Coronary heart disease (CHD) risk was lowest for women and men who had two children compared to those with more than two children, according to Debbie A. Lawlor, M.P.H., lead author of the study.
In both men and women there was a "J-shaped" association between the number of children and prevalence of CHD. Those with one child or less had a higher risk compared to those with two children; however, the risk increased with each additional child after the second one. Among women with more than two children, risk for CHD increased by 30 percent with each additional child. For men with more than two children, the risk increased by 12 percent with each additional child.
Researchers studied 4,286 women and 4,252 men aged 60 to 79 who had from zero to five or more children. They found that with increasing numbers of children, both parents were more likely to be obese. Mothers of more than two children were also more likely to have evidence of insulin resistance, elevated blood sugar and diabetes, as well as low levels of high-density lipoprotein (HDL – the so called "good cholesterol") and increased triglycerides – all of which show a gradient with increasing numbers of children. Adjusting for obesity and other risk factors weakened the association between number of children and CHD risk in fathers, but a link still remained among mothers.
"Parents of large families tend to be poorer and also have less healthy lifestyles – which explains some of their increased CHD risk," says Lawlor, a lecturer in the department of social medicine, University of Bristol, Bristol, U.K.
She says the different results for fathers and mothers suggest that multiple pregnancies also have a specific adverse metabolic effect on women resulting in insulin resistance, which is an important risk factor for CHD.
"These results reinforce the need to encourage mothers and fathers of several children to maintain a healthy weight and lifestyle which may reduce the chances of developing obesity and CHD in later life," she says. "In addition, careful screening and control of metabolic abnormalities during pregnancy should be undertaken in women receiving prenatal care, particularly among women who have had a number of earlier pregnancies."
Co-authors are Jonathan R. Emberson; Shah Ebrahim; Peter Whincup, Ph.D.; Goya Wannamethee, Ph.D.; Mary Walker; and George Davey Smith.
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