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Results for “longitudinal data”

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PubMed2003

Temporal relation between the ADC and DC potential responses to transient focal ischemia in the rat: a Markov chain Monte Carlo simulation analysis.

Markov chain Monte Carlo simulation was used in a reanalysis of the longitudinal data obtained by Harris et al. (J Cereb Blood Flow Metab 20:28-36) in a study of the direct current (DC) potential and apparent diffusion coefficient (ADC) responses to focal ischemia. The main purpose was to provide a formal analysis of the temporal relationship between the ADC and DC responses, to explore the possible involvement of a common latent (driving) process. A Bayesian nonlinear hierarchical random coefficients model was adopted. DC and ADC transition parameter posterior probability distributions were generated using three parallel Markov chains created using the Metropolis algorithm. Particular attention was paid to the within-subject differences between the DC and ADC time course characteristics. The results show that the DC response is biphasic, whereas the ADC exhibits monophasic behavior, and that the two DC components are each distinguishable from the ADC response in their time dependencies. The DC and ADC changes are not, therefore, driven by a common latent process. This work demonstrates a general analytical approach to the multivariate, longitudinal data-processing problem that commonly arises in stroke and other biomedical research.

Animals↗

PubMed2003

Age-specific relationship between CD14 and atopy in a cohort assessed from age 8 to 25 years.

CD14 influences postnatal switching of T helper cell responses. CD14 C-159T has been associated with altered CD14 and IgE levels in cross-sectional studies. Identifying whether associations vary with age requires data from children of the same age followed longitudinally over many years. In this study, an unselected population with extensive longitudinal data was used to test the hypothesis that CD14 C-159T was associated with early-onset atopy. A total of 305 subjects were assessed on up to seven occasions between ages 8 and 25 years by questionnaire, histamine challenge, and skin prick test. For atopy, airway hyperresponsiveness (AHR), and wheeze, each subject was classified as having early onset, late onset, or no disease onset during follow-up. Compared with subjects with -159CT and -159TT, subjects with -159CC had an odds ratio of 2.2 (p = 0.018) for early-onset atopy and an odds ratio of 2.6 (p = 0.019) for early-onset AHR. Cross-sectional analysis showed increased prevalence of -159CC in subjects with atopy and AHR in childhood but not adulthood. These data suggest that the influence of CD14 -159C on the atopic phenotype may be age specific, exerting an effect during midchildhood, which is no longer apparent by early adulthood.

Adolescent↗

PubMed2001

Changes in flow velocity, resistance indices, and cerebral perfusion pressure in the maternal middle cerebral artery distribution during normal pregnancy.

BACKGROUND: There are few longitudinal data currently available detailing the normal changes in maternal cerebral hemodynamics during human pregnancy. This lack of information limits the study of pregnancy-associated cerebrovascular adjustments and, in particular, preeclampsia, where the brain appears to be especially susceptible to ischemic and encephalopathic injury. Our objective was to define the hemodynamic changes, specifically velocity, resistance indices, and cerebral perfusion pressure, in the middle cerebral artery (MCA) distribution of the brain during normal pregnancy. METHODS AND MATERIALS: Transcranial Doppler ultrasound was used to determine the systolic, diastolic and mean blood velocities in the middle cerebral arteries in non-laboring women studied longitudinally during normal gestation. The resistance index (RI), pulsatility index (PI), and cerebral perfusion pressure (CPP) were calculated using the velocity and blood pressure data. Data were analyzed using a longitudinal statistical model incorporating random patient effects and a homoscedastic (compound symmetric) variance-covariance structure over time (gestational age). The predicted mean value (Least Squares Mean), and the 5th and 95th percentiles, were defined for normal pregnancy. RESULTS: MCA systolic velocity decreased (24%) as did the mean velocity (17%). The diastolic velocity did not change significantly. The MCA RI decreased by 19% and the PI decreased by 25%. The MCA CPP increased by 52% between 12 and 40 weeks of gestation. CONCLUSIONS: The normative ranges for MCA velocity, RI, and CPP have been defined in normal human pregnancy using longitudinally collected data. By having a defined normal range, identification of abnormalities in cerebral hemodynamics during pregnancy is now possible, and this may help researchers and clinicians to elucidate etiologies and treatments for pregnancy-related pathophysiologic states such as preeclampsia

Adult↗

PubMed2001

Sexually transmitted infections among HIV infected and HIV uninfected high-risk youth in the REACH study. Reaching for Excellence in Adolescent Care and Health.

