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At least 883 records · Page 49Linked to original sources
PubMed2006

Measurement of lumbar lordosis: inter-rater reliability, minimum detectable change and longitudinal variation.

STUDY DESIGN: Repeated measures design to examine reliability and longitudinal variation of lumbar lordosis measurement. OBJECTIVES: To determine the interrater reliability, minimum detectable change (MDC) and longitudinal variation of the Cobb method for measuring lumbar lordosis using standardized rules. SUMMARY OF BACKGROUND DATA: The reliability of the 4-line Cobb method for measuring lumbar lordosis was not examined when standardized rules were instituted for drawing the lines. METHODS: A random sample of participants was selected from the Pittsburgh clinic of the multicenter Study of Osteoporotic Fractures for radiographic measurement of lumbar lordosis reliability (n=48) and stability (n=109). A standardized version of the 4-line Cobb method was used for all measurements of lordosis. The Intraclass Correlation Coefficient (ICC) was used to calculate interrater reliability for lordosis and to measure the stability of this measure over an approximate 2-year-time period. The standard error of measurement and MDC were calculated for lordosis measurement based on the ICC value. RESULTS: The interrater reliability coefficient for lumbar lordosis was in the excellent range (ICC=0.98; 95% CI: 0.95, 0.99). The MDC based on measurements between raters was 3.90 degrees. The ICC value for the stability, or reliability from time 1 to time 2, of lordosis measurement over time was 0.81 (95% CI: 0.74, 0.87). CONCLUSION: This study demonstrates that the 4-line Cobb method can be a highly reliable and precise method for measuring lumbar lordosis if standardized procedures are used. The Cobb method has an MDC that is appropriate for clinical use. Also, there is minimal longitudinal variation in lordosis measurements over a 2-year period.

Aged↗
PubMed2004

Bowel function and bother after treatment for early stage prostate cancer: a longitudinal quality of life analysis from CaPSURE.

PURPOSE: We measured bowel function and bowel bother longitudinally the first 2 years after treatment for early stage prostate cancer. MATERIALS AND METHODS: We studied bowel function and bother in 1,584 men recently diagnosed with early stage prostate cancer and followed for 2 years after radical prostatectomy, external beam radiation or brachytherapy. Principal outcomes were assessed with the UCLA Prostate Cancer Index, a validated instrument that includes these 2 domains. Multivariate analyses were conducted to ascertain significant predictors of bowel function and bother. Subjects were drawn from Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE, TAP Pharmaceutical Products, Inc., Lake Forest, Illinois), a national, longitudinal registry of men with prostate cancer. RESULTS: Men treated with external beam radiation or brachytherapy suffered worse bowel function and were more bothered by it than men treated surgically. After an initial period of posttreatment impairment, all 3 groups demonstrated improvement with time in both domains, although bowel bother persisted longer in men treated with external beam radiation. Surgery patients reached a steady state by 3 months, while those treated with external beam radiation or brachytherapy continued to improve for more than a year after treatment. Older men were more bothered by bowel dysfunction than younger men. Ethnicity, comorbidity and education did not affect either bowel function or bother. CONCLUSIONS: Patients undergoing surgery, external beam radiation or brachytherapy have different longitudinal profiles of bowel function and bother during the first 2 years after treatment. Bowel function and bother are worse after external beam radiation but they are also impaired after brachytherapy. Men choosing surgery experience transient impairment in the bowel domains. This information may be useful to patients making treatment decisions for early stage prostate cancer.

Adenocarcinoma↗
PubMedDate not supplied

Longitudinal modifications of the MELD score have prognostic meaning in patients with liver cirrhosis.

