However, the authors say the credibility of this association has been unclear; such studies say it is driven by genes, family environment and socioeconomic factors in early life - factors that affect both mortality and young fatherhood.
For their study, Dr. Einiö and colleagues set out to determine whether there may be a causal link between young fatherhood and risk of early death.
To reach their findings, the team analyzed data drawn from the 1950 Finnish census that involved more than 30,500 men who were born between 1940 and 1950. All men had become fathers by the age of 45, and using 1985-2005 mortality data, the men were tracked from the age of 45 until death or until the age of 54.
Fatherhood before age 22 linked to 26% higher death risk in midlife
Around 15% of the men had become fathers by the age of 22, while 29% were fathers by the ages of 22-24, 18% by the ages of 25-26, 19% by the ages of 27-29 and 19% became fathers between the ages of 30 and 44.
The average age of first-time fatherhood was 25-26, according to the study authors, so men in this age group were used as a reference for their findings.
During the 10-year study period, around 1 in 20 fathers died, with around 21% dying from ischemic heart disease and 16% from alcohol-related causes.
Compared with men who became fathers at the ages of 25-26, those who became dads by the age of 22 were found to be at 26% greater risk of death during midlife, while men who had their first child between the ages of 22-24 were at 14% greater risk of death in middle age.
However, men who became first-time fathers between the ages of 30 and 44 were found to be at 25% lower risk of death during midlife, compared with men who had their first child aged 25 or 26.
Becoming a father between the ages of 27 and 29 appeared to have no influence on midlife mortality.
These findings remained after accounting for influential factors, such as fathers' educational attainment, area of residence, marital status and number of children.
The team also analyzed the mortality risk of 1,124 brothers who were fathers. They found - compared with siblings who became fathers by the age of 25 or 26 - those who had their first child by the age of 22 were around 73% more likely to die during middle age, while those who became fathers aged 22-24 were at 63% greater risk of death during midlife.
Brothers who became fathers between the ages of 30 and 44, however, were found to be at 22% lower risk of death during middle age, compared with those who had their first child aged 25-26.
These results remained even after the researchers accounted for brothers' year of birth, educational attainment, marital status, area of residence, number of children and shared circumstances in early life.
Findings indicate a causal link between young fatherhood and early death
The researchers say their findings suggest a likely causal link between young fatherhood and greater risk of death in middle age. "The association was not explained by unobserved early-life characteristics shared by brothers or by certain adulthood characteristics known to be associated both with fertility timing and mortality," they note.
While the team is unable to pinpoint the exact mechanisms behind the findings observed in this study, Dr. Einiö told Medical News Today that it may be down to the stress of fatherhood at such a young age.
"We know based on other studies that many pregnancies were unplanned and young parents often decided to form a new household at that time," she said. "It is possible that suddenly taking on the combined role of father and breadwinner may have caused considerable psychological and economic stress for a young man not ready for his new role. Of course, not all the children of young fathers were unplanned, but many were."
As such, Dr. Einiö told MNT it is important that men who become fathers at a young age take care of themselves:
"Despite the responsibilities of fatherhood, young fathers, who reside with their child, should find the time for good health behaviors, such as physical exercise to improve their future health."
Another fatherhood study published last month found men gained an average of 4.4 Ib in weight after their first child, while over the same study period, the average man who did not have a child lost around 1.4 Ib in weight.