OVERVIEW: This review presents the findings of published research in the Reaching for Excellence in Adolescent Care and Health (REACH) Project on sexually transmitted infections (STIs) within the context of the project's scientific agenda. Methods employed in the study for specimen collection, management, and laboratory analysis are presented. This review presents published analyses of cross-sectional data; longitudinal analyses are underway. In addition, baseline prevalence data on selected STIs and sexual risk profiles of the subjects in REACH are presented. High STI rates were evident in both human immunodeficiency virus (HIV) infected and uninfected youth of both genders regardless of sexual orientation. High infection rates at baseline suggest that prevention-oriented programs for risk reduction among adolescents should focus on both HIV infected and at-risk, uninfected youth.

Adolescent↗

PubMed2002

Remission, recovery, relapse, and recurrence in eating disorders: conceptualization and illustration of a validation strategy.

In a consensus-building process a group of experts from 19 European countries (COST Action B6) adapted the terms partial and full remission, relapse, recovery, and recurrence according to principles described by Frank et al. for depression. The empirical validity of the operationalizations was illustrated by longitudinal data on the post treatment course of 233 anorectic and 422 bulimic patients (diagnosed according to DSM-IIIR) from the German Project TR-EAT. These data were collected 2.5 years after admission using the Longitudinal Interval Follow-up Evaluation (LIFE) and statistically explored by survival-analysis. It was demonstrated that these consensus definitions measure what they intend to measure. They open a longitudinal perspective in that one can learn not only whether, but also when and with what probability patients change for the better or worse. Data suggest that persistence of symptom improvement has different implications for anorexia and bulimia nervosa. For example, relapse prevention would be most beneficial for bulimic patients for about 4 months after key symptoms remit, while this would be of less importance for anorexic patients. It is discussed whether and how this longitudinal approach can contribute to an empirically based rationale for targeted and individualized treatment.

Adult↗

PubMed1996

Older adults as a community resource: results from the National Survey of Self-Care and Aging.

Using data collected from the first wave of a longitudinal data set collected in the late fall and winter of 1990-1991, the National Survey of Self-Care and Aging (NSSCA), we examined the extent and type of assistance older people provided to others. Age, gender, and perceived health status were the most consistent predictors of the four types of assistance: personal care, child care, volunteer work, and listening/offering advice and support. Help with instrumental activities of daily living either alone or in combination with other activities of daily living was the most common type of personal care provided.

Activities of Daily Living↗

PubMed2003

On the performance of random-coefficient pattern-mixture models for non-ignorable drop-out.

Random-coefficient pattern-mixture models (RCPMMs) have been proposed for longitudinal data when drop-out is thought to be non-ignorable. An RCPMM is a random-effects model with summaries of drop-out time included among the regressors. The basis of every RCPMM is extrapolation. We review RCPMMs, describe various extrapolation strategies, and show how analyses may be simplified through multiple imputation. Using simulated and real data, we show that alternative RCPMMs that fit equally well may lead to very different estimates for parameters of interest. We also show that minor model misspecification can introduce biases that are quite large relative to standard errors, even in fairly small samples. For many scientific applications, where the form of the population model and nature of the drop-out are unknown, interval estimates from any single RCPMM may suffer from undercoverage because uncertainty about model specification is not taken into account.

Antipsychotic Agents↗

PubMed2026

Early and late CTCAE and patient-reported outcomes following lung cancer radiotherapy: A sex-stratified descriptive analysis from the REQUITE cohort.

