Birth weight, infant growth foretell physical function in later life

Low birth weight, slow growth during infancy, and either low or high body mass index (BMI) at 11 years of age significantly increase the risk of poor physical functioning at 60 years of age, Finnish and British researchers report.

Using the Short Form 36 scale, the researchers assessed the physical functioning at age 60 of 1,999 people born between 1934 and 1944 who were part of the Helsinki Birth Cohort. Birth and childhood growth data were extracted from medical records. Subjects who weighed less than 2.5 kg at birth had lower physical functioning at a mean age of 61.6 years than subjects who weighed 3.0 kg to 3.5 kg at birth. Lower-functioning subjects also had gained weight more slowly during infancy than their higher-functioning counterparts.

Subjects with low birth weight (<3.0 kg) and either high (>17.5) or low (<16.0) BMI at 11 years of age had an especially high risk of poor physical functioning in older age. The risk was highest for people with birth weight in the lowest third and BMI at 11 years in the highest third of subjects. Associations were independent of childhood socioeconomic status and adult lean body mass, current socioeconomic status, and smoking status.

 The study was published online November 9 in the American Journal of Epidemiology.

“These findings indicate that prenatal and childhood growth set the mark for old-age physical functioning,” the authors conclude. They add that their study is the first to link the combination of low birth weight and high childhood BMI with physical functioning in older age. 

Noting the heightened risk associated with high childhood BMI, the researchers observe that “this piece of information is important as the numbers of obese individuals in all age groups increase and body mass index tends to track through adolescence into adulthood and further increase the risk for old-age disability.”

Possible causes for the association of birth weight and early growth with physical functioning in later life cited by the researchers include permanent impairment of organ development and biologic functioning resulting from a suboptimal prenatal environment. Such an environment also may unfavorably affect body composition by diverting scarce nourishment to vital organs such as the brain at the expense of muscle and other less-important tissue. In addition, lower birth weight increases the incidence of chronic diseases such as diabetes, coronary heart disease, and stroke, the authors note.

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