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Results for “longitudinal data”

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PubMed2003

Tracking cognitive functioning over time: ten-year longitudinal data from a community-based study.

Over 10 years, a community-based sample age 65> or = years, with a starting cohort size of 1,206, was assessed biennially with the Mini-Mental State Exam; the Consortium to Establish a Registry for Alzheimer's Disease battery; Immediate and Delayed Recall of a Story; Verbal Fluency for P and S, Fruits and Animals; Clock Drawing; Temporal Orientation; and Trail Making tests. We report distributions of scores over time, at each wave, in (a) all individuals who were assessed at that wave, whether or not they participated in all waves, and (b) the Survivor subgroup of 425 participants who completed all tests at all 5 waves. Scores and factor structures remained remarkably stable over the study period. The most marked decline over time was seen on the Trail Making tests. As the survivors are de facto a largely healthy and motivated group, their data can be considered population-based healthy norms and may serve as a reference for other studies conducting repeated evaluations using the same tests.

Aged↗

PubMed2004

An empirical study of the predictive validity of number grades in medical school using 3 decades of longitudinal data: implications for a grading system.

Context It is important to establish the predictive validity of medical school grades. The strength of predictive validity and the ability to identify at-risk students in medical schools depends upon assessment systems such as number grades, pass/fail (P/F) or honours/pass/fail (H/P/F) systems. Objective This study was designed to examine the predictive validity of number grades in medical school, and to determine whether any important information is lost in a shift from number to P/F and H/P/F grading systems. Subjects The participants in this prospective, longitudinal study were 6656 medical students who studied at Jefferson Medical College over 3 decades. They were grouped into 10 deciles based on their number grades in Year 1 of medical school. Methods Participants were compared on academic accomplishments in Years 2 and 3 of medical school, medical school class rank, delayed graduation and attrition, performance on medical licensing examinations and clinical competence ratings in the first postgraduate year. Results Results supported the short- and longterm predictive validity of the number grades. Ratings of clinical competence beyond medical school were predicted by number grades in medical school. We demonstrated that small differences in number grades are statistically meaningful, and that important information for identifying students in need of remedial education is lost when students who narrowly meet faculty's expectations are included with the rest of the class in a broad 'pass' category. Conclusions The findings refute the argument that knowledge of sciences basic to medicine is not critical to subsequent performance in medical school and beyond if an appropriate evaluation system is used. Furthermore, the results of this study raise questions about abandoning number grades in favour of a pass/fail system. Consideration of these findings in policy decisions regarding assessment systems of medical students is recommended.

Achievement↗

PubMed2001

A prospective study of quality of life in head and neck cancer patients. Part II: Longitudinal data.

OBJECTIVES: To evaluate the health-related quality of life (HRQL) of patients with head and neck cancer during and after treatment with radiotherapy, surgery, and chemotherapy. STUDY DESIGN: Prospective, descriptive study. METHODS: All new patients in four institutions in Norway and Sweden were asked to participate. Health-related quality of life was assessed at baseline and at 1, 2, 3, 6, and 12 months after start of treatment by means of the European Organization for Research and Treatment of Cancer (EORTC) Core Quality of Life Questionnaire and the EORTC head and neck cancer-specific questionnaire. Baseline results are described elsewhere; longitudinal results are presented in the current article. Three hundred fifty-seven patients with cancer in the oral cavity, pharynx, larynx, nose, sinuses, and salivary glands and neck node metastases from unknown primaries filled in the questionnaires at baseline. RESULTS: Seventy-eight percent of the patients who were alive after 12 months filled in all questionnaires (218/280). The general trend was that HRQL deteriorated significantly during treatment, followed by a slow recovery until the 12-month follow-up with few exceptions (senses, dry mouth, and sexuality). Patients who later died reported worse HRQL at each assessment point compared with patients who filled in all six questionnaires, whereas those who dropped out of the study for other reasons were quite similar to patients who filled in all questionnaires. The patients with pharyngeal cancer in general reported worse HRQL compared with the other groups and did not reach pretreatment values in several domains. Stage was also an important factor for HRQL in patients with head and neck cancer. CONCLUSION: Detailed knowledge about the differences between groups and changes over time may aid us in the communication with patients and in the design of intervention studies focusing on improvement of the support and rehabilitation of patients with head and neck cancer.

Adult↗

PubMed2003

A modelling strategy for the analysis of clinical trials with partly missing longitudinal data.

