There were a total of 22 deaths in Irish prisons last year.
Over the last decade there have been a total of 129 deaths in prisons in the Republic, and 44 recorded deaths in prisons in the North.
The new data comes from the Belfast-based website The Detail - which collected data from prisons across the island of Ireland.
Among the findings were that nearly one-third of inmates who died in the Republic were finishing their sentences in the community on temporary release.
Data from The Inspector of Prisons also found that out of 62 prisoners died since 2012, 22 were suspected suicides, 19 were drug-related, five were homicides and 28 were due to natural causes.
Out of the 62 deaths subject to reports by the Inspector of Prisons since 2012, 39 were of prisoners under 40.
Sixteen were in their 20s, while 23 were in their 30s. Seven inmates were in their 40s, eight were in their 50s and five in their 60s.
Two of the deceased were in their 70s, while one man was 82 when he died.
A spokesman for the Irish Prison Service said: "It should be borne in mind that deaths in custody can occur for a number of reasons including age or underlying medical issues on committal leading to death by natural causes, deaths by drugs overdose, or deaths by suicide."
