A longitudinal study of dehydroepiandrosterone sulphate (DHEAS) change in older men and women: the Rancho Bernardo Study.

Objective: To examine the age-related and sex-specific rates and determinants of change in endogenous dehydroepiandrosterone sulphate (DHEAS) levels in older community-dwelling adults, taking into account regression to the mean.
Design: Prospective cohort study from Rancho Bernardo, California, USA.
Methods: Plasma for DHEAS was collected at baseline and 10-14 years later from 242 men and 207 postmenopausal women (age range, 60-77 years), who were not taking hormone therapy or corticosteroids. Age-related and sex-specific changes in DHEAS were calculated according to four different definitions of change: absolute change, annual percentage change, change exceeding 10% of baseline and change exceeding that expected from statistical regression to the mean. Determinants of DHEAS change were assessed using regression analyses.
Results: Baseline DHEAS levels were higher for men than women (age-adjusted means, 1.37+/-0.73 microg/ml (3.72+/-1.98 micromol/l) vs 0.73+/-0.48 microg/ml (1.98+/-1.30 micromol/l) respectively, P<0.0001), with more pronounced declines observed in men (-4.0%/year) compared with women (-2.1%/year; P<0.001). Some 28% of women and 5% of men had DHEAS levels that increased or stayed the same according to a 10% definition of change. When regression to the mean artifact was accounted for, only 15% of women and 5% of men showed true increases in DHEAS. In both sexes, baseline DHEAS levels accounted for three-quarters of the variability in absolute DHEAS change over time, with higher baseline levels resulting in greater loss. Sex, baseline weight, age and smoking status were significantly associated with DHEAS change in univariate models; only sex remained independently associated with DHEAS change in multivariate analyses, with men showing greater annual declines than women (estimated coefficient=0.006, P=0.008).
Conclusion: In this sample, over 30% of the observed changes in DHEAS could be attributed to regression to the mean. Potential underlying mechanisms of change in DHEAS levels, and sex differences, are discussed.