Standard statistical analyses of randomized controlled trials with partially missing outcome data often exclude valuable information from individuals with incomplete follow-up. This may lead to biased estimates of the intervention effect and loss of precision. We consider a randomized trial with a repeatedly measured outcome, in which the value of the outcome on the final occasion is of primary interest. We propose a modelling strategy in which the model is successively extended to include baseline values of the outcome, then intermediate values of the outcome, and finally values of other outcome variables. Likelihood-based estimation of random effects models is used, allowing the incorporation of data from individuals with some missing outcomes. Each estimated intervention effect is free of non-response bias under a different missing-at-random assumption. These assumptions become more plausible as the more complex models are fitted, so we propose using the trend in estimated intervention effects to assess the nature of any non-response bias. The methods are applied to data from a trial comparing intensive case management with standard case management for severely psychotic patients. All models give similar estimates of the intervention effect and we conclude that non-response bias is likely to be small.

Humans↗

PubMed1988

Blood lead and blood pressure: analysis of cross-sectional and longitudinal data from Canada.

Analysis of data collected during the Canada Health Survey of 1978-1979 indicated a positive relationship between blood lead and blood pressure, but so weak that the range of lead-related variation among members of the general public was estimated to be at most 3.0 mm Hg of diastolic pressure. Even so, a blood lead level in excess of the median value of 10 micrograms/dL entailed a 37% higher risk of having diastolic pressure above 90 mm Hg. In a longitudinal study of lead foundry workers, an association was found between short-term changes in an individual's blood lead level and contemporary changes in diastolic pressure; this remained significant after allowance for age (or time) trends and for effects attributable to changes in body weight. Short-term changes in urinary cadmium levels were similarly predictive of diastolic pressure.

Adult↗

PubMed2002

[Mortality of 1880-1980 generations in Switzerland: a rereading of evolution of mortality based on longitudinal data].

OBJECTIVES: Seek to explain the declining mortality rates observed in Switzerland using a different approach from conventional period analyses. METHODS: Analysis of the mortality rates for cohorts born between 1880 and 1980 in Switzerland. RESULTS: While the mortality transition was a constant feature of the 20th century, mortality receded most sharply among the 1900 to 1940 birth cohorts. Life expectancy gains were much lower for the pre-1900 cohorts, while early trends for the post-1940 cohorts point to a slowdown in the rate of mortality decline. These findings may be connected with the social and health conditions in which the different cohorts lived. CONCLUSION: In contrast to the cross-sectional analysis, the longitudinal approach shows that the decline in mortality suddenly stops with the 1940 cohort.

Adolescent↗

PubMed1998

Hyperfiltration in African-American patients with type 2 diabetes. Cross-sectional and longitudinal data.

OBJECTIVE: Hyperfiltration may play a role in the development of diabetic nephropathy. African-American patients with diabetes have more than a fourfold increase in end-stage renal disease. The purpose of this study is to evaluate the impact of hyperfiltration on renal function in African-American patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: Renal function of 194 African-American patients with diagnosed type 2 diabetes from 1 month to 36 years was assessed by studies of isotopic glomerular filtration rate (GFR), serum creatinine, creatinine clearance, and 24-h urinary albumin excretion rates. Thirty-four patients with a duration of diagnosed type 2 diabetes from 1 month to 10 years were found to have hyperfiltration (GFR > or = 140 ml.min-1.1.73 m-2). Fifteen of these patients received longitudinal follow-up of renal function for as long as 15 years after the initial study. RESULTS: Hyperfiltration is present in 15 (36%) of 42 patients whose duration of diagnosed type 2 diabetes is < 1 year, and it persists for up to 10 years in 14-20% of patients with diagnosed type 2 diabetes. Patients with hyperfiltration are younger than their counterparts without hyperfiltration when matched for duration of diagnosed diabetes. When followed over time, those patients with hyperfiltration were not more likely to develop impaired renal function as measured by GFR or creatinine clearance. CONCLUSIONS: Hyperfiltration does not identify patients at risk for deterioration in renal function.

Adult↗

PubMed1992

Modelling balanced longitudinal data: maximum likelihood estimation and analysis of variance.

For linear models, assuming a within-experimental-units covariance structure that incorporates errors of measurement, serial correlation, and variation between units, results on explicit estimation of regression parameters are used to simplify maximum likelihood estimation of covariance parameters. The use of an analysis of variance table as a simpler alternative to likelihood inference is illustrated with two examples.

Analysis of Variance↗

PubMed1999

Evaluating the vocational rehabilitation program using longitudinal data. Evidence for a quasiexperimental research design.

