Elena N. Naumova

A Community Intervention Reduces BMI z-score in Children: Shape Up Somerville First Year Results

Objective: The objective was to test the hypothesis that a community‐based environmental change intervention could prevent weight gain in young children (7.6 ± 1.0 years).

Influenza Seasonality: Underlying Causes and Modeling Theories

Influenza (or “flu”) leads to the hospitalization of more than 200,000 people yearly and results in 36,000 deaths from flu or flu-related complications in the United States ([15][1]), striking both the elderly and infant populations particularly hard ([24][2]). Two members of the

Adolescent obesity and risk for subsequent major depressive disorder and anxiety disorder: prospective evidence.

Objective: To assess whether adolescent obesity is associated with risk for development of major depressive disorder (MDD) or anxiety disorder. Obesity has been linked to psychosocial difficulties among youth. Methods: Analysis of a prospective community-based cohort originally from upstate New York, assessed four times over 20 years. Participants (n = 776) were 9 to 18 years old in 1983; subsequent assessments took place in 1985 to 1986 (n = 775), 1991 to 1994 (n = 776), and 2001 to 2003 (n = 661). Using Cox proportional hazards analysis, we evaluated the association of adolescent (age range, 12–17.99 years) weight status with risk for subsequent MDD or anxiety disorder (assessed at each wave by structured diagnostic interviews) in males and females. A total of 701 participants were not missing data on adolescent weight status and had ≥1 subsequent assessments. MDD and anxiety disorder analyses included 674 and 559 participants (free of current or previous MDD or anxiety disorder), respectively. Adolescent obesity was defined as body mass index above the age- and gender-specific 95th percentile of the Centers for Disease Control and Prevention growth reference. Results: Adolescent obesity in females predicted an increased risk for subsequent MDD (adjusted hazard ratio (HR) = 3.9; 95% confidence interval (CI) = 1.3, 11.8) and for anxiety disorder (HR = 3.8; CI = 1.3, 11.3). Adolescent obesity in males was not statistically significantly associated with risk for MDD (HR = 1.5; CI = 0.5, 3.5) or anxiety disorder (HR = 0.7; CI = 0.2, 2.9). Conclusion: Females obese as adolescents may be at increased risk for development of depression or anxiety disorders. BMI = body mass index; CDC = Centers for Disease Control and Prevention; CI = confidence interval; CIC = Children in the Community Study; DSM = Diagnostic and Statistical Manual of Mental Disorders; DISC = Diagnostic Interview Schedule for Children; HR = hazard ratio; SCID-IV = Structured Clinical Interview for DSM-IV Disorders; SD = standard deviation; SES = socioeconomic status.

Ambient air pollution and hospitalization for congestive heart failure among elderly people in seven large US cities.

OBJECTIVES Preexisting data sets were used to investigate the association between hospital admissions for congestive heart failure and air pollutants. METHODS Medicare hospital admissions data, ambient air pollution monitoring data, and meteorological data were used to create daily values of hospital admissions for congestive heart failure, maximum hourly temperature, and maximum hourly levels of carbon monoxide, nitrogen dioxide, sulfur dioxide, and ozone. Data were compiled for each of seven cities (Chicago, Detroit, Houston, Los Angeles, Milwaukee, New York, and Philadelphia) for 1986 through 1989. Single-pollutant and multipollutant models with adjustments for temperature, seasonal effects, and weekly cycles were used in conducting negative binomial regression analyses. RESULTS Ambient carbon monoxide levels were positively associated with hospital admissions for congestive heart failure in the single-pollutant and multipollutant models for each of the seven cities. The relative risk of hospital admission for congestive heart failure associated with an increase of 10 ppm in carbon monoxide ranged from 1.10 in New York to 1.37 in Los Angeles. CONCLUSIONS Hospital admissions for congestive heart failure exhibited a consistent association with daily variations in ambient carbon monoxide. This association was independent of season, temperature, and other major gaseous pollutants.

