Poster Presentation 29th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2019

Small individual-level increase in bone mineral density translated into substantial population-level decrease in fracture incidence: revisiting Goeffrey Rose's axiom (#164)

Thach Tran 1 2 , Jackie R Center 1 2 3 , John A Eisman 1 2 3 4 , Tuan V Nguyen 1 2 5
  1. Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  2. Faculty of Medicine, University of New South Wales, Sydney, Australia
  3. Clinical School, St Vincent's Hospital, Sydney, Australia
  4. School of Medicine Sydney, University of Notre Dame Australia, Sydney, Australia
  5. School of Biomedical Engineering, Centre of Health and Technologies, University of Technology Sydney, Sydney, NSW, Australia

We aimed to test the hypothesis that a modest improvement in bone mineral density (BMD) at the individual level could lead to a large reduction in fracture incidence in the general population. The study involved two cohorts within the Dubbo Osteoporosis Epidemiology Study: the first cohort was recruited between 1989 and 1993 (1213 women, 779 men), and the second cohort in early 2000 (672 women, 358 men), all aged 60+ years at the study entry. Femoral neck BMD was measured by a DXA (GE-Lunar Prodigy). The incidence of fracture after study entry was ascertained by X-ray reports. Changes in BMD and fracture incidence were adjusted for age, body mass index, dietary calcium intakes, physical activity, prior fracture and lifestyle factors.

Femoral neck BMD in the second cohort was significantly higher than that in the first cohort for women (absolute difference: 0.04; 95% CI: 0.02 to 0.05 g/cm2) and men (0.02; -0.001 to 0.04 g/cm2). The prevalence of osteoporosis in women (T-scores≤ -2.5) was significantly lower in the second cohort (12%) than the first cohort (28%; prevalence ratio: 0.47; 95% CI: 0.34 to 0.66). Similar, albeit statistically non-significant, results were noted in men (6% versus 11%; prevalence ratio: 0.56; 95% CI: 0.31 to 1.03). Importantly, the incidence of hip fracture was also lower in the second cohort for women (RR 0.33; 95% CI: 0.19 to 0.58) and men (0.38; 0.15 to 0.99). There was no significant change in non-hip fracture incidence between the two cohorts.

These findings support the Goeffrey Rose's tenet that a small individual-level improvement in a risk factor could lead to a substantial population-level change in incidence. The prevention of fracture should therefore focus on shifting the distribution of risk factors in the population rather than just focus on treating those with high risk of fracture.