Change in bone mineral density as a function of age in women and men and association with the use of antiresorptive agents

Abstract

Background: Measurement of bone mineral density is the most common method of diagnosing and assessing osteoporosis. We sought to estimate the average rate of change in bone mineral density as a function of age among Canadians aged 25-85, stratified by sex and use of antiresorptive agents.

Methods: We examined a longitudinal cohort of 9423 participants. We measured the bone mineral density in the lumbar spine, total hip and femoral neck at baseline in 1995-1997, and at 3-year (participants aged 40-60 years only) and 5-year follow-up visits. We used the measurements to compute individual rates of change.

Results: Bone loss in all 3 skeletal sites began among women at age 40-44. Bone loss was particularly rapid in the total hip and was greatest among women aged 50-54 who were transitioning from premenopause to postmenopause, with a change from baseline of -6.8% (95% confidence interval [CI] -7.5% to -4.9%) over 5 years. The rate of decline, particularly in the total hip, increased again among women older than 70 years. Bone loss in all 3 skeletal sites began at an earlier age (25-39) among men than among women. The rate of decline of bone density in the total hip was nearly constant among men 35 and older and then increased among men older than 65. Use of antiresorptive agents was associated with attenuated bone loss in both sexes among participants aged 50-79.

Interpretation: The period of accelerated loss of bone mineral density in the hip bones occurring among women and men older than 65 may be an important contributor to the increased incidence of hip fracture among patients in that age group. The extent of bone loss that we observed in both sexes indicates that, in the absence of additional risk factors or therapy, repeat testing of bone mineral density to diagnose osteoporosis could be delayed to every 5 years.

Figure 1: Rate of change in bone mineral density in the lumbar spine (top) and total hip (bottom) as a function of age among women using antiresorptive agents (hormone replacement therapy or bisphosphonates). Bone mineral density is expressed as grams per square centimetre per year. Values above 0 indicate increased bone mineral density, and values below 0 indicate bone loss.

Figure 2: Rate of change of bone density as a function of age among women not using (top) or using (middle) antiresorptive agents, and rate of change of bone density in the total hip among women not using antiresorptive agents by menopausal status (bottom). Values above 0 indicate increased bone density, and values below 0 indicate bone loss.

Figure 3: Rate of change of bone density as a function of age among men not using (top) or using (bottom) antiresorptive agents. Values above 0 indicate increased bone density, and values below 0 indicate bone loss.