Men with enlarged breast tissue that is not caused by extra weight--a condition medically known as gynecomastia--may be at an increased risk of dying before the age of 75, according to the first study of its kind, published in the journal BMJ.

The data suggested that those with a pre-existing risk factor, such as cancer or cardiovascular, lung, or gut disorders prior to diagnosis, are the most vulnerable.

Enlarged breast tissue in men is typically caused by a hormonal imbalance and affects approximately one-third to two-thirds of men, depending on age. It is separate from what is commonly referred to as 'man boobs' (pseudogynecomastia), which is typically associated with overweight or obesity.

The development of gynecomastia can occur at any age but has three distinct peaks across the life course, prompted by pronounced changes in sex hormone levels in the neonatal period, during puberty, and at older ages, note the researchers.

It is most common at older ages, however, as testosterone levels decline and are often accompanied by weight gain, which in turn can make it worse.

Previously published research indicated a link between the condition and a heightened risk of past and future ill health. But it's not clear if gynaecomastia is similarly associated with a heightened risk of death.

To try and find out, the researchers drew on data from Danish national health and population registries: 23,429 men were diagnosed with gynecomastia between January 1, 1995 and 30, 2021. Just over 44 per cent were aged between 19 and 40 at diagnosis.

They were each matched by age and date of diagnosis with 5 randomly selected men without the condition (117,145; the reference group), adding up to a total of 140,574.

The men with gynaecomastia were further divided into 2 groups: those with idiopathic (unknown cause) gynaecomastia (16,253); and those with a known pre-existing condition or taking medication associated with gynaecomastia (7,176).

They were all monitored from the date of study entry to death or the end of June 2021, whichever came first. In all, 12, 676 (9 per cent) men died during the monitoring period.

Among those with gynecomastia, 1093 with the condition of unknown cause and 1501 of those with a pre-existing risk factor died, compared with 10,532 deaths among the men without gynecomastia.

This equates to a 37 per cent higher risk of early death from any cause among those with gynecomastia than among those without the condition.

But when stratified by group, the risk of death was highest in those with a known pre-existing condition, among whom the odds were 75 per cent higher than those with gynaecomastia of unknown cause, among whom the odds were 5 per cent higher.

Pre-existing cancers (74 per cent heightened risk) and circulatory (61 per cent heightened risk), lung (double the risk), and gut diseases (5-fold heightened risk) were associated with the greatest risks. However, neurological disease was associated with a 29 per cent lower risk.

Among individual cancers, those of the digestive tract (39 per cent heightened risk), genitalia (3-fold greater risk), and lymph system (doubling in risk) were associated with the greatest risks.

Among the categories of gut diseases, those of the liver (12-fold heightened risk) and disorders of the gallbladder, biliary tract, and pancreas (14-fold heightened risk) were associated with the greatest risks.

Men with idiopathic gynecomastia weren't generally at greater risk of early death than men in the reference group, except for a cause-specific 2-fold heightened risk of death from liver disease.

This is an observational study, and as such, can't establish causal factors, and the researchers acknowledge that they weren't able to account for potentially influential factors, such as obesity, exposure to endocrine-disrupting chemicals, and steroid use.

By way of an explanation for their findings, the researchers suggest that gynecomastia is strongly intertwined with later health risks and, quite possibly, the drugs used to treat them.

They concluded, "Males diagnosed with gynecomastia are at a 37 per cent higher risk of death, observed mainly in males with a known pre-existing gynecomastia risk factor and not in males with idiopathic gynecomastia. These results should therefore prompt, thorough clinical examination to identify the underlying risk factors."