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Food insecurity affects school children's academic performance, weight gain, and social skills.

Food insecurity has been associated with diverse developmental consequences for U.S. children primarily from cross-sectional studies. We used longitudinal data to investigate how food insecurity over time related to changes in reading and mathematics test performance, weight and BMI, and social skills in children. Data were from the Early Childhood Longitudinal Study-Kindergarten Cohort, a prospective sample of approximately 21,000 nationally representative children entering kindergarten in 1998 and followed through 3rd grade. Food insecurity was measured by parent interview using a modification of the USDA module in which households were classified as food insecure if they reported > or =1 affirmative response in the past year. Households were grouped into 4 categories based on the temporal occurrence of food insecurity in kindergarten and 3rd grade. Children's academic performance, height, and weight were assessed directly. Children's social skills were reported by teachers. Analyses examined the effects of modified food insecurity on changes in child outcomes using lagged, dynamic, and difference (i.e., fixed-effects) models and controlling for child and household contextual variables. In lagged models, food insecurity was predictive of poor developmental trajectories in children before controlling for other variables. Food insecurity thus serves as an important marker for identifying children who fare worse in terms of subsequent development. In all models with controls, food insecurity was associated with outcomes, and associations differed by gender. This study provides the strongest empirical evidence to date that food insecurity is linked to specific developmental consequences for children, and that these consequences may be both nutritional and nonnutritional.

Attitude to Health↗

Faculty renewal: modeling the impact of the end of mandatory retirement in the University of California medical schools.

The Age Discrimination in Employment Act was amended in 1986 to remove age-determined mandatory retirement for nearly all employees. The present study was prompted by the concern that if medical school faculty failed to retire, there would be no positions available for new faculty. The author used 1984-85 data on both tenure-track and non-tenure-track faculty of the five medical schools of the University of California (UC) to make projections, over 20 years, of faculty age distributions and available positions, at several possible growth rates and delays in retirement age. Association of American Medical Colleges data on all U.S. medical school faculty in 1980 were used to show that the UC data were not exceptional. Acknowledging the various assumptions used in manipulating the data and the need to examine longitudinal data on faculty age, growth, turnover, and retirement to make more realistic projections, the author demonstrates that the impact of delaying retirement by several years would be minimal. Because of this conclusion and also the inevitable aging of the faculty resulting from the slowed growth of medical schools, academic institutions should pay more attention to maintaining the vitality and productivity of their individual faculty members, regardless of age.

Age Factors↗

Long-term changes in body potassium concentration and dose from 40K for a Japanese adult male group.

Total body potassium has been measured for a Japanese adult male group using two whole-body counters. The total body potassium data were analyzed to present the longitudinal data on body potassium concentration in aging individuals. The data for each individual showed that potassium concentration decreased linearly with age from 30 y to 60 y of age. The average decrease rate was -0.0154 +/- 0.0049 g K kg body wt(-1) y(-1). On the other hand, a subject group for each of the 23 years (1975-1998) of the study was divided into three age groups. The same age groups were followed with the course of time to analyze changes in potassium concentration due to other factors besides age. The follow-up study of the same age groups indicated that the average potassium concentration decreased with the course of the 23-y study and that the decrease was due to other factors besides age. The decrease in the average potassium concentration for study subjects is the major cause of the decrease in the average annual dose from 40K. The average annual dose for subjects aged 30-59 y was 194 muGy in 1975, changing to 166 muGy in 1998. The decrease in the average annual dose was about 14% over the 23-y study period.

Adult↗

Nonsurgical factors that influence the outcome of bariatric surgery: a review.