Seasonality in six enterically transmitted diseases and ambient temperature

We propose an analytical and conceptual framework for a systematic and comprehensive assessment of disease seasonality to detect changes and to quantify and compare temporal patterns. To demonstrate the proposed technique, we examined seasonal patterns of six enterically transmitted reportable diseases (EDs) in Massachusetts collected over a 10-year period (1992-2001). We quantified the timing and intensity of seasonal peaks of ED incidence and examined the synchronization in timing of these peaks with respect to ambient temperature. All EDs, except hepatitis A, exhibited well-defined seasonal patterns which clustered into two groups. The peak in daily incidence of Campylobacter and Salmonella closely followed the peak in ambient temperature with the lag of 2-14 days. Cryptosporidium, Shigella, and Giardia exhibited significant delays relative to the peak in temperature (approximately 40 days, P<0.02). The proposed approach provides a detailed quantification of seasonality that enabled us to detect significant differences in the seasonal peaks of enteric infections which would have been lost in an analysis using monthly or weekly cumulative information. This highly relevant to disease surveillance approach can be used to generate and test hypotheses related to disease seasonality and potential routes of transmission with respect to environmental factors.

Analysis of human immune responses in quasi-experimental settings: tutorial in biostatistics.

BackgroundHuman immunology is a growing field of research in which experimental, clinical, and analytical methods of many life science disciplines are utilized. Classic epidemiological study designs, including observational longitudinal birth cohort studies, offer strong potential for gaining new knowledge and insights into immune response to pathogens in humans. However, rigorous discussion of methodological issues related to designs and statistical analysis that are appropriate for longitudinal studies is lacking.MethodsIn this communication we address key questions of quality and validity of traditional and recently developed statistical tools applied to measures of immune responses. For this purpose we use data on humoral immune response (IR) associated with the first cryptosporidial diarrhea in a birth cohort of children residing in an urban slum in south India. The main objective is to detect the difference and derive inferences for a change in IR measured at two time points, before (pre) and after (post) an event of interest. We illustrate the use and interpretation of analytical and data visualization techniques including generalized linear and additive models, data-driven smoothing, and combinations of box-, scatter-, and needle-plots.ResultsWe provide step-by-step instructions for conducting a thorough and relatively simple analytical investigation, describe the challenges and pitfalls, and offer practical solutions for comprehensive examination of data. We illustrate how the assumption of time irrelevance can be handled in a study with a pre-post design. We demonstrate how one can study the dynamics of IR in humans by considering the timing of response following an event of interest and seasonal fluctuation of exposure by proper alignment of time of measurements. This alignment of calendar time of measurements and a childs age at the event of interest allows us to explore interactions between IR, seasonal exposures and age at first infection.ConclusionsThe use of traditional statistical techniques to analyze immunological data derived from observational human studies can result in loss of important information. Detailed analysis using well-tailored techniques allows the depiction of new features of immune response to a pathogen in longitudinal studies in humans. The proposed staged approach has prominent implications for future study designs and analyses.

Dairy food consumption and body weight and fatness studied longitudinally over the adolescent period

OBJECTIVE: Although research suggests that adolescents, particularly girls, may avoid dairy products due to concerns that these foods are ‘fattening,’ the longitudinal relation between consumption of dairy foods and relative weight status during adolescence has not been explored. Using data from the MIT Growth and Development Study, a longitudinal study designed to assess the metabolic, dietary, and behavioral factors that predict changes in body composition with growth and development in girls during the adolescent period, the current analysis was undertaken to examine the relation of dairy food intake with relative weight status and percentage body fat (%BF).SUBJECTS: A total of 196 nonobese premenarcheal girls 8–12 y old were enrolled between 1990 and 1993. Girls were followed until 4 y postmenarche.MEASUREMENTS: At each annual follow-up visit, data were collected on %BF by BIA, body mass index (BMI) z-score, and dietary intake (assessed by FFQ). The present analysis is limited to the 178 girls who have at least three annual visits and who have valid anthropometric and food frequency data. In all, 1198 individual measurements were analyzed.RESULTS: At study entry, participants had a mean (s.d.) BMI z-score of −0.27 (0.89), a mean (s.d.) %BF of 23.4 (4.7), and obtained 19.9% (9.2) of daily calories from dairy foods. Linear mixed effects modeling indicated no relationship between BMI z-score or %BF and measures of dairy food or calcium consumption.CONCLUSION: Avoidance of dairy foods due to a possible association with relative body weight is not supported by these findings. We find no evidence that dairy food consumption is associated with BMI z-score or %BF during adolescence, but further research specifically designed to address this question is needed.

