How accurate is self reported birth weight among the elderly?

The eVect of early life influences on adult health is a central topic in current epidemiological research. For instance, growth and development in utero and in infancy have been linked to cardiovascular disease. In empirical research in this field, birth weight is often used as an indicator of health and nutrition in utero. There are two main sources of birthweight data: birth records and the memories of subjects or their families, or both. Where the subjects are elderly, however, early birth records with recorded birth weights are not easy to find and the recovery rate is generally low. Where there are no surviving birth records with birthweight data and where the subject’s parents cannot be asked, the subject’s own testimony is the only possible source of such data. But can self reported birth weight be relied upon in the absence of data from clinical or administrative sources? Birth weights recalled by mothers have been found to correlate highly with those found in oYcial records. The accuracy of self reported birth weights, however, is less certain—some studies have reported a poor degree of correspondence between birth weights recorded in oYcial records and self reported birth weights. Other researchers have found that birth weights from these two sources correlate reasonably well. Most investigations of the validity of self reported birth weight have typically used subjects who were middle aged or younger. In the investigation reported here, we use data collected in a study of childhood diet and health and disease in later life to estimate the accuracy of the self reported birth weights for an older age group of 57 to 77 year old women and men. It is important to note that the results reported are only relevant to studies involving the use of birthweight recall in older age groups. The older age of the subjects means that the probability of them having access to their mother’s recall or being able to remember reports from their mothers is lower than younger age groups. In addition, for historical reasons, the likelihood of finding surviving birth or maternity records for a particular person tends to fall with that person’s age.