In this population of African American women, both parental education and current education were inversely associated with adult weight gain and with risk of obesity in adulthood. Current education had a stronger effect than parental education, indicated by the fact that when parental and current education were modeled together, effect estimates associated with parental education were more attenuated than the estimates associated with current education. Lifecourse analyses indicated that women were able to overcome the adverse effects of low parental education on weight gain and obesity risk by improving their current educational level to college graduate. Improvement of educational current level only to some college had little effect on weight gain and obesity risk.
Control for childhood influences in the analyses resulted in little change in the relative weight gain estimates, suggesting that they had little mediating or confounding influence on the associations of parental, current, and lifecourse education with weight gain. On the other hand, the addition of adult factors to the models attenuated the effects of education on weight gain, suggesting that the adult behaviors are part of the pathway by which childhood and current education influence weight gain. The relative risks of obesity were less altered by covariate control.
Participant education had the same pattern of effects on weight gain and obesity risk as did current (self/spouse) education, but the magnitudes of the effects were smaller, suggesting that a variable that selects highest level of self/spouse education better captures the educational and socioeconomic environment of the adult woman.
Studies of lifecourse SES and weight vary widely in terms of study population, study design, classification of childhood and adult SES, and quantification of weight outcomes, making direct comparison difficult. Our results are consistent with several studies that show a deleterious influence of low childhood SES and of low adult SES on weight and obesity later in life.1-3
Most studies that considered childhood and adult SES together found that childhood SES had a stronger influence on adult weight. These include the British Whitehall II study,21,22
the Australian Longitudinal Study on Women’s Health,13
and the Helsinki Health study.7
However, the European studies had few if any black participants and results are of uncertain relevance to African American women.
Several U.S. studies have included black and white participants but have reported only combined results. In the Monitoring the Future study,9
childhood SES had a stronger influence on weight gain than current education. In that study, however, the highest level of education considered was high school graduate. In the National Longitudinal Study of Adolescent Health,14
improvement in SES, even to the highest level, overcame some, but not all, of the disadvantage conferred by low childhood SES. In contrast, in BWHS, improvement in education to the level of college graduate appeared to obviate the effects of low parental education. In the former study, the metrics of childhood and adult SES included information on household income, use of public assistance, social capital, and other variables in addition to education and thus was a more sensitive measure of SES. Our findings are consistent with those from the Midlife Development in the U.S. study, where association between childhood SES and adult obesity were accounted for entirely by adult SES.17
Two studies of African Americans specifically have yielded inconsistent results. In the CARDIA study, there was no association between father or participant education with adult BMI among black women.16
The population differed appreciably from BWHS in that they were younger (aged 18-30) and had lower educational attainment (mean number of years=13.1). In the Pitt County study, parental and adult SES, when modeled together, were inversely associated with adult BMI at baseline among women.8
However, unexpectedly, after 13 years of follow-up, women with higher SES, whether in childhood or adulthood, gained more weight. Like the CARDIA population, the level of adult education in the Pitt County study was much lower than in BWHS, with 30% of women not having graduated from high school.
Most studies did not explicitly assess the mediating role of variables like adult physical activity and diet. The CARDIA16
and Pitt County8
studies adjusted for adult physical activity, smoking, and other factors, but did not compare estimates of effect for the SES measures with and without adjustment. The Monitoring the Future study,9
the National Longitudinal Study of Adolescent Health,14
and the Midlife Development in the U.S. study17
did not account for adult behavioral variables.
Our study contributes the first data on the relation of lifecourse education with adult weight in a large population of African American women. Despite high educational attainment among BWHS participants themselves, an appreciable proportion had parents who did not graduate from high school or college, allowing informative assessment of lifecourse education. We controlled for various potential mediators between education and weight, providing some insight as to mechanism of effect. The correlation between self-reported and technician-measured current weight in BWHS was very high. However, we did not have validation data on weight at age 18, which was self-reported in 1995 when the participants were ages 21-40. In the Nurses’ Health Study II, weight at age 18 reported when participants were age 30-55 was validated by comparison with weight at age 18 recorded on school records.23
The correlation between recalled and recorded weights was 0.87; participants tended to overreport weight at age 18, with a mean difference of 1.4 kg (reported minus recorded weights). While validity of recall may be different among BWHS participants, the correlation between self-report and measured current weight in the BWHS was the same as that found in the Nurse’s Health Study II.24
Parental education in the BWHS was reported in 2009 and represented education achieved by the parent as of 2009. It may not represent parental education during a participant’s childhood if parental education increased after the participant left home. In addition, reporting of parental education may be subject to recall bias. In one small (n=57) study, there was 66% agreement between older adults’ reports of fathers’ occupation during childhood and historical data.25
In a study of over 6000 Scottish men and women, responses during middle age about father’s occupation were compared to occupational class reported during childhood: weighted kappas between the responses were of moderate agreement (0.47 - 0.56).26
Associations of parental SES with two health outcomes associated with parental SES, birth weight and IQ, were weaker based on adult retrospective report than on contemporaneous reports, but were in the expected direction. Furthermore, a review concluded that studies that used contemporaneous reports of childhood SES more consistently reported inverse associations with adult obesity than did studies that used retrospective reporting.2
These observations suggest that any reporting bias in the present study would lead to underestimation of the association.
Another limitation of the present data is that, for some women, weight gain may have preceded achieving the level of education reported in 2003. However, among the 88% of the BWHS population whose education did not increase between 1995 and 2003, the relationships between the participant’s education and the outcomes were similar to those among all women
Education has been shown to be a good indicator of SES among African Americans.27
In addition, it is one of the most widely used measure of SES in the obesity literature since it is easy to obtain and applies to those not in the workforce.28
However, education has a narrower range than other measures, and there are cohort effects.28,29
One review found the most consistent evidence for an inverse association between adult SES and weight came from studies where occupation was the SES measure, followed by education; income was not a consistent predictor of weight.1
Studies of childhood SES have mostly used father’s occupation, particularly those conducted in Europe.2
Most studies that have used parental education have found inverse associations with adult weight among women.7-9,12,13,30
In conclusion, our results suggest that while parental disadvantage, represented by low education, has adverse effects on adult weight, these effects can be largely overcome by high current education, specifically by educational level of college graduate. Having a college degree may result in better understanding of the importance of healthy weight and knowledge of weight control practices, including a healthy diet and adequate exercise. In addition, the increased earnings associated with having a college degree31
may increase access to healthy foods and the ability to maintain physical fitness.