The decline in testosterone levels among older men remains a subject of debate. While some cross-sectional and longitudinal studies have reported a decrease in testosterone with advancing age, others have not observed this trend. In this study, we aimed to evaluate testosterone levels and identify predictors of low testosterone in an age-stratified cohort of men.

From January 2016 to June 2022, a cohort of men receiving routine care at a primary care center was prospectively analyzed. Participants were stratified into age groups: 45-64 years (middle-aged), 65-74 years (young-old), 75-84 years (middle-old), and ≥85 years (oldest-old). Comprehensive clinical and laboratory assessments were conducted, including waist circumference, glucose levels, triglycerides, HDL cholesterol, and total testosterone. Low testosterone was defined as levels below 300ng/dL. Metabolic syndrome was diagnosed in accordance with established diagnostic criteria.

The study included 3.489 subjects across age groups. Median testosterone levels were similar across all age groups. The prevalence of low testosterone was around 20% in all groups and did not significantly vary with age. Obesity, as indicated by increased waist circumference (WC) >102 cm, was strongly associated with low testosterone. The prevalence of low testosterone increased from 8% in those with WC≤93cm to 44% in those with WC≥110cm.

This study highlights the significant association between low testosterone levels and obesity, reinforcing the importance of addressing comorbidities in testosterone decline.