OBJECTIVE: Severe obesity (ie, at least 100% overweight or body mass index > or =40 kg/m2) is associated with significant morbidity and increased mortality. It is apparently becoming more common in this country. Conventional weight-loss treatments are usually ineffective for severe obesity and bariatric surgery is recommended as a treatment option. However, longitudinal data on the long-term outcome of bariatric surgery are sparse. Available data indicate that the outcome of bariatric surgery, although usually favorable in the short term, is variable and weight regain sometimes occurs at 2 years after surgery. The objective of this study is to present a review of the outcome of bariatric surgery in three areas: weight loss and improvement in health status, changes in eating behavior, and psychosocial adjustment. The study will also review how eating behavior, energy metabolism, and psychosocial functioning may affect the outcome of bariatric surgery. Suggestions for additional research in these areas are made. METHOD: Literature review. RESULTS: On average, most patients lose 60% of excess weight after gastric bypass and 40% after vertical banded gastroplasty. In about 30% of patients, weight regain occurs at 18 months to 2 years after surgery. Binge eating behavior, which is common among the morbidly obese, may recur after surgery and is associated with weight regain. Energy metabolism may affect the outcome of bariatric surgery, but it has not been systematically studied in this population. Presurgery psychosocial functioning does not seem to affect the outcome of surgery, and psychosocial outcome is generally encouraging over the short term, but there are reports of poor adjustment after weight loss, including alcohol abuse and suicide. CONCLUSIONS: Factors leading to poor outcome of bariatric surgery, such as binge eating and lowered energy metabolism, should be studied to improve patient selection and outcome. Long-term outcome data on psychosocial functioning are lacking. Longitudinal studies to examine the long-term outcome of bariatric surgery and the prognostic indicators are needed.

Feeding Behavior↗

Continuing HIV transmission among injection drug users in Eastern Central Canada: the SurvUDI Study, 1995 to 2000.

OBJECTIVE: To document HIV prevalence/incidence trends from 1995-2000 and associated risk factors among injection drug users (IDUs) in Eastern Central Canada as an indication of harm reduction strategy effectiveness. METHODS: Nonnominal cross-sectional data (one-time participants) and longitudinal data (repeat participants) were collected using convenience sampling. Participants provided informed consent for face-to-face interviews focused on injection drug use and sexual practices during the previous 6 months; oral fluid samples were taken for HIV testing by enzyme immunoassay. Unique encrypted codes for initially HIV-negative repeat participants permitted incidence rate calculations. RESULTS: In all, 6387 IDUs (median age, 31 years; range, 13-67; males, 73.5%) participated on 9724 occasions. HIV prevalence ranged from 4.7% (95% confidence interval [CI], 2.9-6.5) in semiurban areas to 20.1% (95% CI, 17.6-22.7) in Ottawa, Ontario. HIV incidence was 6.0 (95%CI, 4.5-7.6) per 100 person-years (py) in Montréal, Québec, 3.2 (95% CI, 2.2-4.2) per 100 py in Québec City and 7.0 (95% CI, 4.1-9.8) per 100 py in Ottawa/Hull. Reusing other IDUs' needles was reported by 38.4%. In multivariate logistic regression, IDUs injecting for 6 or more years were more likely to be HIV positive, particularly if cocaine was the predominant drug injected. Multivariate Cox regression revealed higher HIV incidence among those who predominantly injected cocaine, reused others' needles, had injected 6 years or more, injected with strangers, or were men reporting commercial sex work. CONCLUSIONS: These results reveal a volatile situation of continuing HIV transmission among IDUs in Eastern Central Canada.

AIDS Serodiagnosis↗

An estimation method for the semiparametric mixed effects model.

A semiparametric mixed effects regression model is proposed for the analysis of clustered or longitudinal data with continuous, ordinal, or binary outcome. The common assumption of Gaussian random effects is relaxed by using a predictive recursion method (Newton and Zhang, 1999) to provide a nonparametric smooth density estimate. A new strategy is introduced to accelerate the algorithm. Parameter estimates are obtained by maximizing the marginal profile likelihood by Powell's conjugate direction search method. Monte Carlo results are presented to show that the method can improve the mean squared error of the fixed effects estimators when the random effects distribution is not Gaussian. The usefulness of visualizing the random effects density itself is illustrated in the analysis of data from the Wisconsin Sleep Survey. The proposed estimation procedure is computationally feasible for quite large data sets.

Biometry↗

Fostering hope in terminally ill patients.

