Birth weight and childhood overweight - exploring parental influences and future risk of coronary heart disease

Abstract

Overweight and obesity now affect individuals of all ages in all parts of the world. Obesity leads to individual suffering as well as increased risk of future disease and premature death from several causes, among which coronary heart disease (CHD) is the most common. The disease pathway to increased risk of CHD likely begins already before conception and may be further influenced by later weight development during childhood and adolescence. There is a need for increased understanding of how parental factors such as smoking and maternal weight status, and family socioeconomic position influence developmental weight, as well as how weight development from birth up to young adult age influence the risk of CHD. This thesis applies a life course perspective on these associations through four cohort studies. Low family socioeconomic position is a well-established risk factor for childhood obesity. However, the separate influences of parental education and family income are not known. Using a cohort of 3,030 children born 1998-2002, we found that low parental education was a risk factor for developing obesity at eight years of age, independent of family income and maternal body mass index (BMI). (Paper I) Smoking and obesity at the start of pregnancy are associated with birth weight and future adverse metabolic risk profile of the child. However, their role in late adolescence, several years before start of pregnancy, for later pregnancy outcomes, have not yet been explored. In a cohort of 1,256 mother-and-child-pairs, we found that smoking and BMI at 19 years of age were not associated with the birth weight of the first child. (Paper II) Low birth weight is a well-studied risk factor for adult CHD, but studies are scarce regarding how this risk is affected by BMI development during childhood and adolescence. Using a cohort of 35,659 men born 1945-1961, we found that a birth weight below 3.6 kg was associated with increased risk of CHD and this risk was further augmented for men who had overweight in young adult age. (Paper III) Childhood overweight and obesity have been linked to increased risk of adult CHD. We studied a cohort of 103,232 men and women born 1945-1968 and found that this risk was normalized for children who had remission of overweight before young adult age. (Paper IV) The findings in this thesis identify several modifiable risk factors important for future risk of CHD. The results clearly highlight the importance of prevention, early identification, and treatment of childhood overweight and obesity.