Secular Trends in the Association of Socio-Economic Position with Self-Reported Dietary Attributes and Biomarkers in the US Population: National Health and Nutrition Examination Survey (NHANES) 1971–1975 to NHANES 1999–2002
Objective: Recent reports suggest persistence of health disparities related to socioeconomic position (SEP). To understand if diet may be a contributor to these trends, we examined secular trends in the association of diet and indicators of SEP from 1971–1975 to 1999–2002.
Design: We used data from the National Health and Nutrition Examination Surveys (NHANES) I (1971–1975), II (1976–1980), III (1988–1994) and 1999–2002 to examine the independent associations of poverty income ratio (PIR) and education with diet and biomarkers of diet and disease in 25–74-year-olds (n ¼ 36 600). We used logistic and linear regression methods to adjust for multiple covariates and survey design to examine these associations.
Results: A large PIR differential in the likelihood of reporting a fruit or all five food groups and vitamin C intake, and an education differential in likelihood of obesity and carbohydrate intake, was noted in 1971–1975 but narrowed in 1999–2002 (P , 0.007). The positive association of education with intake of a fruit, vegetable or all five food groups, vitamins A and C, calcium and potassium intake remained unchanged across surveys (P , 0.001). Similarly, the positive association of PIR with the amount of foods and intakes of energy and potassium remained unchanged over three decades (P , 0.001). The education and the PIR differential in energy density, and the PIR differential in the likelihood of obesity, persisted over the period of the four surveys (P , 0.001).
Conclusions: Persistence of unfavourable dietary and biomarker profiles in Americans with low income and education suggests continued need for improvement in the quality of diets of these high-risk groups.