BACKGROUND: The Model for End-Stage Liver Disease (MELD) score is an important and well established tool for assessing prognosis in patients with liver cirrhosis. It has been suggested that the longitudinal evaluation of the MELD score may reflect the progression of liver failure more reliably and therefore be more useful in prognostic assessment. AIM: To assess the prognostic meaning of MELD score modifications in a cohort of cirrhotic patients in whom clinical and biochemical workup was carried out at least twice during a minimum interval of 30 days. METHODS: Forty-six cirrhotic patients were longitudinally evaluated for a median follow-up of 365 days. After initial assessment, all the patients had at least one clinical and biochemical reevaluation during follow-up, which was performed no less than 1 month after initial evaluation. MELD was calculated at entry and at second evaluation. DeltaMELD was calculated as MELD at second evaluation minus MELD at entry. DeltaMELD/time was calculated as DeltaMELD divided by time elapsed between initial assessment and second evaluation expressed in months. RESULTS: During follow-up, 13 patients died (28%). The median interval between clinical evaluations was 120 days. MELD scores at entry (13 +/- 4 vs 16 +/- 6, P = 0.0516) and DeltaMELD (0 +/- 4 vs 4 +/- 2, P = 0.0028) were significantly different between patients who died and those who survived during the 1-year follow-up. All the patients who died during follow-up showed an increase of at least 1 unit in DeltaMELD/time (sensitivity = 100%), and all the patients who survived showed a decrease of more than 1 unit in DeltaMELD/time (specificity = 100%). CONCLUSIONS: Longitudinal evaluation of the MELD score provides important prognostic information that seems to complete the prognostic definition provided by "static" MELD. Prospective studies in larger series are needed to validate the prognostic use of MELD modifications over time.

Adult↗
PubMed2006

The utility of extended longitudinal profiles in predicting future health care expenditures.

BACKGROUND: Health care spending is highly concentrated. Prediction models that accurately identify the characteristics of individuals most likely to incur high levels of health expenditures in a subsequent year are important analytical and statistical tools. OBJECTIVES: This study examined the capacity of alternative models to predict the likelihood of incurring high levels of medical expenditures in a subsequent year. This effort also evaluated the utility of an additional year of longitudinal information. SUBJECTS: A nationally representative sample from the Medical Expenditure Panel Survey (MEPS). METHODS: The MEPS longitudinal data are used to examine the persistence of high expenditures during a 2-year period. With the unique linkage of the MEPS to the National Health Interview Survey, the utility of an additional year of data also was examined. Resultant models were evaluated in terms of sensitivity, specificity, and predictive capacity. RESULTS: Only modest marginal gains in discrimination capacity were realized from the use of extended longitudinal profiles from the National Health Interview Survey, relative to information on prior year characteristics. CONCLUSIONS: Our results highlight the continuing concentration of health care expenditures during the period 1996 to 2002 and reveal some attenuation in magnitude in the tail of this distribution over time. Further, our results provide evidence of the utility of probabilistic models as prediction tools to identify individuals likely to incur high levels of expenditures in future years. Predictive capacity does not suffer when restricted to a single year of prior information.

Adolescent↗
PubMed2006

Transforming the SF-36 to account for death in longitudinal studies with three-year follow-up.

BACKGROUND: Analyses of longitudinal health-related quality of life data often exclude participants who die, which limits the generalizability of the results. Methods to incorporate death as a valid score in the Medical Outcomes Study Short-Form (SF-36) have been suggested but need to be evaluated in other populations. OBJECTIVES: We sought to apply a method of transforming the SF-36 Physical Component Score (PCS) to include death. A transformation to estimate the probability of being "healthy" in 3 years, based on the current PCS value, will be developed and validated. SUBJECTS: Women in the Australian Longitudinal Study on Women's Health (ALSWH), ages 70-75 years at Survey 1 in 1996 (n = 12,432), were followed-up at 3 yearly intervals for 6 years. RESULTS: The transformation derived from the ALSWH data provides evidence that the methodology for transforming the PCS to account for deaths is sound. The 3-year equation provided good estimates of the probability of being healthy in 3 years and the method allowed deaths to be included in an analysis of changes in health over time. CONCLUSIONS: For longitudinal studies involving the SF-36 in which subjects have died, we support the recommendation that both the PCS and its transformed value which includes deaths should be analyzed to examine the influence of deaths on the study conclusions. Using study data to derive empirical parameters for the transformations may be appropriate for studies with follow-up intervals of other lengths.

