Diet Data Collected Using 48-h Dietary Recall: Within-and Between-Person Variation.

Background and Aims: Forty-eight-hour dietary recall is a valuable source of information regarding food consumption in a population-based sample. This method covers 2 consecutive days in a single interview. Nevertheless, the number of assessments and the sample size necessary to estimate usual intake are unknown. We aimed to assess sources of variation, sample sizes, and numbers of days necessary to estimate usual nutrient intake using the 48-h dietary recall. Methods: This was a population-based cross-sectional study including 237 participants, 11-90 years old, selected using multistage probabilistic sampling to obtain data using 48-h dietary recall. Analysis of variance was used to calculate within- and between-person variation and determine the statistical parameters necessary to calculate sample size and the number of days required to calculate the usual energy and nutrient intake. Results: Within-person variation was generally lower than between-person variation, except for calcium ( CV w 2 = 40.8; CV b 2 = 38.4%), magnesium ( CV w 2 = 27.4; CV b 2 = 18.7%), and monounsaturated fat ( CV w 2 = 20.0; CV b 2 = 17.3%) for the entire group and magnesium for women ( CV w 2 = 28.3; CV b 2 = 91.8%). The number of days and sample size required to determine usual energy and nutrient intake varied substantially with gender and age (e.g., vitamin C in women N = 9, in men N = 1,641). Conclusions: Energy and nutrient intake assessment using the 48-h dietary recall misrepresents within-person variation but can generate acceptable results for between-person variation. The calculation of sample size and number of days required to determine usual energy and nutrient intake might have been affected by inadequate assessment of the within-person variation.

Associations between cardiorespiratory fitness, physical activity, intraindividual variability in behavior, and cingulate cortex in younger adults.

BACKGROUND: Higher levels of cardiorespiratory fitness (CRF) and greater amounts of physical activity have been associated with lower intraindividual variability (IIV) in executive function in children and older adults. In the present study, we examined whether CRF, measured as maximal oxygen uptake (VO2max), and daily volume of moderate-to-vigorous intensity physical activity (MVPA) were associated with IIV of reaction time during performance of the incongruent condition of the Stroop task in younger adults. Further, we examined whether the thickness of the cingulate cortex was associated with regulating variability in reaction time performance in the context of CRF or physical activity. METHODS: CRF (measured as VO2max), accelerometry-measured MVPA, Stroop performance, and thickness of the rostral anterior cingulate cortex (rACC) derived from magnetic resonance imaging data were collected in 48 younger adults (age = 24.58 ± 4.95 years, mean ± SD). Multiple regression was used to test associations between IIV during the Stroop task and CRF, MVPA, and rACC thickness. Mediation was tested using maximum likelihood estimation with bootstrapping. RESULTS: Consistent with our predictions, higher VO2max was associated with greater rACC thickness for the right hemisphere and greater daily amounts of MVPA were associated with greater rACC thickness for both the left and right hemispheres. Greater thickness of the right rACC was associated with lower IIV for the incongruent condition of the Stroop task. CRF and MVPA were not directly associated with IIV. However, we did find that IIV and both CRF and MVPA were indirectly associated via the thickness of the right rACC. CONCLUSION: These results indicate that higher CRF and greater daily volume of MVPA may be associated with lower IIV during the Stroop task via structural integrity of the rACC. Randomized controlled trials of MVPA would provide crucial information about the causal relations between these variables.

Performance of statistical methods to correct food intake distribution: comparison between observed and estimated usual intake.

There are statistical methods that remove the within-person random error and estimate the usual intake when there is a second 24-h recall (24HR) for at least a subsample of the study population. We aimed to compare the distribution of usual food intake estimated by statistical models with the distribution of observed usual intake. A total of 302 individuals from Rio de Janeiro (Brazil) answered twenty, non-consecutive 24HR; the average length of follow-up was 3 months. The usual food intake was considered as the average of the 20 collection days of food intake. Using data sets with a pair of 2 collection days, usual percentiles of intake of the selected foods using two methods were estimated (National Cancer Institute (NCI) method and Multiple Source Method (MSM)). These estimates were compared with the percentiles of the observed usual intake. Selected foods comprised a range of parameter distributions: skewness, percentage of zero intakes and within- and between-person intakes. Both methods performed well but failed in some situations. In most cases, NCI and MSM produced similar percentiles between each other and values very close to the true intake, and they better represented the usual intake compared with 2-d mean. The smallest precision was observed in the upper tail of the distribution. In spite of the underestimation and overestimation of percentiles of intake, from a public health standpoint, these biases appear not to be of major concern.

