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Only one genome scan to date has attempted to make use of the longitudinal data available in the Framingham Heart Study, and this attempt yielded evidence of linkage to a gene for mean systolic blood pressure. We show how the additional information available in these longitudinal data can be utilized to examine linkages for not only mean systolic blood pressure (SBP), but also for its trend with age and its variability. Prior to linkage analysis, individuals treated for hypertension were adjusted to account for right-censoring of SBP. Regressions on age were fitted to obtain orthogonal measures of slope, curvature, and residual variance of SBP that were then used as dependent variables in the model-free linkage program SIBPAL. We included mean age, gender, and cohort as covariates in the analysis. To improve power, sibling pairs were weighted for informativity using weights derived from both the marker and trait. The most significant results from our analyses were found on chromosomes 12, 15, and 17 for mean SBP, and chromosome 20 for both SBP slope and curvature.
BACKGROUND: Little longitudinal data are available on the general physical, psychological, and social problems experienced as a result of laryngectomy or on the preoperative status of patients in regard to these aspects. In particular, prospective longitudinal data gathered from the same group of subjects over time and examining a variety of such outcomes is rare. This descriptive study addresses these issues. METHODS: The study investigates the progress of a group of 34 laryngectomees from the preoperative stage up to 6 months after surgery. Medical complications, communication, swallowing, diet, physical, and psychosocial adjustment were measured using both the Short-Form Health Survey (SF-36) and original outcome tools. RESULTS: A large percentage of subjects demonstrated significant and persistent communication and swallowing problems throughout the period studied. Low preoperative and postoperative scores on the SF-36 demonstrate that this group had a poorer state of general health in many respects than those with serious medical conditions previously documented. CONCLUSIONS: The results suggest that communication and swallowing difficulties persist for many laryngectomees up to 6 months after surgery and still require further investigation. Poor preoperative and postoperative general health scores indicate that this group may require more long-term social support than is currently being offered to adjust to the laryngectomy. Copyright 2000 John Wiley & Sons, Inc. Head Neck 23: 16-24, 2001.
BACKGROUND: Little longitudinal data are available on the general physical, psychological, and social problems experienced as a result of laryngectomy or on the preoperative status of patients in regard to these aspects. In particular, prospective longitudinal data gathered from the same group of subjects over time and examining a variety of such outcomes is rare. This descriptive study addresses these issues. METHODS: The study investigates the progress of a group of 34 laryngectomees from the preoperative stage up to 6 months after surgery. Medical complications, communication, swallowing, diet, physical, and psychosocial adjustment were measured using both the Short-Form Health Survey (SF-36) and original outcome tools. RESULTS: A large percentage of subjects demonstrated significant and persistent communication and swallowing problems throughout the period studied. Low preoperative and postoperative scores on the SF-36 demonstrate that this group had a poorer state of general health in many respects than those with serious medical conditions previously documented. CONCLUSIONS: The results suggest that communication and swallowing difficulties persist for many laryngectomees up to 6 months after surgery and still require further investigation. Poor preoperative and postoperative general health scores indicate that this group may require more long-term social support than is currently being offered to adjust to the laryngectomy.
In cancer drug development, demonstrated anticancer activity in animal models is an important step to bring a promising compound to clinic. Proper design and analysis of experiments using laboratory animals have received increasing attention recently. These experiments involve informatively censored longitudinal data with small samples. The problem is further complicated because of order constraints due to the intrinsic growth of control tumors without treatment. This article proposes a Bayesian hierarchical model to analyze informatively censored longitudinal data while accounting for the parameter constraints and providing valid small sample inference. We adopt a noniterative sampling approach, the inverse Bayes formulae (IBF) sampler, to generate independent posterior samples, which avoids convergence problems associated with Markov chain Monte-Carlo methods. To effectively deal with the restricted parameter problem, we use a linear transformation to simplify the constraints and exploit the IBF method to generate random samples from truncated multivariate normal distributions. Because diffuse priors are used, the posterior modes approximate the maximum likelihood estimates well, and the hierarchical model can be considered as an extended mixed-effects model. A real xenograft experiment on a new treatment is analyzed by using the proposed method.
We extend the marginalized transition model of Heagerty to accommodate non-ignorable monotone drop-out. Using a selection model, weakly identified drop-out parameters are held constant and their effects evaluated through sensitivity analysis. For data missing at random (MAR), efficiency of inverse probability of censoring weighted generalized estimating equations (IPCW-GEE) is as low as 40 per cent compared to a likelihood-based marginalized transition model (MTM) with comparable modelling burden. MTM and IPCW-GEE regression parameters both display misspecification bias for MAR and non-ignorable missing data, and both reduce bias noticeably by improving model fit.