AIM: To investigate the meaning of hope, identify strategies that terminally ill patients use in maintaining and fostering hope during the final stage of life, explore changes in hope during the dying trajectory and investigate whether the results of a North American study by Herth (1990a), that explored the meaning of hope and identified strategies to promote it, could be replicated in England. METHOD: A total of 16 adults receiving palliative care took part in the study. Cross-sectional data were collected on all participants. Longitudinal data were collected on four of the 16 participants using methodological triangulation, which encompassed a background data form, the Herth Hope Index and a semi-structured interview (Herth 1990a). FINDINGS: Hope remained present regardless of nearness to death. Seven hope-fostering categories and three hope-hindering categories were identified based on interview responses. CONCLUSION: The study supported Herth's original study (Herth 1990a), and could serve as a guide to individual practitioners and the nursing team in developing an environment and interventions that foster hope in people receiving palliative care in any setting.

Adaptation, Psychological↗

Cost-utility analysis of interferon beta-1B in secondary progressive multiple sclerosis using natural history disease data.

OBJECTIVES: Different cost-effectiveness analyses have been presented for interferon beta-1b (IFNB) in the treatment of secondary progressive multiple sclerosis (SPMS). All studies have used modeling techniques since any effect on progression of disability achieved during a clinical trial will last beyond the trial. Different approaches to extrapolation have been taken, but generally they have been based on disease progression and relapse rates in clinical trials. The problem with this approach is that the population in clinical trials is a selected group of patients, which has the potential to bias results. A better method for extrapolation is to use epidemiologic data. The objective of this study is to incorporate natural history data for MS into a previously presented cost-utility model and to compare the two methods of extrapolation. METHODS: Clinical trial data were used to model disease progression during the first 3 years in the model. To extrapolate beyond the trial (10 years), data on progression of disability were available from a geographically based epidemiologic study of the natural history of MS in Canada. There were 568 patients who had converted to SPMS during the follow-up that were included in the data set. Mean costs and utilities for each Markov state were calculated from a population-based cross-sectional study in Sweden. RESULTS: The extrapolation using clinical trial data appears to have underestimated the progression of disability in the long term and thus also the potential benefit of treatment. Using the epidemiologic data, the incremental cost per QALY is SEK 257,000 (US $25,700; US $1 = SEK 10; November 2000) when all costs (direct, informal care, and indirect) are included (discounted 3%). This compares to SEK 342,000 in the previous model. The lower cost-effectiveness ratio is mostly due to a larger QALY gain with treatment than in the previous model (0.217 compared with 0.162). CONCLUSIONS: Cost-effectiveness analysis in SPMS requires that the effect of treatment beyond clinical trials be included. The method of extrapolation clearly affects the results, and when available, epidemiologic data should be used. Using the longitudinal data from Canada, the cost-utility ratios for IFNB-1b in the treatment of SPMS appear well within the acceptable range.

Adjuvants, Immunologic↗

[Assessment of the efficiency of population policy measures].

This article is concerned with the relative effectiveness of various population policy measures. "The data sources [for] analysing efficiency (vital statistics, census data, longitudinal and retrospective analysis of fertility, data of public opinion research) and the possible methods (standardization, trend analysis, experimental samples, number of years spent for contraception by co-habitants, component forecasting approach, the analysis of the reproduction process, regression analysis, simulation models) are reviewed." (summary in ENG, RUS)

Data Collection↗

Problems and solutions in longitudinal and experimental treatment studies of child psychopathology and delinquency.

This article identifies questions in child psychopathology and delinquency that can best be answered by using longitudinal data and discusses the advantages and problems of longitudinal studies. The article also reviews methodological issues arising in longitudinal research on child psychopathology and proposes solutions to problems. Retrospective and prospective designs are contrasted with the accelerated longitudinal design. It is concluded that more longitudinal studies of child psychopathology including experimental treatment interventions are needed, with repeated data collection from a variety of sources and several years of data before and after the interventions. Such studies, in addition to the traditional longitudinal studies, are likely to improve the understanding of child psychopathology and of factors that influence and reduce serious outcomes for children and adolescents.

Adolescent↗

GEE estimation of a misspecified time-varying covariate: an example with the effect of alcoholism treatment on medical utilization.

