Difference in diet quality trends between children and adults in the United States: A serial cross-sectional study from 1999 to 2018

Background and Objectives: Previous studies had shown that trends in diet quality between children and adults may vary but lack quantitative comparisons. We aimed to compare diet quality and its trends between US children and adults in this research. Methods and Study Design: Children aged 2 to 18 and adults aged 19 to 59 years old in the US were enrolled the serial cross-sectional analysis of National Health and Nutrition Examination Survey (NHANES) cycles from 1999 to 2018. Diet quality was assessed using the Healthy Eating Index-2015 (HEI-2015), and trends were analyzed by joinpoint regression model. Results: This study included 31988 children and 34317 adults. From 1999 to 2018, there was a trend-change among 5 children's components trends (including total fruits in 2011-2012, whole fruits in 2005-2006, greens and beans in 2013-2014, dairy in 2013-2014, and total protein foods in 2013-2014, p for joinpoint <0.05 for each) and overall trend in 2013-2014, whereas no significant trend-change in adults' trend. The trends of overall HEI-2015 between children (average annual percent change 0.3%; 95% CI: -0.1% to 0.8%) and adults (0.3%; 95%CI: 0.0% to 0.6%) showed no significant difference in parallelism (p for parallelism=0.60), but a significant difference in coincidence (intercept -7.7 +/- 3.7 among children; -2.3 +/- 2.5 among adults; p for coincidence <0.05). Conclusions: Children had a different trend with more trend-changes in diet quality compared with adults, and the diet quality of children was worse than that of adults during 1999-2018 in the US.