The relation between cortisol excretion and fractures in healthy older people: results from the MacArthur studies-Mac.

BACKGROUND

In persons with depression, higher urinary cortisol is associated with lower bone mineral density.

OBJECTIVE

To examine the relation between urinary free cortisol (UFC) and fractures.

SETTING

Community-based samples from Durham, NC, East Boston, MA, and New Haven, CT.

PARTICIPANTS

684 men and women, aged 70 to 79 at baseline, who were part of the MacArthur Study of Successful Aging.

DESIGN

Cohort study. Participants with previous history of fractures at baseline were excluded.

MEASURES: The primary exposure variable was overnight (8:00 p.m. to 8:00 a.m.) UFC (microg/g creatinine) at baseline (1988). Outcomes were self-reported hip, arm, spine, wrist, or other fracture during the follow-up period (1988-1995). Covariates were baseline age, gender, race, body mass index, current physical activity, lower extremity strength, depression subscale of the Hopkins Symptom Checklist, and current use of cigarettes and alcohol.

ANALYSIS: Logistic regression was used to predict the occurrence of incident fractures (1988-1995) as a function of quartiles of baseline UFC. Models were adjusted for age, gender, and race and were also multiply adjusted for the remaining covariates listed above. Gender-stratified models and models that excluded corticosteroid users were also run.

RESULTS

In multiply adjusted models, higher baseline levels of UFC were significantly associated with incident fractures. Odds of fracture (95% Confidence Intervals) for increasing quartiles of baseline UFC, multiply adjusted, were: 2.28 (.91, 5.77); 3.40 (1.33, 8.69); 5.38 (1.68, 17.21). Results were not materially influenced by exclusion of persons using corticosteroids.

CONCLUSIONS

Higher baseline UFC is an independent predictor of future fracture.