The generalized estimation equation (GEE) method is widely used in longitudinal data analysis, particularly when the outcome variable is non-Gaussian distributed. Under mild regulatory conditions, the parameter estimates are consistent and their asymptotic variances are efficient. In an observational study focusing on alcoholism patients, we applied the GEE method to longitudinal count data from medical utilization records from a large national managed care organization. The health services research question was whether there was a change in medical utilization for patients after engaging in alcoholism treatment as compared to before treatment. Thus, the main effect of interest was a time-varying covariate indicating whether the patient had undergone treatment yet or not. GEE under five different working correlations was employed and mixed results regarding the significance of the treatment effect were found. Because of the large sample size, i.e. 8485 patients with an average of 46 repeated measurements per patient, differences across the estimates produced by the different working correlation structures was suspicious. It is shown that these differences are maybe caused by the fact that the time-varying covariate in the marginal mean model is misspecified. A simulation study is performed to demonstrate that misspecification of the time-varying covariate in the marginal mean structure can cause differences in GEE results across various choices of working correlation structure.

Adult↗

Somatic development in cleidocranial dysplasia.

As part of a more comprehensive investigation of general and craniofacial development in cleidocranial dysplasia (CCD), the present study describes general somatic development and analyzes longitudinal growth of 17 patients (seven males, ten females, aged 5-46 years) with CCD. Eleven were followed longitudinally. Data included family history, anthropometric measurements, and radiographs of the right hand and forearm. Height and radius length were significantly decreased, being most pronounced in females. The longitudinal growth data showed growth retardation and slightly retarded skeletal maturity throughout childhood. Metacarpophalangeal pattern profile analysis demonstrated great variation in bone lengths, presumably resulting from extra epiphyses in the 2nd and 5th metacarpals and from multiple cone-shaped epiphyses. Findings of the present study support the view that CCD is a generalized skeletal dysplasia.

Adolescent↗

Functional data analysis with application to periodically stimulated foetal heart rate data. I: functional regression.

Functional regression is used to model longitudinal data where the number of measurements on the functional covariate is much greater than the number of subjects in the study. Thus, functional regression can be thought of as singular longitudinal analysis. We have modified existing functional regression techniques to the case of a functional covariate with a repeated stimulus. We applied this modified functional regression to periodically stimulated foetal heart rates. The heart rate tracings were used as a predictor of the child's psychomotor development at approximately 18 months of age. In the past, this type of data has been analysed using the partially subjective concept of habituation. By using the entire heart rate tracings through functional regression, we have the advantage that habituation does not need to be defined and all available information is used to predict later child development.

Adult↗

Assessing response profiles from incomplete longitudinal clinical trial data under regulatory considerations.

Treatment effects are often evaluated by comparing change over time in outcome measures. However, valid analyses of longitudinal data can be problematic, particularly when some data are missing for reasons related to the outcome. In choosing the primary analysis for confirmatory clinical trials, regulatory agencies have for decades favored the last observation carried forward (LOCF) approach for imputing missing values. Many advances in statistical methodology, and also in our ability to implement those methods, have been made in recent years. The characteristics of data from acute phase clinical trials can be exploited to develop an appropriate analysis for assessing response profiles in a regulatory setting. These data characteristics and regulatory considerations will be reviewed. Approaches for handling missing data are compared along with options for modeling time effects and correlations between repeated measurements. Theory and empirical evidence are utilized to support the proposal that likelihood-based mixed-effects model repeated measures (MMRM) approaches, based on the missing at random assumption, provide superior control of Type I and Type II errors when compared with the traditional LOCF approach, which is based on the more restrictive missing completely at random assumption. It is further reasoned that in acute phase clinical trials, unstructured modeling of time trends and within-subject error correlations may be preferred.

Clinical Trials as Topic↗

Do quality of life assessments make a difference in the evaluation of cancer treatments?

The question posed by this set of quality of life papers is whether or not quality of life assessments in cancer clinical trials help evaluate the effects of cancer treatment on patient functioning. In this discussion, missing data problems, particularly those commonly found in advanced stage disease trials, are highlighted. Researchers are encouraged to investigate the extent of bias associated with missing data and to select analysis approaches accordingly. In the worst case, it may not be possible to analyze data longitudinally; descriptive or graphical portrayals of the data may be more appropriate. The importance of instrument reliability (minimizing measurement error) is emphasized for clinical trials research, particularly with respect to enhancing a trial's ability to detect quality of life differences by treatment arm. One strategy for addressing missing data is evaluated with respect to its impact on the measurement properties of the quality of life questionnaire. Clinical trials groups have been successful in obtaining quality of life data in multi-site settings and patients, by and large, appreciate the effort to include a systematic and standardized report of the effects of treatment on their functioning.