Aged↗
PubMedDate not supplied

Longitudinal course of depressive symptomatology after a cardiac event: effects of gender and cardiac rehabilitation.

OBJECTIVE: Recent research has linked depression to cardiac mortality, and shown a high burden of persistent depressive symptomatology among cardiac patients. The objective of this study was to longitudinally examine the prevalence and course of depressive symptomatology among women and men for 1 year after a cardiac event, and the effect of cardiac rehabilitation (CR) on this trajectory. METHODS: Nine hundred thirteen unstable angina (UA) and myocardial infarction patients from 12 coronary care units were recruited, and follow-up data were collected at 6 and 12 months. Measures included CR participation, medication usage, and the Beck Depression Inventory (BDI). The longitudinal analysis was conducted using SAS PROC MIXED. RESULTS: At baseline there were 277 (31.3%) participants with elevated depressive symptomatology (BDI > or = 10), 131 (25.2%) at 6 months, and 107 (21.7%) at 1 year. Overall, approximately 5% were taking an antidepressant medication, and 20% attended CR over their year of recovery. Participants with greater depressive symptomatology participated in significantly fewer CR exercise sessions (r = -0.19, p = .02), and minimal psychosocial interventions were offered. The longitudinal analysis revealed that all participants experienced reduced depressive symptomatology over their year of recovery (p = .04), and younger, UA participants with lower family income fared worst (ps < 0.001). CR did not have an effect on depressive symptomatology over time, but women who attended CR were significantly more depressed than men (p = .01). CONCLUSION: Depressed cardiac patients are undertreated and their symptomatology persists for up to 6 months. CR programs require greater resources to ensure that depressed participants adhere to exercise regimens, and are screened and treated for their elevated symptomatology.

Age Factors↗
PubMed2004

Quality of life: a longitudinal analysis of correlates of morale in old age.

This paper examines recurrent continuous morale in old age within a statistical modelling paradigm. The Anglicised Philadelphia Geriatric Centre Morale Scale was used as a small component of a major longitudinal study of old age in rural North Wales, U.K. The literature review and cross-sectional analysis of morale in old age is published elsewhere. This paper deals with the aspect of the longitudinal analysis of morale in old age. The proposed statistical modelling relates recurrent morale to a set of explanatory variables that includes subjective as well as objective measures. In order to assess the degree to which explanatory variables influence morale, an adequate statistical model must handle the possibility that substantial variation between respondents will be due to unmeasured and potentially unmeasurable variables (residual heterogeneity), multicollinearity, and past behaviour effect. These applications are illustrated using morale in old age from the North Wales Longitudinal Study Old Age. The results suggested a strong presence of heterogeneity effect, i.e., current levels of morale appear to be individual specific and independent of its previous levels.

Aged↗
PubMed2005

Beat-to-beat estimate of fetal cardiac time intervals using magnetocardiography: longitudinal charts of normality ranges and individual trends.

BACKGROUND: Fetal magnetocardiography (fMCG) records fetal cardiac electro-physiological activity during the second half of gestation. We aimed at assessing normality values, related variability, and trends of fetal cardiac time intervals (fCTI) evaluated longitudinally from beat-to-beat fMCG analysis in uncomplicated pregnancies. MATERIALS AND METHODS: The fMCG were recorded with multi-channel system in shielded room. FCTI were estimated on more than 2600 fetal cardiac cycles from 51 fMCG data sets of uncomplicated pregnancies. Independent component analysis (ICA) allowed reconstructing reliable fetal signals for beat-to-beat identification of fCTI (RR, P wave, PQ, PR, QT, QTc, QRS, ST, and T wave); intra-individual variability analysis and trends were calculated; reference longitudinal charts accounted for intra- and inter-individual variations and were compared with figures estimated on averaged signals. RESULTS: For each data set, fCTI were calculated beat-to-beat on rhythm strips of more than 50 beats (95% overall detection rate). FCTI values, variability, and trends were in good agreement with available reference figures; intervals related to P and T waves were, respectively, underestimated and overestimated with respect to those estimated on averaged signals or obtained by other research groups. Errors were reduced and individual trends could be drawn. CONCLUSIONS: ICA permitted the reconstruction of reliable time course of fetal cardiac signals and the beat-to-beat calculation of time intervals, and normality ranges, with smaller errors with respect to previous studies. The retrieval of fetal traces with clear morphology and the longitudinal character of the study allowed estimating individual trends and beat-to-beat characterization, impossible with cross-sectional studies on averaged beats.