Within-person coupling of changes in cortisol, testosterone, and DHEA across the day in adolescents.

We comprehensively examined within-person and between-person associations between cortisol and DHEA and cortisol and testosterone across the day. Data are from a sample of 213 adolescents aged 11-16 (M = 13.7, SD = 1.5 years) from the Northeastern US who were oversampled for psychopathology symptoms. Six repeated measures of hormone levels across 3 days were used to test three specific questions of cortisol-DHEA and cortisol-testosterone associations within individuals (coupling) across the day, and one question of cortisol-DHEA and cortisol-testosterone diurnal slopes were associated between adolescents. Results consistently revealed positive cortisol-DHEA and cortisol-testosterone coupling across the day, often more pronounced in girls relative to boys. Cortisol and DHEA slopes were positively associated, whereas cortisol and testosterone were negatively associated between-adolescents. Findings suggest multiple mechanisms and highlight the multifaceted nature of associations of hormone changes during adolescence and importance of considering both axes for between- and within-person aspects of neuroendocrine development.

Children's nutrient intake variability is affected by age and body weight status according to results from a Brazilian multicenter study.

A major challenge in nutritional studies focusing on children is estimating "true" intake because the type and amount of foods eaten change throughout growth and development, thereby affecting the variability of intake. The present study investigated the hypothesis that age and body weight status affect the ratio of the within- and between-subject variation of intakes (VR) as well as the number of days of dietary assessment (D) of energy and nutrients. A total of 2,981 Brazilian preschoolers aged 1-6 years were evaluated in a cross-sectional study. Weighed food records and estimated food records were used to assess dietary intake inside and outside of school. Within- and between-subject variations of intakes were estimated by multilevel regression models. VR and D were calculated according to age group and body weight status. VR ranged from 1.17 (calcium) to 8.70 (fat) in the 1- to 2-year-old group, and from 1.47 (calcium) to 8.95 (fat) in the 3- to 6-year-old group. Fat, fiber, riboflavin, folate, calcium, phosphorus, and iron exhibited greater VR and D in the 3- to 6-year-old group. For energy, carbohydrates, and protein, both within- and between-subject variation increased with increasing age. In both body weight groups, calcium showed the lowest VR. Fat showed the highest VR in nonoverweight/obese children (9.47), and fiber showed the highest VR in overweight/obese children (8.74). For most nutrients, D = 7 was sufficient to correctly rank preschoolers into tertiles of intake. In conclusion, age and body weight status affected the within- and between-subject variation and the VR of energy and nutrient intakes among Brazilian preschool children.

Variância intrapessoal para ajuste da distribuição de nutrientes em estudos epidemiológicos / Within-person variance for adjusting nutrient distribution in epidemiological studies / Varianza intrapersonal para ajuste de la distribución de nutrientes en estudios epidemiológicos

O objetivo do estudo foi apresentar a fração da variância intrapessoal para ajuste da distribuição de nutrientes de adultos e idosos. Utilizaram-se dados de inquérito populacional com amostra representativa (n = 511) de indivíduos com 19 anos ou mais do município de São Paulo, SP, em 2007. A fração da variância intrapessoal foi obtida pelo método proposto pela Iowa State University. Observaram-se diferenças nas frações das variâncias intrapessoais de nutrientes segundo sexo. Esses valores devem ser utilizados para ajustar a distribuição da ingestão de nutrientes, pois sua não utilização pode resultar em viés na análise e interpretação de dados.