The study presents benefit-cost ratios for 14 disability cohorts served by the Vocational Rehabilitation (VR) Program. The earnings impacts are estimated in a quasiexperimental framework using an internal comparison group. The earnings data are from a unique national panel constructed by linking client data of the Rehabilitative Services Administration with earnings histories from the Social Security Administration. These earnings data accommodate a series of statistical tests that allow us to identify and control for the presence of selection bias when estimating treatment impacts. The results indicate that the VR program is cost-effective in general, although not universally so across specific disabilities.

Adult↗

PubMed2005

[On the prognosis of hip fractures. Assessment of mortality after hip fractures by analyzing overlapping segments of longitudinal data].

BACKGROUND: Data on the treatment of hip fractures in acute care settings have been collected in a report card system for quality assurance in Germany since the beginning of the 1990s. However, there are no data on the long-term outcome and long-term quality of care. MATERIAL AND METHOD: In a retrospective study, data on 1393 patients from 1999 were collected from different sources: from the department of quality assurance at the medical association of Westfalia-Lippe, the Statutory Health Insurance Funds (AOK), and the Medical Review Board of the Statutory Health Insurance Funds (Medizinischer Dienst der Krankenkasse, MDK). Statistical analyses were performed by the Center for Clinical Studies of the University of Düsseldorf. RESULTS: Uni- and multivariate analyses reveal the following prognostic parameters for survival after hip fracture: sex, age, nursing care dependency, living in a nursing home, risk stratification according to ASA, and postoperative complications. Timing of the operation had no affect on survival. CONCLUSIONS: Prognostic factors for the outcome after hip fracture can only be obtained by analyzing data from the hospital stay and the post-hospital setting as well. Chances of survival can be significantly improved by rehabilitative care.

Age Distribution↗

PubMed2006

Longitudinal data on telomere length in leukocytes from newborn baboons support a marked drop in stem cell turnover around 1 year of age.

Stem cells of various tissues are typically defined as multipotent cells with 'self-renewal' properties. Despite the increasing interest in stem cells, surprisingly little is known about the number of times stem cells can or do divide over a lifetime. Based on telomere-length measurements of hematopoietic cells, we previously proposed that the self-renewal capacity of hematopoietic stem cells is limited by progressive telomere attrition and that such cells divide very rapidly during the first year of life. Recent studies of patients with aplastic anemia resulting from inherited mutations in telomerase genes support the notion that the replicative potential of hematopoietic stem cells is directly related to telomere length, which is indirectly related to telomerase levels. To revisit conclusions about stem cell turnover based on cross-sectional studies of telomere length, we performed a longitudinal study of telomere length in leukocytes from newborn baboons. All four individual animals studied showed a rapid decline in telomere length (approximately 2-3 kb) in granulocytes and lymphocytes in the first year after birth. After 50-70 weeks the telomere length appeared to stabilize in all cell types. These observations suggest that hematopoietic stem cells, after an initial phase of rapid expansion, switch at around 1 year of age to a different functional mode characterized by a markedly decreased turnover rate.

Aging↗

PubMed2001

Use of repeated measure linear modeling to analyze longitudinal data from experimental parasite infections.

Here the use of repeated measure linear modeling to analyze experimental infections is demonstrated. This method of analysis makes full use of serial measurements on the same host throughout the course of an infection while taking into account correlations between measures within the same host. As an example, repeated measure linear modeling is used to analyze worm output from an experimental infection of Strongyloides ratti, a nematode parasite of rats. This analysis allows differences in the temporal dynamics of infection of two lines of S. ratti to be dissected.

Animals↗

PubMed2003

Estimating the accuracy of psychological scales using longitudinal data.

This article presents a method for estimating the accuracy of psychological screening scales using receiver operating characteristic curves and associated statistics. Screening scales are typically semicontinuous within a known range with distributions that are nearly symmetric when the target condition is present and highly skewed when the condition is absent. We model screening scale outcomes using truncated normal distributions that accommodate these different distributional shapes and use subject-specific random effects to adjust for multiple assessments within individuals. Using the proposed model, we estimate the accuracy of the Symptom Checklist as a measure of major depression from a repeatedly screened sample of patients.

Antidepressive Agents↗

PubMed2002

Patterns of depressed mood across the menopausal transition: approaches to studying patterns in longitudinal data.

