from 20 to 100 yr, in men and women. (Left panels) Age-related trajectories of the bone parameters during life span estimates from the cross-sectional (red line) and longitudinal data (blue line) and their 95% CIs (black lines).

FIG. 2

Age-related trajectories of the cross-sectional moment of inertia at 38% during life span estimates from the cross-sectional (red line) and longitudinal data (blue line) and their 95% CIs (black lines).

FIG. 3

Hypothetical schematic model of the changes in bone geometry parameters, at 38% of the tibia level, during life span in men and women. The rate of endocortical reabsorption is much higher in women than in men and considerably exceeds the effect of periosteal apposition, which assumes a different rate in men and women with aging. In fact, whereas periosteal apposition is higher in younger men than in old men, in women, it is higher in older women than young women.