Bias↗

Using clinical and functional data for quality improvement in outcomes measurement consortia.

BACKGROUND: Using standardized measures, American Group Practice Association care providers compiled a national database from which patients could be tracked, allowing for epidemiologic comparisons among treatments, sources of care, and results. Within five years, the consortia expanded from 6 to 55 clinics and from a focus on total hip replacement surgery to eight different health conditions. DATA COLLECTION PROCESS: Reflecting areas of significant public concern, high prevalence, high cost, or research needs, both patient- and provider-source data are collected at group practices at standardized intervals: 6 months, 12 months, and annually thereafter. OUTCOMES DATA MANAGEMENT AND REPORTING: A readily adaptable database infrastructure allows data-collection tools to adapt individual questions to changing conditions in the health care environment while maintaining the integrity of the whole structure. Aggregate-level reports complement individual clinics' own internal analysis efforts by providing a context for the interpretation of results. CASE STUDIES: In a total hip replacement consortium (including more than 2,300 patients), early findings have shown that patients do not fully recover from surgery as quickly as they themselves anticipated. In the cataract consortium, data scores on near, distant, day, night, glare, and overall vision scales improve considerably after cataract surgery, giving clinics a new tool to monitor and improve performance. In the asthma consortium, one clinic reevaluated the distribution of peak flow meters and the reasons for their underuse after noting the low number of patients in the clinic that had peak flow meters. LESSONS LEARNED: Provider participation in study design, instrumentation, data analysis, and feedback is important, and physician buy-in and support are critical to the success of any outcomes initiative. Missing data are the greatest limitations of a longitudinal data set and are difficult to collect through follow-up. There is still much to be learned about what functional status and well being measures can show about the relationship between health care services and patient health.

Asthma↗

Moderate alcohol consumption and heart disease.

OBJECTIVES: This article examines patterns of alcohol consumption in relation to a subsequent new diagnosis of or death from heart disease. DATA SOURCES: The analysis is based on longitudinal data from the first three cycles of the National Population Health Survey (NPHS), conducted by Statistics Canada in 1994/95, 1996/97 and 1998/99. The data are from a sample of 3,379 women and 2,635 men from the household population, who, in 1994/95, were aged 40 or older and reported that they had not been diagnosed with heart disease. Cause of death was established with information from the Canadian Mortality Database. ANALYTICAL TECHNIQUES: Descriptive data were produced using bivariate frequencies. Multiple logistic regression was used to examine associations between level of alcohol consumption reported in 1994/95 and a subsequent diagnosis of or death from heart disease. MAIN RESULTS: Women reporting moderate alcohol consumption--two to nine drinks in the past week--had significantly lower odds of receiving a new diagnosis of or dying from heart disease between 1994/95 and 1998/99, compared with women who reported lifetime abstinence. No association between alcohol consumption and subsequent heart disease emerged for men.

Adult↗

Changes in social support in relation to seniors' use of home care.

OBJECTIVES: This article examines seniors' entry into government-supported home care in relation to changes in levels of social support and in living arrangements. DATA SOURCE: The analysis is based on longitudinal data from the household component of the first two cycles of the National Population Health Survey, conducted by Statistics Canada in 1994/95 and 1996/97. Data from a sample of 2,044 people aged 65 or older who were followed prospectively were weighted to represent 2.7 million household-dwelling seniors. ANALYTICAL TECHNIQUES: Descriptive data were produced using bivariate frequencies. A multiple logistic regression model was used to examine associations between home care entry and changes in levels of social support and in living arrangements, while controlling for demographic and health-related factors. MAIN RESULTS: Among people aged 65 or older who did not receive government-supported home care in 1994/95, an estimated 7% (192,000) were receiving these services in 1996/97. Changes in social support and in living arrangements between 1994/95 and 1996/97 were significantly associated with home care entry.

Activities of Daily Living↗