The objective of the study was to present the within-person variance component for adjusting nutrient distribution in adults and elderly people. The data used were from a population-based survey with a representative sample (n = 511) of individuals aged 19 years and over in the municipality of São Paulo, Southeastern Brazil, conducted in 2007. The within-person variance component was obtained using the Iowa State University method. Differences in within-person variance components were observed for some nutrients according to gender. These values should be used to adjust nutrient intake distributions, because lack of adjustment may result in biased data analysis and interpretation.

El objetivo del estudio fue presentar la fracción de la varianza intrapersonal para juste de la distribución de nutrientes de adultos y ancianos. Se utilizaron datos de pesquisa poblacional con muestra representativa de 511 individuos con 19 años o más del municipio de Sao Paulo, Sureste de Brasil, en 2007. La fracción de la varianza intrapersonal fue obtenida por el método propuesto por el Iowa State University. Se observaron diferencias en las fracciones de las varianzas intrapersonales de nutrientes según género. Estos valores deben ser utilizados para ajustar la distribución de la ingestión de nutrientes, ya que la no utilización puede resultar en sesgo en el análisis e interpretación de datos.

Within- and between-person variations as determinant factors to calculate the number of observations to estimate usual dietary intake of adolescents / Variação intra e interpessoal como fatores determinantes para o cálculo do número de observações para estimar a ingestão dietética habitual de adolescentes

This cross-sectional study describes the variation in the dietary intake of energy and macronutrients based on estimated coefficients of within- and between-person variation and intends to calculate the number of days required to evaluate the dietary intake of adolescents in Piracicaba, Brazil. The sample was made up by ninety-two adolescents aged between eleven and sixteen years. Interviews were performed to assess demographic, anthropometric and dietary variables, which were evaluated by the answers obtained through two 24-hour recalls. Descriptive analyses were performed and variances and Coefficients of variation within- and between-person were obtained by results of one-way ANOVA. The mean energy intake observed was 2,326.2 kilocalories; mean macronutrient intake came to 89.0 grams of fatty acids, 305.3 grams of carbohydrates and 82.2 grams of proteins. Coefficients of within-person variation ranged from 36 percent to 45 percent, while between-person coefficients varied from 26 percent to 31 percent. Variance ratios ranged from 1.35 (carbohydrate) to 2.62 (protein). The lowest number of observations required to correctly evaluate the usual diet calculated (r = 0.90) was six days, for carbohydrates while the highest was eleven, for proteins. Coefficients of variation were similar to those observed in international studies. We conclude that, in this study, two observations were sufficient to obtain reasonable correlations. However, six evaluations are necessary for these adolescents in order to obtain excellent correlations.

Este estudo transversal descreve a variabilidade do consumo alimentar de energia e macronutrientes a partir da estimativa dos coeficientes de variação intra e interpessoal e calcula o número de dias necessários para se avaliar a ingestão dietética de adolescentes de Piracicaba, Brasil. A amostra foi constituída por 92 adolescentes com idade entre 11 e 16 anos. Por meio de entrevistas, foram avaliadas variáveis demográficas, antropométricas e de ingestão dietética, levantada por meio de dois Recordatórios de 24h. Foram realizadas análises descritivas, sendo que as variâncias e os coeficientes de variação intra e interpessoal foram obtidos a partir dos resultados da ANOVA com um fator de classificação. O consumo médio de energia observado foi de 2.326,2 Kcal, e em relação aos macronutrientes foram observados valores de 89,0g de lipídios, 305,3g de carboidratos e 82,2g de proteínas. Os coeficientes de variação intrapessoal variaram de 36 por cento a 45 por cento enquanto os coeficientes de variação interpessoal variaram de 26 por cento a 31 por cento. A razão entre as variâncias variou de 1,35 (carboidrato) a 2,62 (proteína). O menor número de observações necessárias para avaliar corretamente (r = 0,90) a dieta habitual foi de 6 dias para carboidratos. O maior número foi para proteínas (11 dias). Os coeficientes de variação foram semelhantes aos observados em estudos internacionais. Conclui-se que, para o presente estudo, duas observações foram suficientes para a obtenção de coeficientes de correlação razoáveis. No entanto, para se obter ótimos coeficientes de correlação, são necessárias no mínimo seis avaliações destes adolescentes.