London - British researchers say they have found evidence that male babies who grow slowly in their first year have lower incomes in later life.
The results hold true regardless of the socio-economic status of the child's family, suggesting slow infant growth may be accompanied by hampered brain development, said David Barker, director of the Medical Research Council Epidemiology Unit at Southampton University.
Barker, who presented the findings at the opening in Brighton of the World Congress on the Foetal Origins of Adult Disease, said biological processes linked to poor growth seemed to lead to lifelong impairment of cognitive function.
"What is striking about the findings is that although children who are short at any age up to puberty tend to do less well educationally and have lower incomes in later life, most of the action is in the first year," he said.
Most of the action is in the first year
Barker has pioneered research into how adult diseases begin in the womb, setting out in a recent book, The Best Start In Life: How Diet During Pregnancy Can Affect Babies.
"There are two organs that are not complete when the baby is born - one is the brain and brain development between birth and year one is known to be important," he said.
"The liver is also not complete and the liver sets how the body handles cholesterol, which is probably the link with heart disease."
With researchers at the National Public Health Institute in Helsinki, Barker and colleagues studied 4 630 men born in the Finnish capital between 1934 and 1944.
The height of each man was measured an average of 18 times between birth and age 12, measurements that the researchers linked to records of their level of education and information about income and occupation taken from a 1990 census.
The researchers divided the men into six groups according to their height at age one. Men in the lowest group - under 72 centimetres at one year - earned an average annual salary equivalent to £15 000.
Men in the highest group, longer than 80cm, earned an average of more than £22 000.
"Weight at one year in boys predicts their cognitive function. Boys who grow better between birth and year one have better educational achievements and they make more money when they're 50," Barker said.