BACKGROUND: Long-term prospective data on lung cancer patients treated with radiotherapy are limited, restricting understanding of outcomes and sex-specific characteristics. The multicentre REQUITE study provides standardized follow-up data from an international cohort. METHODS: We analysed longitudinal data from 530 lung cancer patients treated with radical radiotherapy (sequential or concurrent chemoradiotherapy, or stereotactic body radiation therapy [SBRT]) between 2014 and 2017 at 16 centres in Europe and the USA. Healthcare professionals prospectively recorded 21 pulmonary, oesophageal, neurological, cardiac, and skin adverse events using CTCAE v4.0. Patient-reported outcomes assessed symptoms, quality-of-life, fatigue, and physical activity. Adverse event incidence was stratified by sex, radiotherapy technique, chemotherapy administration, smoking status, and other clinical factors. RESULTS: At 12 months, 309 patients were evaluable, with 151 having follow-up beyond one year. Pulmonary adverse events were most frequent (40% grade ≥ 2), mainly dyspnoea and cough. Women had higher rates of oesophagitis, and more frequently reported dysphagia, and chest wall pain, while men experienced a higher frequency of cardiac adverse events. Exploratory subgroup analyses identified significant sex-related differences in grade ≥ 3 pulmonary adverse events following SBRT and in overall grade ≥ 2 oesophageal adverse events among patients with clinical stage I-II and those aged >70 years. Patient-reported outcomes showed persistent fatigue and reduced physical activity, particularly in females. Symptom prevalence and severity varied by sex, age, treatment modality, smoking status, and clinical stage. CONCLUSION: The REQUITE-Lung cohort provides prospectively collected real-world data on radiotherapy-related adverse events in lung cancer patients. This study describes patterns of adverse events and patient-reported outcomes according to sex, age, and treatment characteristics. These findings are hypothesis-generating and may support future validation in independent and pooled datasets.

Patient-reported outcomes↗

PubMed2005

Characteristics of low-level smokers.

Average daily cigarette consumption has decreased, and some evidence suggests that the rate of "some day" smoking has increased; however, relatively little is known about low-level smokers. The present analysis describes and compares low-level versus heavier smokers, using cross-sectional and longitudinal data. Data from the Community Intervention Trial for Smoking Cessation (COMMIT) were used in this analysis. Population-based cross-sectional tobacco use telephone surveys were performed in 22 North American communities in 1988 and 1993, and the prevalence and characteristics of low-level smoking and reasons for quitting are reported from the 1993 prevalence survey. In addition, a cohort of 6,603 smokers was identified in 1988 and interviewed again in 1993 and 2001 to assess patterns of low-level smoking over time and its association with smoking cessation. In 1988, 7.6% were low-level smokers; in 1993, 10.7% were low-level smokers. Compared with heavier smokers, low-level smokers were more likely to be female, older, not married, Black or Hispanic; to have a 4-year college degree; to have no other adult smokers in the household; and to wait longer in the day to have their first cigarette. Low-level smokers also were less likely to report trying to quit because of the expense of smoking or physician advice to quit. They were more likely to try to quit because of trying to set a good example; concern for second-hand smoke; and factors such as bad breath, smell, or the taste of smoking. Those who smoked full-priced premium brands and who worked in a completely smoke-free worksite were more likely to be low-level smokers. Compared with heavier smokers, low-level smokers had similar rates of making a future quit attempt, lower use rates of nicotine replacement therapy, and higher cessation rates. Low-level smokers may be a growing segment of the smoker population and have different characteristics, health risks, and intervention needs compared with their heavier smoking counterparts.

Adult↗

PubMed1995

Self-care and assistance from others in coping with functional status limitations among a national sample of older adults.

