Is it necessary to transform nutrient variables prior to statistical analyses?

Dietary associations of household food insecurity among children of Mexican descent: results of a binational study

BACKGROUND/OBJECTIVE

Children of Mexican descent frequently experience household food insecurity both in the United States and Mexico. However, little is known about the associations of food insecurity with dietary intake. This study aimed to understand the level of perceived food insecurity and its association with dietary intake among children of Mexican descent residing in the United States and Mexico.

DESIGN

This cross-sectional study utilized data from a 2006 binational study of 5-year-old children of Mexican descent living in migrant communities in California and Mexico.

METHODS

In California, children were 301 participants from the Center for the Health Assessment of Mothers and Children of Salinas study, a longitudinal birth cohort in a Mexican immigrant community. Mexican children (n=301) were participants in the Proyecto Mariposa study, which was designed to capture a sample of women and their children living in Mexico who closely resembled the California sample, yet who never migrated to the United States. Household food insecurity was measured using the US Department of Agriculture Food Security Scale and dietary intake was assessed with food frequency questionnaires. Analysis of variance was used to examine unadjusted and adjusted differences in total energy, nutrient intake, and consumption of food groups by household food security status.

RESULTS

Approximately 39% of California mothers and 75% of Mexico mothers reported low or very low food security in the past 12 months (P<0.01). Children in the United States experiencing food insecurity consumed more fat, saturated fat, sweets, and fried snacks than children not experiencing food insecurity. In contrast, in Mexico food insecurity was associated with lower intake of total carbohydrates, dairy, and vitamin B-6.

CONCLUSIONS

Programs and policies addressing food insecurity in the United States and Mexico may need to take steps to address dietary intake among children in households experiencing food insecurity, possibly through education and programs to increase resources to obtain healthful foods.

Nutrient intakes and food consumption patterns among Ontario students in grades six, seven, and eight

BACKGROUND

The increased prevalence of overweight in Canadian children has stimulated interest in their lifestyle behaviours. The purpose of this research was to investigate dietary intake and food behaviours of Ontario students in grades six, seven, and eight.

METHODS

Males and females from grades six to eight were recruited from a stratified random selection of schools from Ontario. Data were collected using the web-based "Food Behaviour Questionnaire", which included a 24-hour diet recall and food frequency questionnaire. Nutrients were analyzed using ESHA Food Processor and the 2001 Canadian Nutrient File database. Body Mass Index (BMI) was calculated based on self-reported weight and height, and classified according to the Centers for Disease Control BMI for age percentiles.

RESULTS

The sample included males (n = 315) and females (n = 346) in grades 6, 7, and 8 from 15 schools in Ontario. According to Canada's Food Guide to Healthy Eating (CFGHE), median intakes were below recommendations for all participants, with the exception of meat and alternatives. Participants consumed a median of 54%, 15%, 31%, 11%, and 8% of total energy from carbohydrates, protein, total fat, saturated fat, and added sugars, respectively. Participants consumed 25% of total energy from foods from the "other" food group (CFGHE). Males had higher intakes of energy, carbohydrates, fat, saturated fat, monounsaturated fat, protein, thiamine, niacin, iron, and zinc than females (all p < 0.05), and consumed more grain products servings (p < 0.05).

CONCLUSION

The high consumption of "other" foods, at the expense of nutrient-dense food groups, may ultimately be contributing to the increased weights in childhood and adolescence.

The Role of Noradrenergic and Dopaminergic Hyperactivity in the Development of Spontaneous Recurrence of Methamphetamine Psychosis and Susceptibility to Episode Recurrence