Recent protocols for standardized knee radiography, which attempts to image the knee with reproducible, parallel alignment of the medial tibial plateau and radiograph beam, possess many theoretic advantages. As a group, they permit measurement of tibiofemoral joint space width with remarkable precision--the sine qua non of sensitive detection of change. However, only limited longitudinal data are available in peer-reviewed publications to permit a direct evaluation of the suitability of these protocols for use in multicenter clinical trials and studies of biomarkers of osteoarthritis (OA) progression. Longitudinal data from several National Institutes of Health-supported studies of OA progression, as reflected in radiographs acquired with high levels of standardization for radioanatomic positioning of the knee, should be available in the next several years. Alternatively, data from the placebo groups of several industry-supported phase III trials of purported disease-modifying OA drugs, which were terminated prematurely because of adverse events or lack of efficacy, may be made available for rapid analysis regarding the performance of current standardization protocols with respect to their sensitivity to disease progression.
Reciprocal effects models of longitudinal data show that academic self-concept is both a cause and an effect of achievement. In this study this model was extended to juxtapose self-concept with academic interest. Based on longitudinal data from 2 nationally representative samples of German 7th-grade students (Study 1: N = 5,649, M age = 13.4; Study 2: N = 2,264, M age = 13.7 years), prior self-concept significantly affected subsequent math interest, school grades, and standardized test scores, whereas prior math interest had only a small effect on subsequent math self-concept. Despite stereotypic gender differences in means, linkages relating these constructs were invariant over gender. These results demonstrate the positive effects of academic self-concept on a variety of academic outcomes and integrate self-concept with the developmental motivation literature.
OBJECTIVE: To present a new model for analyzing longitudinal data. The trilinear model is superior to the commonly used linear model that includes the flawed assumption that decline is uniform throughout the course of disease--an assumption that does not correspond to clinical observations. DESIGN: A longitudinal cohort sample was used to compare the linear and trilinear models. Simulated longitudinal data were generated to assess classification errors with the trilinear model. SUBJECTS AND SETTING: The subjects were 80 patients with Alzheimer's disease tested in a hospital out-patient clinic. METHODS: The trilinear model describes Alzheimer's disease as proceeding through three periods: An initial period of stability before detectable decline, a period of decline, and a final period of stability during which there is no further detectable decline. A program for the Apple Macintosh computer is available at no charge to apply the model to data. FINDINGS: The analyses indicated that the trilinear model provides a better reflection of decline in Alzheimer's disease than does the linear model. This advantage is present whether the periods of stability reflect a "true" lack of decline or insensitivity of a measurement instrument. CONCLUSIONS: The trilinear model provides not only a more accurate estimate of the average rate of change, but also (when possible) estimates of the point at which decline begins and ends. Also, more detailed comparisons of tests could be made by using the trilinear parameters. The trilinear model would benefit researchers engaged in longitudinal research of progressive disorders.
Cross-sectional data have previously indicated poor growth and development among adolescent girls in Mali. These data have shown that Malian girls are shorter and lighter than their United States female counterparts. Many studies suggest that this evidence of poor growth and development is due to a combination of poor nutrient intake, high-energy expenditure, and poor access to health care. At adolescence, individuals rarely follow a standard pattern of growth due to different biological timetables and expressions of pubertal growth. By examining velocity of growth, researchers can recognize developmental patterns such as compensatory gain. This study examines the growth rates of Malian girls over a 6-month period. Anthropometric data were collected from a total of 1,045 adolescent girls ages 10-17 years. Height and weights were collected twice from the Segou Coura community in the town of Segou and from the Dioro Arrondissement in 1997. From these data, mixed longitudinal analyses were conducted. Both the height and weight velocity data showed patterns of delayed growth rates when compared with American girls. Although Malian girls are similar to American girls in that they tend to reach their peak height velocity at age 12, the Malian girls demonstrate a longer growth spurt than the American girls. This evidence of greater height velocity may be an indication of compensatory growth, or compensatory gain, and is partially supported from cross-sectional data. While these Malian data do not show much evidence that certain stressors are relieved during adolescence, only more extensive longitudinal data can more fairly examine the issue.