Using data from the first wave of a new longitudinal data set collected in the late fall and winter of 1990-1991, the National Survey of Self-Care and Aging (NSSCA), we examined older adults' self-care practices in coping with functional status limitations based on in-person interviews with a national probability sample of 3,485 noninstitutionalized adults aged 65 or older selected from Medicare beneficiary files. A composite score of functional status was calculated to reflect the presence and severity of disability in three dimensions: basic, mobility, and instrumental activities of daily living. Three types of self-care coping strategies were defined: use of equipment or devices, changes in behavior, and modifications in one's environment. National estimates of self-care practices, assistance from others, and functional status measures were presented. Data revealed that the likelihood of engaging in self-care coping strategies increased as the severity of disability increased, except among the most severely disabled. Generally, those receiving assistance from others were more likely to engage in self-care activities, suggesting that receiving assistance supplements, rather than supplants, self-care coping strategies.

Activities of Daily Living↗

PubMed2004

Mycophenolate mofetil in IgA nephropathy: results of a 3-year prospective placebo-controlled randomized study.

BACKGROUND: Because humoral immunity is believed to play a pivotal role in the pathogenesis of IgA nephropathy (IgAN), a prospective placebo-controlled randomized study was started in patients with IgAN using mycophenolate mofetil (MMF). METHODS: A total of 34 patients with IgAN were treated with salt intake restriction, angiotensin-converting enzyme (ACE) inhibition and MMF 2 g per day (N= 21) or placebo (N= 13). After 36 months of follow-up clinical, biochemical, and radiologic data were analyzed using linear mixed models for longitudinal data and Kaplan-Meier survival analysis. RESULTS: Therapy had to be stopped prematurely in five patients. Two patients (MMF group) evolved to end-stage renal disease (ESRD). There was no difference between groups in the percentage of patients with a decrease of 25% or more in the inulin clearance or with a serum creatinine increase of 50% or more over 3 years. There was also no significant difference between groups in annualized rate of change of serum creatinine, computed by linear regression analysis. No significant difference was noted between groups for inulin clearance, serum creatinine, proteinuria, blood pressure, or other parameters of renal function. Hemoglobin and C-reactive protein were significantly lower in the MMF group compared with the placebo group. As a function of time, a significant decline in both groups was noted of proteinuria, parenchymal thickness of the kidneys and C3d. CONCLUSION: In patients with IgAN at risk for progressive disease, no beneficial effect of 3-year treatment with MMF 2 g per day could be demonstrated on renal function/outcome or proteinuria. However, larger randomized studies are needed to confirm or reject these results.

Adult↗

PubMed2005

Household income histories and child mental health trajectories.

Although it is widely accepted that low household income is associated with worse child mental health, less is known about whether income histories, often differentiated into stable and dynamic components, also matter. Using longitudinal data from the Child Supplement of the National Longitudinal Study of Youth, comprising the repeated measures of children ages 4 to 14 from 1986 to 1998 inclusive, I estimate generalized linear mixed models to evaluate the influence of household income histories on child depression and antisocial behavior over time. Results indicate that, at initial interview, low household income is associated with higher levels of depression and antisocial behavior; subsequent improvements in household income reduce child mental health problems. Further, the effect of initial household income on the rate of change in child depression attenuates as children grow older, whereas for antisocial behavior the effect of initial household income becomes stronger over time. These findings highlight the importance of understanding the ways in which children are influenced by their families' income histories.

Adolescent↗

PubMed1996

Structural time series models in medicine.

Structural time series models are formulated in terms of components, such as trends, seasonals and cycles, which have a direct interpretation. This article describes such models and gives examples of how they can be applied in medicine. Univariate models are considered first, and then extended to include explanatory variables and interventions. Multivariate models are then shown to provide a framework for modelling longitudinal data and for carrying out intervention analysis with control groups. The final sections deal with data irregularities and non-Gaussian observations.

Bias↗

PubMedDate not supplied

Age differences in personality structure revisited: Studies in validity, stability, and change.

