Teenagers who drink a lot of alcohol dramatically increase their risk of deadly prostate cancer later in life, research suggests.
A study found that 15 to 19-year-olds who consumed at least seven drinks per week tripled their chances of being diagnosed with "high-grade" aggressive prostate cancer.
The research was led by Dubliner Dr Emma Allott during her time at Gillings School of Global Public Health, in the University of North Carolina at Chapel Hill in the US.
Dr Allott said: "The prostate is an organ that grows rapidly during puberty, so it's potentially more susceptible to carcinogenic exposure during the adolescent years.
"For this reason, we wanted to investigate if heavy alcohol consumption in early life was associated with the aggressiveness of prostate cancer later."
Dr Allott's team recruited 650 ex-servicemen aged 49 to 89 undergoing biopsy tests for prostate cancer.
The men completed questionnaires which assessed their weekly alcohol consumption during each decade of life.
Heavy drinking at ages 15 to 19 had no effect on general prostate cancer risk.
But compared with non-drinkers, consumption of at least seven alcohol drinks per week over this age period tripled the likelihood of having high-grade prostate cancer.
A similar level of alcohol consumption between the ages of 40 to 49 led to a 3.64-fold greater chance of being diagnosed with the potentially deadly disease.
However there was no significant correlation between current alcohol consumption and high-grade cancer risk.
Over the course of a lifetime, men who drank the most alcohol were three times more likely to be diagnosed with high-grade prostate cancer.
While low-grade prostate cancer often causes little harm, aggressive versions of the disease known as "tigers" can quickly spread and prove fatal without radical treatment.
Dr Allott said: "Our results may explain why previous evidence linking alcohol intake and prostate cancer has been somewhat mixed.
"It's possible that the effect of alcohol comes from a lifetime intake, or from intake earlier in life, rather than alcohol patterns around the time of diagnosis of prostate cancer."
The authors pointed out that men who consumed a lot of alcohol early in life typically continued to drink heavily throughout life.
For this reason, it was difficult to separate the effects of cumulative exposure to alcohol and early-life drinking habits.
Dr Allott is the Irish Cancer Society’s John Fitzpatrick Research Fellow at Trinity College, Dublin. The fellowship was established by the Irish Cancer Society, the Dana-Farber Cancer Institute and Harvard T.H. Chan School of Public Health to fund an Irish scientist or clinician to undertake high-quality research into prostate cancer.
It is named in memory of Professor John Fitzpatrick, the former Head of Research at the Irish Cancer Society, marking his significant international contribution to prostate cancer research.