BACKGROUND: Health care funding levels differ significantly across geographic regions, but there is little correlation between regional funding levels and outcomes of elderly Medicare beneficiaries. Our goal was to determine whether this relationship holds true in a non-Medicare population cared for in a large integrated health care system with a capitated budget allocation system. METHODS: We explored the association between health care funding and risk-adjusted mortality in the 22 Veterans Affairs (VA) geographic Networks over a six-year time period. Allocations to Networks were adjusted for illness burden using Diagnostic Cost Groups. To test the association between funding and risk-adjusted three-year mortality, we ran logistic regressions with single-year patient cohorts, as well as hierarchical regressions on a six year longitudinal data set, clustering on VA Network. RESULTS: A 1000 dollar increase in funding per unit of patient illness burden was associated with a 2-8% reduction in three-year mortality in cross sectional regressions. However, in longitudinal hierarchical regressions clustering on Network, the significant effect of funding level was eliminated. CONCLUSIONS: When longitudinal data are used, the significant cross sectional effect of funding levels on mortality disappear. Thus, the factors driving differences in mortality are Network effects, although part of the Network effect may be due to past levels of funding. Our results provide a caution for cross sectional examinations of the association between regional health care funding levels and health outcomes.
A clinicopathological study was performed on 114 patients (46 male/68 female, median age 67 years) with the diagnosis of agnogenic myeloid metaplasia (AMM) respectively primary osteo-myelofibrosis which was not preceded by any other or allied subtype of chronic myeloproliferative disorders. On admission patients revealed a striking variability of laboratory data as well as different histopathological features of initial bone marrow biopsies. For this reason discrimination was done into two groups based on bone marrow findings: group I patients (n = 46, 19 male/27 female) showed a hypercellular marrow without or only borderline (n = 24) to slight (n = 22) reticulin fibrosis and group II cases (n = 68, 27 male/41 female) displayed coarse bundles of collagen fibres (n = 18) frequently accompanied by osteosclerosis (n = 50). Statistical analysis of the corresponding initial hematological findings resulted in significant differences. These differences concerned also the complications occurring during the lengthy course of disease, which included a higher incidence of pancytopenia and severe marrow failure with hemorrhage and blast crisis in group II patients. However, overall survival time was not different in both groups. This may be related to the similarity of age distribution (64 resp. 65 years) and its significant association with arteriosclerotic vascular lesions. Consequently acute myocardial infarction and congestive heart failure were frequent causes of death in addition to infections due to marrow failure and blast crisis. Repeated bone marrow biopsies in 24 patients revealed an insidious transition from hypercellular lesions (group I) into advanced fibro-osteosclerotic changes (group II) concurring with laboratory data. Therefore our discrimination into two groups of patients represents variable stages or static histological and corresponding hematologic features in the evolution of a dynamic disease process in AMM.
BACKGROUND: Both social class and unemployment have been shown in many studies to be related to ill health. Recent work in social epidemiology has demonstrated the importance of examining the accumulation of disadvantage over the life course. This paper therefore uses a large longitudinal data set to examine the accumulation of both disadvantaged class and unemployment over a 20-year period in a representative sample of the male working population of England and Wales. METHODS: Logistic regression. RESULTS: Both membership of semi- or unskilled social class and unemployment in 1971 were related to limiting long-term illness (LLTI) in 1991 independently of each other, and of subsequent social class and unemployment. Any occurrence of disadvantaged social class or of unemployment added significantly to the risk of LLTI. A labour market disadvantage score comprising the number of occasions on which a study member had been either in a disadvantaged social class or unemployed showed a clear and graded relationship to illness, with odds of 4 to 1 in the worst-scoring group. CONCLUSION: The experiences of disadvantaged social class or unemployment at any time during this period contributed independently to an increased risk of chronic limiting illness up to 20 years later in the life course. Whereas improvements in social conditions at any one time will lessen the long-term combined impact of accumulated labour market disadvantage on health, it may not prove easy to obtain short term improvements in health inequality.
This article examines the psychological impact of participating in sigmoidoscopy screening for colorectal cancer prevention. The 1st study examined psychological well-being at 3 months, in relation to screening outcome, in 4,153 individuals. The 2nd study used longitudinal data to examine changes in psychological functioning from before to after screening in relation both to screening outcome and baseline indicators of vulnerability. There were few psychological differences between those who had received negative results or had polyps detected. These findings were confirmed in the longitudinal study, which also found no evidence for vulnerability to adverse effects among those who were initially most anxious or who perceived their risk of cancer to be higher. The longitudinal data suggested that screening might produce transient positive effects.