The role of dopaminergic activity in susceptibility of methamphetamine (MAP) psychosis (flashbacks) to subsequent spontaneous recurrences was studied. Plasma monoamine metabolite levels were assayed in 23 flashbackers, of whom 10 experienced a single flashback, 8 exhibited subsequent flashbacks and 5 with the last episode; 18 nonflashbackers with a history of MAP psychosis; 9 subjects with persistent MAP psychosis; and 19 MAP user and 10 nonuser controls. All flashbackers had undergone frightening stressful experiences during previous MAP use. Their flashbacks were triggered by mild psychosocial stressors. Plasma norepinephrine (NE) levels increased with the increase in plasma levels of 3-methoxytyramine (3-MT), an index of dopamine release, during flashbacks in the 23 flashbackers. Of these, the 8 with subsequent episodes had markedly increased NE levels and increased 3-methoxytyramine levels during flashbacks. However, the 5 flashbackers with the last episode had moderately increased NE levels, and the 10 with a single episode displayed small increases in NE levels during flashbacks. Their 3-MT levels did not significantly differ from the levels in the control groups. Thus, increased DA release in addition to robust noradrenergic hyperactivity in response to mild psychosocial stressors may be important in susceptibility to subsequent flashbacks.

Factors for susceptibility to episode recurrence in spontaneous recurrence of methamphetamine psychosis

The relation between increased sensitivity to stress associated with noradrenergic hyperactivity and dopaminergic changes, and susceptibility to subsequent spontaneous recurrences of methamphetamine (MAP) psychosis (flashbacks) was examined. Plasma monoamine metabolite levels were assayed in 19 flashbackers, of whom 10 experienced a single flashback and 9 exhibited subsequent flashbacks, 18 nonflashbackers with a history of MAP psychosis, 9 subjects with persistent MAP psychosis, and 22 MAP user and 10 nonuser controls. All flashbackers had undergone frightening stressful experiences during previous MAP use. They exhibited flashbacks in response to mild psychosocial stressors. There was no significant difference in the number of stressful experiences and having mild psychosocial stressors between the two flashbacker subgroups. Plasma norepinephrine (NE) levels increased with a small increase in plasma levels of 3-methoxytyramine (3-MT), an index of dopamine release, during flashbacks in the 19 flashbackers. Of the 19 flashbackers, the 9 with subsequent episodes had markedly increased NE levels and slightly increased 3-MT levels during flashbacks, while the 10 with a single episode displayed small increases in NE and 3-MT levels during flashbacks. The 9 flashbackers with subsequent episodes had a longer duration of imprisonment than the 10 flashbackers with a single episode. Thus, robust noradrenergic hyperactivity with slightly increased DA release in response to mild stress may predict subsequent flashbacks. Long-term exposure to distressing situations appears to contribute to susceptibility to subsequent flashbacks.

Susceptibility to subsequent episodes of spontaneous recurrence of methamphetamine psychosis

We examine susceptibility to subsequent spontaneous recurrences of methamphetamine psychosis (i.e. flashbacks) in 11 flashbackers with a single episode and in nine flashbackers with subsequent episodes. All had undergone frightening stressful experiences during previous MAP use. Mild psychosocial stressors then triggered flashbacks. During flashbacks, the nine flashbackers with subsequent episodes had more markedly increased norepinephrine levels, with slightly increased 3-methoxytyramine levels. The duration of imprisonment in this subgroup approached significantly long levels than in the 11 flashbackers with a single episode. Robust noradrenergic hyperactivity with slightly increased dopamine release may therefore predict subsequent flashbacks. Longer exposure to distressing situations may also contribute to robust noradrenergic hyperactivity.

Long-stay patients in the pediatric intensive care unit

OBJECTIVE

Length of stay in the pediatric intensive care unit (PICU) is a reflection of patient severity of illness and health status, as well as PICU quality and performance. We determined the clinical profiles and relative resource use of long-stay patients (LSPs) and developed a prediction model to identify LSPs for early quality and cost saving interventions.

DESIGN

Nonconcurrent cohort study.

SETTING

A total of 16 randomly selected PICUs and 16 volunteer PICUs.