Adult↗
PubMed2000

Modeling longitudinal data with ordinal response by varying coefficients.

This paper presents a smooth regression model for ordinal data with longitudinal dependence structure. A marginal model with cumulative logit link is applied to cope with the ordinal scale and the main and covariate effects in the model are allowed to vary with time. Local fitting is pursued and asymptotic properties of the estimates are discussed. In a second step, the longitudinal dependence of the observations is considered. Cumulative log odds ratios are fitted locally, which allows investigation of how the longitudinal dependence of the ordinal observations changes with time.

Biometry↗
PubMed2002

Mixed effects logistic regression models for multiple longitudinal binary functional limitation responses with informative drop-out and confounding by baseline outcomes.

In the context of analyzing multiple functional limitation responses collected longitudinally from the Longitudinal Study of Aging (LSOA), we investigate the heterogeneity of these outcomes with respect to their associations with previous functional status and other risk factors in the presence of informative drop-out and confounding by baseline outcomes. We accommodate the longitudinal nature of the multiple outcomes with a unique extension of the nested random effects logistic model with an autoregressive structure to include drop-out and baseline outcome components with shared random effects. Estimation of fixed effects and variance components is by maximum likelihood with numerical integration. This shared parameter selection model assumes that drop-out is conditionally independent of the multiple functional limitation outcomes given the underlying random effect representing an individual's trajectory of functional status across time. Whereas it is not possible to fully assess the adequacy of this assumption, we assess the robustness of this approach by varying the assumptions underlying the proposed model such as the random effects structure, the drop-out component, and omission of baseline functional outcomes as dependent variables in the model. Heterogeneity among the associations between each functional limitation outcome and a set of risk factors for functional limitation, such as previous functional limitation and physical activity, exists for the LSOA data of interest. Less heterogeneity is observed among the estimates of time-level random effects variance components that are allowed to vary across functional outcomes and time. We also note that. under an autoregressive structure, bias results from omitting the baseline outcome component linked to the follow-up outcome component by subject-level random effects.

Aged↗
PubMed2002

A latent autoregressive model for longitudinal binary data subject to informative missingness.

Longitudinal clinical trials often collect long sequences of binary data. Our application is a recent clinical trial in opiate addicts that examined the effect of a new treatment on repeated binary urine tests to assess opiate use over an extended follow-up. The dataset had two sources of missingness: dropout and intermittent missing observations. The primary endpoint of the study was comparing the marginal probability of a positive urine test over follow-up across treatment arms. We present a latent autoregressive model for longitudinal binary data subject to informative missingness. In this model, a Gaussian autoregressive process is shared between the binary response and missing-data processes, thereby inducing informative missingness. Our approach extends the work of others who have developed models that link the various processes through a shared random effect but do not allow for autocorrelation. We discuss parameter estimation using Monte Carlo EM and demonstrate through simulations that incorporating within-subject autocorrelation through a latent autoregressive process can be very important when longitudinal binary data is subject to informative missingness. We illustrate our new methodology using the opiate clinical trial data.

Algorithms↗
PubMed2002

Analysis of clustered and longitudinal binary data subject to response misclassification.

Misclassified clustered and longitudinal data arise in studies where the response indicates a condition identified through an imperfect diagnostic procedure. Examples include longitudinal studies that use an imperfect diagnostic test to assess whether or not an individual has been infected with a specific virus. This article presents methods to implement both population-averaged and cluster-specific analyses of such data when the misclassification rates are known. The methods exploit the fact that the class of generalized linear models enjoys a closure property in the case of misclassified responses. Data from longitudinal studies of infectious disease will illustrate the findings.