OBJECTIVES: This study estimates the consequences of older husbands' involuntary job loss for their wives' mental health. METHODS: Using longitudinal data from the 1992, 1994, and 1996 waves of the Health and Retirement Study, multivariate regression models were estimated to measure the impact of older husbands' involuntary job loss on wives' mental health. We created two longitudinal data sets of two waves each to use in our analysis. The first data set, or period, combined Waves 1 and 2 of the Health and Retirement Study and described the 1992-1994 experience of spouse pairs in our sample. It included the wives of 55 husbands who experienced involuntary job loss between these survey dates and a comparison group of wives of 730 continuously employed husbands. The second data set described the 1994-1996 experience of couples. In particular, it included the wives of an additional 38 husbands who were displaced from their jobs between Waves 2 and 3, and a comparison group of wives of 425 husbands who were continuously employed from 1994 to 1996. RESULTS: Husbands' involuntary job loss did not have a statistically significant effect on wives' mental health. We found no evidence that changes in husbands' depressive symptoms modified the effect of his job loss on wives' mental health. In the first period only, the effect of husbands' job loss on wives' mental health was more pronounced for wives who were more financially satisfied at baseline. DISCUSSION: There is limited evidence among this cohort that husbands' job loss increases wives' subsequent depressive symptoms. However, the effect of husbands' job loss on wives' mental health appears to be magnified when wives report being financially satisfied pre-job loss. This suggests that, for subgroups of older couples, mental health services specifically targeted at displaced men should also be made available to wives.
The purpose of this study was to develop a model that predicts the outcome of supervised exercise for intermittent claudication. The authors present an example of the use of autoregressive logistic regression for modeling observed longitudinal data. Data were collected from 329 participants in a six-month exercise program. The levels of the polytomous outcome variable correspond to states they defined in a Markov decision model comparing treatment strategies for intermittent claudication. Autoregressive logistic regression can be used to fit multistate transition models to observed longitudinal data with standard statistical software. The technique allows exploration of alternative assumptions about the dependence in the outcome series and provides transition probabilities for different covariate patterns. Of the alternatives examined, a Markov model including two preceding responses, time, age, ankle brachial index, and duration of disease best described the data.
Total cholesterol (TC) and HDL-cholesterol (HDL-C) have been studied in dialysis patients, but a systematic study of apolipoprotein (apo) A-I, apo B, and the anti-atherogenic risk ratio, apo A-I/apo B, over time has not been done. We report lipid and apo values over 12-14 months in 55 hemodialysis (HD) and 40 continuous ambulatory peritoneal dialysis (CAPD) patients. For HD patients, mean TC fell, but not significantly, and HDL-C and TC/HDL-C, an atherogenic risk ratio, did not change over time. Apo A-I/apo B correlated with months on HD (r = 0.30, p less than 0.04) and rose significantly (p less than 0.005) during the study period. Paired t-test analysis by race, gender, and diabetes showed that in nondiabetics, apo A-I rose, apo B fell (p less than 0.05), and apo A-I/apo B improved (p less than 0.002). Similar trends were seen in all subgroups except for diabetics. For CAPD patients, total months of treatment correlated with TC/HDL-C (r = 0.46, p less than 0.05) and with HDL-C (r = -0.53, p less than 0.02), but paired t-test analysis of longitudinal data showed no significant changes in TC, HDL-C, apo A-I, apo B, TC/HDL-C, or apo A-I/apo B. The lipoprotein patterns of all patients who died were not significantly different from those of the surviving patients. Our longitudinal data reveal that lipids, apolipoproteins, and risk ratios remain stable over time on HD and CAPD. In fact, the anti-atherogenic index of apo A-I/apo B improved in HD patients, especially in nondiabetics.
PURPOSE: Longitudinal data have provided evidence on factors that increase the risk of incidence of functional limitations. However, little insight exists in course types of functional limitations other than simple incidence or recovery. METHODS: This contribution examines the variety of course types across the first three cycles of the Longitudinal Aging Study Amsterdam (n = 3107, initial ages 55 - 85 years, 6-year period covered). Using cluster analysis, course types were determined among both the survivors and the deceased. Multinomial analyses were performed to determine the predictive ability of baseline physical and mental chronic conditions for each course type. RESULTS: Eight course types were distinguished: (1) stable not limited (53%) (2) stable mild (8%) (3) stable severe (3%) (4) gradual increase (4%) (5) delayed increase (5%) (6) not limited, died t3 (8%) (7) increase t1-t2, died t3 (4%) (8) died t2 (15%). Socio-demographic and chronic conditions differentially predicted the course types. Arthritis was predictive mainly of course types not ending in death, cancer of course types ending in death. The other physical and mental conditions were predictive of both. CONCLUSION: These longitudinal data show the usefulness of distinguishing between course types of functional limitations beyond incidence and recovery.