Lower Extremity Muscle Mass Predicts Functional Performance in Mobility-Limited Elders

Objectives: This study examined the influence of lower extremity body composition and muscle strength on the severity of mobility-disability in community-dwelling older adults.Methods: Fifty-seven older males and females (age 74.2 ± 7 yrs; BMI 28.9 ± 6 kg/m2) underwent an objective assessment of lower extremity functional performance, the Short Physical Performance Battery test (SPPB). Participants were subsequently classified as having moderate (SPPB score > 7: n = 38) or severe mobility impairments (SPPB score ≤ 7: n = 19). Body composition was assessed using dual-energy X-ray absorptiometry and provided measures of bone mineral density (BMD), total leg lean mass (TLM) and total body fat. Maximal hip extensor muscle strength was estimated using the bilateral leg press exercise. Multiple logistic regression analysis was utilized to identify the significant independent variables that predicted the level of mobility-disability.Results: TLM was a strong independent predictor of the level of functional impairment, after accounting for chronic medical conditions, BMD, body fat, body weight and habitual physical activity. In a separate predictive model, reduced muscle strength was also a significant predictor of severe functional impairment. The severity of mobility-disability was not influenced by gender (p = 0.71). A strong association was elicited between TLM and muscle strength (r = 0.78, p < 0.01).Conclusions: These data suggest that lower extremity muscle mass is an important determinant of physical performance among functionally-limited elders. Such findings may have important implications for the design of suitable strategies to maintain independence in older adults with compromised physical functioning. Additional studies are warranted to assess the efficacy of lifestyle, exercise or therapeutic interventions for increasing lean body mass in this population.

Leptin, Body Composition and Bone Mineral Density in Premenopausal Women

Body weight is known to be associated with bone mass, however, it is unclear whether body composition, as reflected by the percent of total weight that is fat tissue (%fat), is associated with bone mass independently of weight. Fat tissue is metabolically active, and hormonal factors may mediate an association of %fat with bone mass. Leptin, a hormone produced in fat tissue, has recently been shown to be inversely related to bone mass in mice, but whether it is related to human bone mass is uncertain. We sought to investigate the associations of %fat and of serum leptin concentration with bone mineral density (BMD) in a cohort of 153 premenopausal women. BMD measurements of the total hip, lumbar spine and total body as well as body composition were measured by dual energy X-ray absorptiometry (DXA). Serum leptin levels were established using a commercial competitive binding assay. Individually, body weight, %fat and leptin were each positively associated with BMD at all three sites. However, when we examined BMD either as a function of both body weight and %fat together, or as a function of both body weight and leptin together, we found that for a given body weight, BMD appeared to be inversely associated with %fat and similarly appeared to be inversely associated with leptin. When BMD was examined as a function of %fat and leptin together, we found that for a given %fat, leptin appeared to be inversely associated with BMD. In summary, the results of this study suggest that for a given body weight, a higher proportion of fat and a higher serum leptin concentration have negative associations with bone mass in premenopausal women.

A randomized, controlled trial of the role of weaning predictors in clinical decision making*

Objective:Weaning predictors are often incorporated in protocols to predict weaning outcome for patients on mechanical ventilation. The predictors are used as a decision point in protocols to determine whether a patient may advance to a spontaneous breathing trial. The impact of including predictors in a weaning protocol has not been previously studied. We designed a study to determine the effect of including a weaning predictor (frequency-tidal volume ratio, or ƒ/Vt) in a weaning protocol. Design:Randomized, blinded controlled trial. Setting:Academic teaching hospitals. Patients:Three hundred and four patients admitted to intensive care units at three academic teaching hospitals. Interventions:Patients were screened daily for measures of oxygenation, cough and secretions, adequate mental status, and hemodynamic stability. Patients were randomized to two groups; in one group the ƒ/Vt was measured but not used in the decision to wean (n = 151), but in the other group, ƒ/Vt was measured and used, using a threshold of 105 breaths/min/L (n = 153). Patients passing the screen received a 2-hr spontaneous breathing trial. Patients passing the spontaneous breathing trial were eligible for an extubation attempt. Measurements and Main Results:Groups were similar with regard to gender, age, and Acute Physiology and Chronic Health Evaluation II score. The median duration for weaning time was significantly shorter in the group where the weaning predictor was not used (2.0 vs. 3.0 days, p = .04). There was no difference with regard to the extubation failure, in-hospital mortality rate, tracheostomy, or unplanned extubation. Conclusions:Including a weaning predictor (ƒ/Vt) in a protocol prolonged weaning time. In addition, the predictor did not confer survival benefit or reduce the incidence of extubation failure or tracheostomy. The results of this study indicate that ƒ/Vt should not be used routinely in weaning decision making.