Exposure to infections in early life does not have long-lasting consequences for later-life survival and reproduction, according to a new study.
Instead, lifestyle during adulthood appears to be a more significant factor in life expectancy, said the researchers from the UK and Finland.
“Early-life disease exposure was not linked to increased risk of death in later life”
They highlighted that 150 years ago, a 20-year-old in the UK could be expected to live to the age of 60, but nowadays it was over 80.
They noted that previous research suggested common childhood diseases, such as smallpox, measles and whooping cough caused long-lasting inflammation, which increased the risk of cardiovascular disease in adulthood and resulted in an early death.
Since the introduction of vaccines and eradication of such diseases, it was thought that fewer people experienced long-lasting inflammation and, as a result, were living longer.
However, the researchers of the new study noted that if this was the case, it would be expected that infections in childhood would be linked to early death from heart disease, stroke and cancer.
But the evolutionary ecologists found no support for the idea that exposure to infections in early life can result in higher mortality risk during adulthood.
They used data on 7,283 men and women studied were born between 1751 and 1850, a period before the introduction of effective medicine and contraception.
Each person was scored on their likely exposure to disease in early life based on child deaths from infections that occurred during their childhood.
If a child was born at a time when a high proportion of children died of infectious diseases, it was assumed that they themselves had higher exposure to disease.
Childhood illness ‘not linked to higher adult mortality’
Researchers analysed how an individual’s early disease exposure was linked to their survival, deaths from cardiovascular disease, and their fertility
Lead researcher Adam Hayward, from the University of Stirling, said: “Our analyses are significant because they show that early-life disease exposure was not linked to increased risk of death in later life.
“It was also not linked to risk of death specifically from heart disease, stroke and cancer and was not related to age at first birth, number of children born, or child survival rate in either men or women,” he said.
“Overall, we found no support for the idea that exposure to infections in early life can have long-lasting consequences for later-life survival and reproduction,” he said.
“Instead, it appears more likely that improved conditions during adulthood, such as healthcare and diet, are responsible for recent increases in adult lifespan,” he added.
The findings have been published in the Proceedings of the National Academy of Sciences.