PATIENTS

A total of 11,165 consecutive admissions to the 32 PICUs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

LSPs were defined as patients having a length of stay greater than the 95th percentile (>12 days). Logistic regression analysis was used to determine which clinical characteristics, available within the first 24 hrs after admission, were associated with LSPs and to create a predictive algorithm. Overall, LSPs were 4.7% of the population but represented 36.1% of the days of care. Multivariate analysis indicated that the following factors are predictive of long stays: age <12 months, previous ICU admission, emergency admission, no CPR before admission, admission from another ICU or intermediate care unit, chronic care requirements (total parenteral nutrition and tracheostomy), specific diagnoses including acquired cardiac disease, pneumonia, and other respiratory disorders, having never been discharged from the hospital, need for ventilatory support or an intracranial catheter, and a Pediatric Risk of Mortality III score between 10 and 33. The performance of the prediction algorithm in both the training and validation samples for identifying LSPs was good for both discrimination (area under the receiver operating characteristics curve of 0.83 and 0.85, respectively), and calibration (goodness of fit, p = .33 and p = .16, respectively). LSPs comprised from 2.1% to 8.1% of individual ICU patients and occupied from 15.2% to 57.8% of individual ICU bed days.

CONCLUSIONS

LSPs have less favorable outcomes and use more resources than non-LSPs. The clinical profile of LSPs includes those who are younger and those that require chronic care devices. A predictive algorithm could help identify patients at high risk of prolonged stays appropriate for specific interventions.

Susceptibility to subsequent episodes in spontaneous recurrence of methamphetamine psychosis

The relation is examined between increased sensitivity to stress associated with noradrenergic hyperactivity and dopaminergic changes, and susceptibility to subsequent spontaneous recurrences of methamphetamine (MAP) psychosis (i.e., flashbacks). Plasma monoamine metabolite levels were assayed in 23 flashbackers, 19 nonflashbackers with a history of MAP psychosis, 10 subjects with persistent MAP psychosis, and 21 MAP user and 9 nonuser controls. All 23 flashbackers had undergone frightening stressful experiences during previous MAP use. Mild psychosocial stressors then triggered flashbacks. The 12 flashbackers with further episodes had markedly increased norepinephrine levels and slightly increased plasma levels of 3-methoxytyramine, an index of dopamine release. While the 11 flashbackers with a single episode displayed small increases in norepinephrine and 3-methoxytyramine levels. Thus, robust noradrenergic hyperreactivity, involving increased dopamine release in response to mild stress may predispose to further episodes of flashbacks.

Increased sensitivity to stress in spontaneous recurrence of methamphetamine psychosis: noradrenergic hyperactivity with contribution from dopaminergic hyperactivity

The significance of increased sensitivity to stress associated with noradrenergic hyperactivity involving dopaminergic change in spontaneous recurrences of methamphetamine (MAP) psychosis (flashbacks) was examined. Plasma monoamine metabolite levels were assayed in 18 subjects with flashbacks who had been exposed to stressful events plus MAP-induced frightening psychotic symptoms (N = 11) or frightening psychotic symptoms alone (N = 7) during previous MAP use, in 15 nonflashbackers with a history of MAP psychosis, in 8 subjects with persistent MAP psychosis, and in 27 control subjects. Monoaminergic values were subjected to a square-root transformation, rendering the distribution normal. The numbers of stressful events (mostly threatening events) and frightening psychotic symptoms were significantly higher in the flashbackers than in the nonflashbackers. Factors triggering flashbacks were mild psychosocial stressors (mostly a mild fear of other people). During flashbacks, plasma norepinephrine levels increased, and the flashbackers, 11 of whom had experienced stressful events plus frightening psychotic symptoms, had an additional small increase in plasma levels of 3-methoxytyramine, which is indicative of dopamine release. Thus, threatening stressful events, together with MAP use, may induce noradrenergic hyperreactivity to subsequent mild stressors. Threatening, stressful events plus frightening psychotic symptoms may further induce increased dopamine release in response to mild stressors. Increased sensitivity to stress associated with noradrenergic hyperactivity involving increased dopamine release may have elicited memories of MAP psychosis related to frightening, stressful experiences. The increased sensitivity may be critical for the development of flashbacks.

