Men's average testosterone levels have halved over 50 years, scientists warn of health crisis

Men's average testosterone levels have decreased by 54% over the past 50 years, according to researchers presenting findings on Tuesday at the annual meeting of the European Society of Human Reproduction and Embryology in London. The alarming trend raises concerns about a potential male fertility crisis, attributed to factors such as obesity, diabetes, and environmental influences.

Significant Decline in Male Testosterone Levels

The meta-analysis examined data from over 100,000 men, spanning from 1972 to 2019. Prof. Hagai Levine from the Hebrew University-Hadassah Braun School of Public Health emphasized the seriousness of the findings, stating, "We saw an over 50% decline in total testosterone over this time period." This consistent decline averages more than 1% each year, indicating a strong trend rather than a statistical error.

Previous studies by the same research team have also highlighted a steep decline in sperm counts, further fueling discussions around male reproductive health. U.S. Health Secretary Robert F. Kennedy Jr. has referred to the decline in male fertility as an "existential problem." However, these assertions have sparked debate within the scientific community.

Factors Contributing to Testosterone Decline

Prof. Channa Jayasena from Imperial College London remarked that the recent observations on testosterone serve as "an important reality check." The relationship between testosterone and overall health is complex; testosterone influences sperm production, muscle mass, bone density, and mood. Factors like obesity can lead to reduced testosterone levels, as excess body fat converts testosterone into estrogen.

Levine noted that while obesity and metabolic syndrome could explain a significant portion of the decline, environmental factors also merit consideration. The meta-analysis included data from six longitudinal studies, which collectively revealed a 54% drop in testosterone levels, with the decline appearing to accelerate post-2000.

The Role of Environmental Factors

Although the studies controlled for age, the impact of confounding factors like obesity was not fully accounted for. Levine estimated that obesity and metabolic syndrome might explain 25% to 50% of the decline. Jayasena cautioned that attributing the decline solely to obesity and diabetes could be premature, urging further investigation into potential environmental influences.

Levine advocated for a precautionary approach, stating, "The level of certainty that we need is not 95%. We should find better ways to prevent exposure of the general public to hazardous chemicals." Concerns have arisen over the promotion of testosterone supplements, as these can suppress sperm production, complicating treatment options for men with low testosterone.

• 54% decline in testosterone levels from 1972 to 2019
• Data analyzed from 118,593 individuals
• Decline appears to accelerate after 2000
• Obesity and diabetes linked to lower testosterone
• Environmental factors remain under investigation