Construct validity and longitudinal stability evidence for three cluster dimensions of personality identified as Anxiety, Extraversion, and Openness is examined in a sample of adult males. Correlations with Allport-Vernon-Lindsay Value scales, Cornell Medical Index scores, Eysenck E and N scales, and factors from the SVIB are presented in support of the interpretation of the three clusters. Nine-year longitudinal evidence of stability is presented for Anxiety and Extraversion scores. Previous evidence for change in the structure of Openness to Experience is reconsidered in the light of eleven-year longitudinal data. While the earlier structural differences were not longitudinally replicated, a pattern of external correlates provided evidence for validity of an Openness dimension. Finally, the structural approach to personality development is illustrated by examining the differing relations between field-dependence and tendermindedness in younger and older men.

Adult↗

PubMedDate not supplied

Neighborhood, family, and child predictors of childhood injury in Canada.

OBJECTIVE: To examine independent and combined effects of child, family and neighborhood on medically attended childhood injuries. METHODS: Logistic modeling of longitudinal data (n=9796) from the Census Linked National Longitudinal Survey of Children and Youth. RESULTS: Child age and gender were strong predictors of injuries. Smaller effects were found for parenting, neighborhood cohesion among difficult children less than 2 years old, and neighborhood disadvantage among aggressive children 2-3 years old. CONCLUSION: Neighborhood in addition to parenting can affect injury risk. Further research is needed into the influence of neighborhood disadvantage and the processes of neighbor's cohesion at different childhood stages.

Adolescent↗

PubMed1986

A profile of functionally impaired elderly persons living in the community.

The Health Care Financing Administration, in cooperation with other agencies of the Department of Health and Human Services, conducted surveys in 1982 and 1984 designed to develop a better understanding of the number and circumstances of functionally impaired elderly persons living in the community. This report is based on data from the 1982 Long-Term Care Survey. There were approximately 5 million functionally impaired elderly persons living in the community in 1982. The data show that functionally impaired persons in the community are older, are more often female, have lower incomes, and have a larger proportion of black people than the general elderly population. The data also provide baseline information on what functional impairments are prevalent among them, what means they use to cope with the limitations, and from whom they receive help. The baselines data gathered in 1982 will be supplemented by longitudinal data gathered in the 1984 Long-Term Care Survey.

Activities of Daily Living↗

PubMed1993

Results of liver transplantation in diabetic recipients.

BACKGROUND: The results of orthotopic liver transplantation (OLTx) in patients with diabetes mellitus (DM) are not well defined. METHODS: Between 1985 and 1991, 45 adult patients with pretransplantation DM (5 type I, 40 type II) underwent OLTx at our center as identified by retrospective chart review. We compared this diabetic recipient group to a case-control nondiabetic group matched for age, gender, primary liver disease, weight, and timing of OLTx. A total of 30 variables were collected and analyzed with McNemar's test for categorical data, paired t tests for continuous data, and survival and repeated measures analysis for longitudinal data. RESULTS: No differences between diabetic and nondiabetic recipients were noted in patient or graft survival, the incidence or severity of rejection, blood transfusions, operative complications, readmissions, major infections, or number of hospital days after OLTx. However, the incidence of minor bacterial (p = 0.046) and minor fungal (p = 0.035) infections were higher in the DM group. Serum blood urea nitrogen (p = 0.02) and creatinine (p = 0.03) levels were also higher in patients with diabetes versus control patients during the first year after OLTx. CONCLUSIONS: In carefully selected patients with pretransplantation DM, OLTx can be accomplished with results similar to nondiabetic recipients in spite of a higher incidence of minor infections and renal dysfunction.

Diabetes Complications↗

PubMedDate not supplied

A comparative study of three methods for analysing longitudinal pulmonary function data.

We compare three methods of longitudinal analysis of pulmonary function data. Our data set is taken from a study of exposure to toluene diisocyanate (TDI) vapours in a new manufacturing plant. The first two methods are a two-stage weighted regression method and maximum likelihood estimation via the EM algorithm, and these give very similar results. The third method, regression with an autoregressive error structure, was not successfully implemented, and in our view needs better documentation.

Adult↗