Managing Outliers in Adolescent Food Frequency Questionnaire Data

A Dietary Pattern With More Fruits and Vegetables in Children of Mothers Who Immigrated to the United States From Latin America Is Associated With Healthful Nutrient Intake and Weight Status

BACKGROUND

Children from families who immigrated to the United States may consume a lower-quality diet compared with their US-born peers. However, specific features of their dietary patterns, which could be a focus for improving diet quality, are not well-studied.

OBJECTIVE

The aim of this study was to examine dietary patterns that distinguish interpersonal variability in dietary intake and explore the association of dietary patterns with nutrient intake and weight status.

DESIGN

This study was a cross-sectional analysis of baseline data from the Live Well randomized controlled trial collected between 2009 and 2010.

PARTICIPANTS/SETTING

Study participants included 313 children (3-12 years) whose mothers immigrated to the United States from Latin America and resided in Somerville, Massachusetts.

MAIN OUTCOME MEASURES

Dietary patterns (derived using principal component analysis); nutrient intake (derived from dietary data collected using the Block Food Screener); and weight status (categorized using body mass index z score based on measured height and weight).

STATISTICAL ANALYSES PERFORMED

Nutrient intake levels were compared across quartiles for dietary patterns using analysis of covariance. Multivariable logistic or linear regression models were used to determine the associations between dietary pattern scores and odds of overweight or obesity or z scores.

RESULTS

Two dietary patterns emerged: "fruits and vegetables" and "meat and sweets." Highest adherence to the fruits and vegetables pattern was associated with more healthful nutrient intake and lower odds of having overweight or obesity (odds ratio 0.37; 95% CI 0.16 to 0.98), but not body mass index z score (β = -.07; 95% CI -.51 to 0.36) compared with the lowest adherence. Adherence to the meat and sweets pattern was associated with less healthful nutrient intake but not with the odds of experiencing overweight or obesity (odds ratio 0.48; 95% CI 0.16 to 1.46).

CONCLUSIONS

A healthful dietary pattern in children of families who immigrated to the United States from Latin America may include a variety of fruits and vegetables. Longitudinal studies should be conducted to further assess the role of dietary intake patterns on the health of these children.

Evaluating the healthfulness of Asian American young adult dietary behaviors and its association with family structure: Disaggregated results from NHIS 2015

Background: Asian Americans (AA) young adults face a growing non-communicable disease burden linked with poor dietary behaviors. Family plays a significant role in shaping the diet of AA young adults, although little is known on the specific types of family structures most associated with different dietary behaviors. Aim: This analysis explores the changes in dietary behaviors across different AA young adult family structural characteristics. Methods: Nationwide data of 18-35-year-old self-identified Asians surveyed in the 2015 National Health Interview Survey (NHIS) was analyzed. Family structure was measured through family size, family health, and family members in one's life. The Dietary Screener Questionnaire (DSQ) measured the average intake of 10 food and nutrient groups. Published dietary guidelines were used to calculate the number of dietary recommendations met. Results: 670 AA young adults with dietary data were analyzed (26.1% Asian Indian, 26.1% Chinese, 19.3% Filipino, 28.5% other Asian). Participants had an average family size of 2.3. In weighted analyses, 19% of AA young adults met none of the examined dietary recommendations, and only 14% met 3-4 guidelines. Living with a child was associated meeting more dietary recommendations (adjusted odds ratio [AOR]: 1.22; 95%CI: 1.05, 1.42). The adjusted association between living with an older adult and lower odds of meeting dietary recommendations approached significance (AOR: 0.70; 95%CI: 0.49, 1.00). Conclusions: Findings revealed the important role of children and older adults in influencing the diet of AA young adults. Further mixed-methods research to disentangle mechanisms behind the influence of family structure on diet is warranted.

Outliers in nutrient intake data for U.S. adults: national health and nutrition examination survey 2017-2018

Objectives

An important step in preparing data for statistical analysis is outlier detection and removal, yet no gold standard exists in current literature. The objective of this study is to identify the ideal decision test using the National Health and Nutrition Examination Survey (NHANES) 2017-2018 dietary data.

Methods

We conducted a secondary analysis of NHANES 24-h dietary recalls, considering the survey's multi-stage cluster design. Six outlier detection and removal strategies were assessed by evaluating the decision tests' impact on the Pearson's correlation coefficient among macronutrients. Furthermore, we assessed changes in the effect size estimates based on pre-defined sample sizes. The data were collected as part of the 2017-2018 24-h dietary recall among adult participants (N=4,893).

Results

Effect estimate changes for macronutrients varied from 6.5 % for protein to 39.3 % for alcohol across all decision tests. The largest proportion of outliers removed was 4.0 % in the large sample size, for the decision test, >2 standard deviations from the mean. The smallest sample size, particularly for alcohol analysis, was most affected by the six decision tests when compared to no decision test.

Conclusions

This study, the first to use 2017-2018 NHANES dietary data for outlier evaluation, emphasizes the importance of selecting an appropriate decision test considering factors such as statistical power, sample size, normality assumptions, the proportion of data removed, effect estimate changes, and the consistency of estimates across sample sizes. We recommend the use of non-parametric tests for non-normally distributed variables of interest.