Stress induced spontaneous recurrence of methamphetamine psychosis: the relation between stressful experiences and sensitivity to stress

We examined increased sensitivity to stress in relation to spontaneous recurrences of methamphetamine (MAP) psychosis (i.e., flashbacks). Plasma monoamine metabolite levels were assayed in: 26 flashbackers, of whom 11 were on neuroleptics before and during the study, and the other 15 received neuroleptics in the course of the study; 18 non-flashbackers with a history of MAP psychosis; eight subjects with persistent MAP psychosis; and 23 MAP user and 11 non-user controls. The 26 flashbackers had experienced stressful events and/or MAP-induced fear-related psychotic symptoms during previous MAP use. Mild psychosocial stressors then triggered flashbacks. During flashbacks plasma norepinephrine levels increased markedly; among the flashbackers, those with a history of stressful events, whether or not they had experienced fear-related symptoms, showed a further increase in 3-methoxytyramine levels. Stressful experiences, together with MAP use, may therefore induce sensitization to stress associated with noradrenergic hyperactivity, involving increased dopamine release, and so triggering flashbacks.

Factors affecting the development of spontaneous recurrence of methamphetamine psychosis

The process triggering spontaneous recurrences of methamphetamine (MAP) psychosis (i.e. flashbacks) was studied in 41 flashbackers, along with 84 non-flashbackers with a history of MAP psychosis. Plasma monoamine metabolite levels were assayed in 25 of the 41 flashbackers, 16 of the 84 non-flashbackers, 9 subjects with persistent MAP psychosis and 28 control subjects. All flashbackers had experienced threatening events or frightening paranoid-hallucinatory states during previous MAP use. The dominant factor triggering flashbacks was a mild fear of other people. Plasma norepinephrine levels were elevated during flashbacks. The results suggest that a mild fear of other people may have elicited memories of MAP psychosis associated with threatening experiences through increased sensitivity to psychosocial stressors. As a result the flashbacks occurred, including an increase in peripheral noradrenergic activity.

Analyzing intensive care unit length of stay data: problems and possible solutions

OBJECTIVES

To explore methods of evaluating the length of stay patterns of intensive care unit (ICU) patients. It was hypothesized that the mean does not adequately describe the typical length of stay (central tendency) because distribution patterns are often markedly skewed by patients with extended stays. Therefore, other descriptors are needed. In addition, ways are needed to identify outliers-patients with stays longer or shorter than the bulk of the data.

DESIGN

Review of retrospective data.

SETTING

University hospital surgical ICU.

PATIENTS

Representative data included all (4,499) patients admitted over a 6-yr period. Each was assigned to a diagnostic group that represented either a frequently performed surgical procedure (e.g., thymectomy) or in cases where there was no predominant procedure, a surgical discipline (e.g., otolaryngology).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The frequency distributions were usually skewed to the right and included two populations of interest: The portion with the majority of observations ("body"), which described "typical" behavior, and the "tail", which provided information on outliers. The average of the mean lengths of stay of all diagnostic groups was higher than the average of the medians (3.9 +/- 1.8 [SD] vs. 2.7 +/- 1.1 days, p < .001) and modes (2.1 +/- 1.2 days, p < .001), reflecting the rightward skewness of the length of stay frequency distributions. The median +/- 1 day included 75 +/- 13% of the patients, thus confirming that the median was the most useful descriptor of central tendency. Various methods were used to identify outliers. Histograms of the frequency distributions were examined and outliers visually identified. Conventional outlier analysis labeled as outliers patients staying greater than two standard deviations from the mean stay. This method underestimated the number of outliers when the distributions were skewed to the right. Another method involved designating a specific length of stay (e.g., 7 or 10 days) or percentage of patients as the outlier threshold. Each method designated different numbers of patients as outliers.

CONCLUSIONS

When analyzing length of stay data it is important to visually examine the frequency distribution because it is often skewed to the right. This skewness renders traditional parameters such as the mean and standard deviation less useful for describing the typical length of stay. Instead, the median, mode, and harmonic mean should be used. When reporting length of stay, some indication of the characteristics of the data should be presented. A graph of the frequency distribution rapidly allows the reader to determine its shape. A simple method is to report the mean, median, and range.