Population variation in age-related decline in male salivary testosterone

Department of Anthropology, Harvard University, Cambridge, MA, 2 Department of Anthropology, Yale University, New Haven, CT, USA, 3 Department of Anthropology, University College London, London, UK, 4 Department of Anthropology, Boston University, Boston, MA, USA, 5 Department of Anthropology, Durham University, Durham, UK and 6 Department of Anthropology, University of New Mexico, Albuquerque, NM, USA

Although formerly controversial, an age-related decline in free and bioavailable testosterone in healthy males is now a frequently reported pattern in Western populations (Ferrini and Barrett-Connor, 1998Go; Vermeulen et al., 1999Go; Harman et al., 2001Go). Age-related declines in testosterone levels in males have been associated with changes in body composition, including increases in fat mass, decreases in muscle mass, and decreases in bone mineral density (Denti et al., 1999Go; Vermeulen et al., 1999Go; Kenny et al., 2000Go; van den Beld et al., 2000Go). Reflecting these linkages to body composition, age-related declines in male testosterone are also associated with elevated risk of type II diabetes (Stellato et al., 2000Go; Haffner et al., 1996Go), coronary heart disease (Simon et al., 1997Go; De Pergola et al., 1997Go), ischemic stroke (Jeppesen et al., 1996Go) and osteoporosis (Francis, 1999Go; Snyder et al., 1999aGo). Low testosterone levels in older men are also associated with low libido, erectile dysfunction, and depression (Barrett-Connor et al., 1999Go; Schweiger et al., 1999Go; Wang et al., 2000Go). On the other hand, high testosterone levels have been associated with elevated risk and progress of prostate cancer (Crawford, 1992Go; van Tinteren and Dasio, 1993Go). Testosterone supplementation of older men has been shown to result in increases in lean-body mass, decreases in fat mass, increases in bone mineral density, and improvements in mood and sexual function (Bhasin and Tenover, 1997Go; Snyder et al., 1999aGo,bGo; Winters, 1999Go).

Despite evidence of its clinical importance, relatively little is known about population variation in age patterns of testosterone. This contrasts strikingly with the increasing awareness of population variation in female ovarian steroid profiles and its relationship to disease risk (Ellison et al., 1993Go; O'Rourke and Ellison, 1993Go; Ellison, 1999Go; Jasienska et al., 2000Go; Jasienska and Thune, 2001Go). There are scattered reports of male testosterone levels from non-Western, non-clinical populations, but the comparability of these data is limited by differences in sample collection, handling, and assay procedures (Guerra-Garcia et al., 1969Go; Smith et al., 1975Go; Christiansen, 1991aGo,bGo; Beall et al., 1992Go; Campbell, 1994Go).

This report presents data on age variation in male salivary testosterone values from four populations spanning broad genetic, ecological, and life style differences. Similar studies on human growth hormone and their relation to age have also been done. All the samples were collected using the same protocols and were assayed in the same laboratory using consistent methods. The data are used for a preliminary test of the hypothesis that significant population variation exists in the pattern of age-related decline in male testosterone. By analogy with findings for women (Ellison et al., 1993Go), we expect that non-Western males will have lower levels of testosterone in adulthood and slower rates of decline in testosterone with increasing age.