Testosterone and sex in older men

Ageing of the “baby boomer” generation foreshadows a future shaped by demographic change, with increasing numbers of older Australians. The large, longitudinal Western Australian Health in Men Study (HIMS) is therefore timely, as it examines the endocrinology of male ageing and predictors of health in community-dwelling older men.1,2 As part of HIMS, my colleagues and I surveyed 3274 men aged 75–95 years in 2008–2009 using a questionnaire that included items on sexual activity.3 Of 2930 men who reported on the importance they attached to sex, 48.8% considered it important, and of the 2783 men who provided data on sexual activity, 30.8% had at least one sexual encounter (defined as any mutually voluntary activity with another person that involves sexual contact, whether or not intercourse or orgasm occurs4) in the previous 12 months.3 Of these older sexually active men, 56.5% were satisfied with the frequency of sex, while 43.0% would have preferred sex more frequently.3 These findings indicate that many older Australian men consider sexual activity important and desirable.

In HIMS, factors that predicted reduced sexual activity were increasing age, osteoporosis, prostate cancer, diabetes, antidepressant use, β-blocker use, and partner’s lack of interest or physical limitations.3 Living with a partner and having a non-English-speaking background were associated with increased sexual activity. Interestingly, a 1 SD increase in testosterone level, measured in blood samples collected in 2001–2004, was associated with a 20% increased likelihood of being sexually active in 2008–2009. Therefore, while older men with lower testosterone levels are likely to report symptoms such as reduced frequency of sexual thoughts and erectile difficulties,5 higher testosterone levels predict sexual activity several years into the future. This raises the question of whether giving exogenous testosterone to induce a comparable increase in circulating total testosterone levels (+ 5.6 nmol/L) would increase the frequency of sexual activity for older men.

Epidemiological studies such as HIMS show that men with testosterone levels in the low-normal range have poorer health outcomes; for example, those with testosterone levels in the lowest quartile (< 11.7 nmol/L) have increased risk of stroke or transient ischaemic attack.6 Lower testosterone levels are associated with mortality in older men.7 Studies of testosterone therapy in older men show favourable effects on body composition, with increased lean mass and bone mineral density and, to an extent, improved muscle strength.8 However, there is no evidence as yet that testosterone therapy reduces cardiovascular events or mortality, or that it increases sexual activity in older men. In fact, administering higher doses of testosterone to older men with limited mobility might result in an excess of adverse cardiovascular events.9 More data are needed to help design optimal studies to clarify the role of testosterone supplementation in ageing men.

In HIMS, the mean serum total testosterone level in 3638 men aged 70–89 years was 15.4 nmol/L (reference range, 8–35 nmol/L), and only a minority would have been classified as having unequivocally low testosterone levels.1 Uncertainty remains around the extent to which lower testosterone levels reflect underlying comorbidity; appropriate testosterone thresholds for the diagnosis of androgen deficiency in older men; and effects of testosterone therapy on cardiovascular risk.8 The current Testosterone Trial (ClinicalTrials.gov identifier NCT00799617) in the United States, due for completion in 2015, is recruiting older men with lower testosterone levels and will examine the effect of transdermal testosterone gel on end points of walking speed, sexual activity, vitality, memory and anaemia correction. So while the question of whether testosterone therapy might protect against cardiovascular events remains unresolved, its impact on sexual activity in the setting of a randomised controlled trial might not be known for another 4 years.

Under these circumstances, the clinical approach to ageing men with symptoms of testosterone deficiency must be prudent, taking both known risks and potential benefits into account.8 Testosterone supplementation could be considered in men who are clearly hypogonadal. Symptoms of androgen deficiency should be assessed, and the diagnosis based on at least two unequivocally low early-morning testosterone levels, preferably assayed using a mass spectrometry-based methodology.10 Men should be counselled as to the risks and benefits of testosterone therapy, and treatment should be accompanied by safety monitoring, including prostate evaluation and monitoring of prostate-specific antigen levels and haematocrit. The anticipated effect of testosterone therapy would be to increase libido, and this should be included in the discussion of benefit and risk.

While higher testosterone levels are associated with sexual activity in older men, non-hormonal factors are also important. HIMS found that increasing age predicted declining sexual activity; after adjusting for this and other covariates, men were four times more likely to be sexually active if they were living with a partner.3 Conversely, they were much less likely to be sexually active if their partner lacked interest in sex or had physical limitations. Medical comorbidities including diabetes and use of antidepressants were also associated with reduced likelihood of being sexually active. Therefore, social and medical factors are key determinants of whether ageing men remain sexually active. The increasing numbers of men transitioning from middle to older age should be encouraged to maintain their personal health and the health of their relationships to maximise their chances of having sex in future years.