Biometry↗
PubMed2004

Latent pattern mixture models for informative intermittent missing data in longitudinal studies.

A frequently encountered problem in longitudinal studies is data that are missing due to missed visits or dropouts. In the statistical literature, interest has primarily focused on monotone missing data (dropout) with much less work on intermittent missing data in which a subject may return after one or more missed visits. Intermittent missing data have broader applicability that can include the frequent situation in which subjects do not have common sets of visit times or they visit at nonprescheduled times. In this article, we propose a latent pattern mixture model (LPMM), where the mixture patterns are formed from latent classes that link the longitudinal response and the missingness process. This allows us to handle arbitrary patterns of missing data embodied by subjects' visit process, and avoids the need to specify the mixture patterns a priori. One assumption of our model is that the missingness process is assumed to be conditionally independent of the longitudinal outcomes given the latent classes. We propose a noniterative approach to assess this key assumption. The LPMM is illustrated with a data set from a health service research study in which homeless people with mental illness were randomized to three different service packages and measures of homelessness were recorded at multiple time points. Our model suggests the presence of four latent classes linking subject visit patterns to homeless outcomes.

Biometry↗
PubMed1993

Cross-sectional and longitudinal study of the pituitary-thyroid axis in patients with thalassaemia major.

OBJECTIVE AND DESIGN: Thyroid dysfunction is known to occur frequently in thalassaemia major, but its prevalence and severity varies in different cohorts, and the long-term natural history is poorly described. We evaluated the pituitary/thyroid axis in thalassaemia major patients in a cross-sectional study and correlated abnormalities with indices of iron overload. Furthermore, the course of thyroid disease in thalassaemia major patients was assessed in a 15-year longitudinal study. PATIENTS AND MEASUREMENTS: Cross-sectional study: pituitary-thyroid axis function was examined in 37 patients (22 F, 15 M; aged 10-39 years, mean +/- SE = 21 +/- 1.4) out of a total of 43 who attended the Haematology and Endocrinology Clinics of Hadassah Hospital on a regular basis. The mean pretransfusion Hb level was 85 +/- 20 g/l, and all patients except one were treated with desferrioxamine (DF, mean +/- SE dose 20.2 +/- 2.6 mg/kg/day). Twenty-two had hypogonadotrophic hypogonadism (HH). Longitudinal study: 21 thalassaemia major patients were evaluated with TRH tests in 1976 and again in 1985. Fourteen of these and another eight were evaluated in both 1985 and 1991. RESULTS: Cross-sectional study: no patient had any clinical signs or symptoms of hypothyroidism; however, one had abnormally low T4, borderline low FT4 and normal T3 levels associated with an exaggerated TSH response to TRH consistent with mild hypothyroidism. This patient did not have a previous TRH test, but serial basal determinations over 7 years revealed a progressive decrease in thyroid function. Thirty-six patients had thyroid hormone levels within the normal range. Nine of these (24.3%) had only an exaggerated TSH response to TRH whereas seven others (19%) also had borderline elevated basal TSH levels. TSH response to TRH was not correlated with age, serum ferritin or liver function tests (ALT or GGT). Longitudinal study: mean TSH response to TRH decreased (P < 0.002), and mean T3 levels increased (P < 0.001) between 1975 and 1985. These findings are probably related to the initiation of DF treatment in 1981. During the last 6 years, four patients with previously normal TSH responses to TRH developed elevated peak TSH levels. Mean T3 concentrations decreased and TSH response to TRH increased significantly (P < 0.001 for both). CONCLUSIONS: (1) In this patient group the thyroid pituitary axis is less sensitive than the gonadal axis to iron-induced damage; only one out of 37 patients developed mild uncompensated hypothyroidism. (2) As opposed to the gonadal axis, the thyroid gland appears to fail before the central components of the axis. (3) Abnormal thyroid function may be reversible in the early stages. (4) Progression is variable, and it may take years to progress from normal to uncompensated hypothyroidism.