To date many researchers have focused on depression as a discrete episode, attempting to relate its occurrence to a transition in menopausal stage or other factors that might account for its occurrence. Characterizing change over time requires consideration of pattern or trajectory, not merely discrete events. The purposes of this paper are to: 1) to explore methods for intraindividual and interindividual (group) analysis of patterns of depressed mood among midlife women 2) to identify challenges for analytic strategies for understanding depressed mood as it is experienced by midlife women, with special concern for its relationship to the menopausal transition. Data from the Seattle Midlife Women's Health Study were used to illustrate approaches to intraindividual and interindividual analysis of patterns of depressed mood. For most women, menopausal transition was not a time when there was a new episode of depression. Instead, a minority of women showed evidence of becoming depressed once the transition had begun. The most prevalent pattern was that of non-depressed mood across the years of the menopausal transition. Association of several factors with a pattern of depressed mood included life stressors, perceived poor health, and vasomotor symptoms.

Cluster Analysis↗

PubMed2003

Genetic analysis of phenotypes derived from longitudinal data: Presentation Group 1 of Genetic Analysis Workshop 13.

The participants of Presentation Group 1 used the GAW13 data to derive new phenotypes, which were then analyzed for linkage and, in one case, for association to the genetic markers. Since the trait measurements ranged over longer time periods, the participants looked at the time dependence of particular traits in addition to the trait itself. The phenotypes analyzed with the Framingham data can be roughly divided into 1) body weight-related traits, which also include a type 2 diabetes progression trait, and 2) traits related to systolic blood pressure. Both trait classes are associated with metabolic syndrome. For traits related to body weight, linkage was consistently identified by at least two participating groups to genetic regions on chromosomes 4, 8, 11, and 18. For systolic blood pressure, or its derivatives, at least two groups obtained linkage for regions on chromosomes 4, 6, 8, 11, 14, 16, and 19. Five of the 13 participating groups focused on the simulated data. Due to the rather sparse grid of microsatellite markers, an association analysis for several traits was not successful. Linkage analysis of hypertension and body mass index using LODs and heterogeneity LODs (HLODs) had low power. For the glucose phenotype, a combination of random coefficient regression models and variance component linkage analysis turned out to be strikingly powerful in the identification of a trait locus simulated on chromosome 5. Haseman-Elston regression methods, applied to the same phenotype, had low power, but the above-mentioned chromosome 5 locus was not included in this analysis.

Cardiovascular Diseases↗

PubMed1996

Reading disabilities with and without behaviour problems at 7-8 years: prediction from longitudinal data from infancy to 6 years.

Seven-year-old children with reading disabilities (RD-only), behaviour problems (BP-only), both conditions (RD-BP) and neither condition (Comparison) were compared on indices including temperament and behaviour, gathered in five periods between infancy and 6 years of age. The RD-BP group differed clearly from the RD-only group from infancy onwards. This comorbid group was similar to the BP-only group, while the RD-only group was similar to the Comparison group, until school age. The gender composition of the two RD groups differed, and the RD-BP boys showed the most problematic characteristics. The findings indicate different developmental pathways for "pure' RD children and those with comorbid BPs.

Attention Deficit Disorder with Hyperactivity↗

PubMed2002

Job mobility, its determinants, and its effects: longitudinal data from the Maastricht Cohort Study.

This prospective study of 12,140 employees examined the effects of work characteristics and situational, psychological, and health aspects on job mobility. Before job change, the mobility group reported significantly more conflicts with the supervisor, higher physical and emotional strain, higher degree of job insecurity, lower job satisfaction, and lower degree of commitment compared with employees who did not change jobs. After job change, the mobility group reported improved autonomy, task diversity, decreased occurrence of conflicts with the supervisor, decreased physical and emotional strain, and improved training possibilities and job security than before the change. Changing jobs had a positive effect on employees with respect to job perception and job satisfaction and led to reduced fatigue and need for recovery.

Adolescent↗

PubMed1986

Quantitative assessment of malaria morbidity based on longitudinal data in 10 Indian villages.

House-to-house visits were made at weekly intervals to investigate malaria morbidity. The survey covered 7337 individuals in 10 villages in Jhansi District, Uttar Pradesh. Incidence rates of 252 spells of sickness from fever and six symptomatic cases of malaria per 1000 population were recorded. The incidence rates of unhealthy periods due to fever, of people sick and of spells of sickness per person were significantly higher in males. Morbidity from fever was highest in the 15-24 year age group in males and in the 10-14 year age group in females. The rates for malaria did not show any correlation with age. Morbidity rates were relatively higher from July to October, peaking in September. The annual slide positivity rate was 2.4%. Plasmodium vivax and P. falciparum were the only species observed in the area, with the former more prevalent.

Adolescent↗