Adolescent↗
PubMed1993

Cause and course of psychopathology: some lessons from longitudinal data.

Case-control studies of clinic samples constitute the usual research method for the investigation of the causes and course of psychiatric disorder. However, they carry substantial disadvantages and if causal hypotheses are to be tested in rigorous fashion, it is necessary to use longitudinal research strategies applied to epidemiologically based samples. Their advantages are reviewed with respect to the use of 'experiments of nature' for testing causal mechanisms through the study of within-individual change over time in relation to some prospectively measured alteration in the risk variable. Attention is drawn to the value of longitudinal data in studying the processes involved in 'escape' from risk; in examining differential vulnerability to risk experiences; in validating diagnostic categories; in investigating the timing of disorders; and in evaluating the role of variables that cannot be recalled. The data from a range of longitudinal studies are used to note some of the key implications for developmental and psychopathological concepts.

Adolescent↗
PubMed1980

Lymphocyte transformation with mitogens and antigens during normal human pregnancy: a longitudinal study.

In a longitudinal analysis of immunological changes in normal human pregnancy, twenty-two pregnant women were studied, with blood samples taken before pregnancy, during its course, at delivery, and 3-5 months after delivery. The blood samples were frozen successively, using a cryobiological freezing system, and were stored until the whole longitudinal series was obtained. The collected material for a longitudinal series was then thawed and tested in one seance. Lymphocyte transformation tests were performed with stimulation with the mitogens phytohaemagglutinin (PHA), pokeweed mitogen (PWM), concanavalin A (Con A) and the specific antigens tuberculin purified protein derivative (PPD), Candida albicans (CA), Staphylococcus aureus (SA) and streptokinase/streptodornase (SK/SD). No changes were found in PHA or in PWM responses, whereas there were significant changes in the Con A response, with lowest values in the middle of pregnancy. PPD, CA, SA and SK/SD responses all reached lowest values towards the end of pregnancy, with increases subsequently, after delivery. These findings seem to show that T suppressor function is increased and B-lymphocyte function decreases during the course of pregnancy.

Candida albicans↗
PubMed2005

Effect of smoking on FEV decline in a cross-sectional and longitudinal study of a large cohort of Japanese males.

OBJECTIVE: The effects of cigarette smoking and smoking cessation on age-related pulmonary function decline was assessed in both cross-sectional and longitudinal studies. METHODOLOGY: In the cross-sectional study, pulmonary function data from 11,875 healthy asymptomatic males, aged between 35 and 74, were analysed and correlated with their smoking history and age. In the longitudinal study, changes in pulmonary function were monitored over a 5-year period in 1888 healthy males. RESULTS: The cross-sectional study showed that the difference in FEV(1) between male never smokers and current smokers was small at a younger age but increased with age. A beneficial effect on FEV(1) decline was observed in those who ceased smoking, even within the previous 12 months. Longitudinally, current smokers showed a more rapid decline in FEV(1) over the 5-year period than non-smokers. Those who ceased smoking had lower rates of decline in FEV(1) than those who continued to smoke. CONCLUSION: These results indicate that cigarette smoking is associated with a reduction in pulmonary function, and that smoking cessation has a beneficial effect on FEV(1) decline. Provision of a smoking cessation program for all smokers, especially those showing a rapid decline of FEV(1), should be considered as an important strategy to prevent progression of COPD.

Adult↗
PubMed2003

Aboriginal and Torres Strait Islander health research and the conduct of longitudinal studies: issues for debate.

The National Health and Medical Research Council, Research Agenda Working Group (RAWG), and the literature on Indigenous health have identified the need to fill gaps in descriptive data on Aboriginal and Torres Strait Islander health and noted both the lack of research with urban populations and the need for longitudinal studies. This paper presents some of the broad ethical and methodological challenges associated with longitudinal research in Indigenous health and focuses particularly on national studies and studies in urban areas. Our goal is to advance debate in the public health arena about the application of ethical guidelines and the conduct of longitudinal studies in Aboriginal and Torres Strait Islander communities. We encourage others to offer their experiences in this field.

Australia↗