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Results for “longitudinal data”

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PubMed2006

The factor structure and factorial invariance of the 12-item General Health Questionnaire (GHQ-12) across time: evidence from two community-based samples.

This study provides new knowledge about the factor structure of the 12-item General Health Questionnaire (GHQ-12; D. Goldberg, 1972) through the application of confirmatory factor analysis to longitudinal data, thereby enabling investigation of the factor structure, its invariance across time, and the rank-order stability of the factors. Two community-based longitudinal adult samples with 1-year (n = 640) and 6-year (n = 330) follow-up times were studied. As a result, the correlated 3-factor model (i.e., Anxiety/Depression, Social Dysfunction, and Loss of Confidence) showed a better fit with both samples than the alternative models. The correlated 3-factor structure was also relatively invariant across time in both samples, indicating that the scale has good construct validity. The rank-order stabilities of the factors were low across time, which suggests that the GHQ-12 measures temporal mental state.

Adult↗

PubMed2006

Use of inhaled corticosteroids and the risk of fracture.

BACKGROUND: Previous studies have found an association between the use of inhaled corticosteroids and fracture, but the extent to which this association is due to inhaled corticosteroids or to related factors, such as the severity of airflow obstruction, is disputed. We report a new approach in which we combine data on people with airflow obstruction from a large Medical Research Council study of the assessment and management of older people in the community with longitudinal data from their computerized general practice records. METHODS: Our cohort includes 1,671 study participants with a diagnosis of asthma or COPD (mean age, 80.6 years). We determined the dose-response relationship between inhaled corticosteroid exposure and time to first fracture using Cox regression, allowing for a wide range of potential confounding factors. RESULTS: During a mean follow-up period of 9.4 years, 982 patients (59%) received a prescription for an inhaled corticosteroid and 187 patients had a fracture. After adjusting for the effects of age and gender, we found a dose-related increase in fracture risk with exposure to inhaled corticosteroids (rate ratio for mean daily dose > 601 mug, 2.53; 95% confidence interval [CI], 1.65 to 3.89; overall trend p < 0.0001). The results were similar after adjusting for oral corticosteroid exposure, airflow obstruction diagnosis, historical fracture, and bronchodilator use (rate ratio, 4.21; 95% CI, 2.19 to 8.13), and also in the subset of people with no exposure to oral corticosteroids (rate ratio, 4.54; 95% CI, 1.23 to 16.74). CONCLUSIONS: Our findings provide further evidence that inhaled corticosteroid use is an independent risk factor for fracture.

Administration, Inhalation↗

PubMed1990

Analysis of craniofacial growth in Crouzon syndrome using landmark data.

Finite-element scaling analysis (FESA), generalized procrustes analysis (GPA), and Euclidean distance matrix analysis (EDMA) are applied in a two-dimensional study of craniofacial growth in normal children and those affected with Crouzon syndrome. Longitudinal data are used and growth is measured as change local to 10 craniofacial landmarks. Although details of the results vary among the methods, all 3 methods determine Crouzon growth to be different from normal. Nuances of the methods, especially the use of superimposition in GPA and lack of superimposition in 2 others are partly responsible for the varying results. Although Crouzon craniofacial morphology is often obvious at birth, this study demonstrates that there are general differences between normal postnatal growth patterns and those of the Crouzon individual. These patterns of malgrowth are in part responsible for the adult morphology of the Crouzon craniofacial complex.

Adolescent↗

PubMed2003

[Longitudinal study on osteoarthritis and bone metabolism].

OBJECTIVE: The relationship between Osteoarthritis (OA) and Osteoporosis (OP) is not well defined due to lacking in longitudinal data, mainly regarding correlations between biochemical factors and OA incidence. Aim of this paper was to investigate the predictive value for OA incidence of bone mass variations and of selected biochemical markers in healthy women participating in a population-based longitudinal study carried out in Naples (Italy). SUBJECTS AND METHODS: High completion rate (85.2%) and statistically adequate sample size were obtained: 139 women (45 to 79 years of age) were examined and follow up visit was performed after two years (24+/-2 months), following the same protocol. Patients underwent medical examination, questionnaire, anthropometric measurements, blood sampling and urine collection. Bone mineral density (BMD) measurement was performed by dual energy X-ray absorptiometry (DEXA) at the lumbar spine (L1-L4) and femoral neck. Radiographs of dorsal and lumbar spine in lateral view were performed at basal and at 24 months visits; a team of three experts scored radiographs using Kellgren and Lawrence grading. RESULTS: The score was calculated for two individual radiographic features (narrowing of the joint space, presence of osteophytes) and as a global score. Results show a relevant percentage, 23% up, of subjects presenting both OA and OP. In the cross-sectional study the presence of osteophytosis correlates with anthropometric variables and PTH levels. In the longitudinal study results show a correlation between serum vitamin D and delta score for osteophytosis (beta=0.02 p<0.05). CONCLUSIONS: Data obtained outline the importance of further studies on the pathogenetic link between OA and bone metabolism.

Absorptiometry, Photon↗

PubMed2004

Multivariate regression trees for analysis of abundance data.

Multivariate regression tree methodology is developed and illustrated in a study predicting the abundance of several cooccurring plant species in Missouri Ozark forests. The technique is a variation of the approach of Segal (1992) for longitudinal data. It has the potential to be applied to many different types of problems in which analysts want to predict the simultaneous cooccurrence of several dependent variables. Multivariate regression trees can also be used as an alternative to cluster analysis in situations where clusters are defined by a set of independent variables and the researcher wants clusters as homogeneous as possible with respect to a group of dependent variables.

Biometry↗

PubMed1999

Relating the classical covariance adjustment techniques of multivariate growth curve models to modern univariate mixed effects models.

The relationship between the modern univariate mixed model for analyzing longitudinal data, popularized by Laird and Ware (1982, Biometrics 38, 963-974), and its predecessor, the classical multivariate growth curve model, summarized by Grizzle and Allen (1969, Biometrics 25, 357-381), has never been clearly established. Here, the link between the two methodologies is derived, and balanced polynomial and cosinor examples cited in the literature are analyzed with both approaches. Relating the two models demonstrates that classical covariance adjustment for higher-order terms is analogous to including them as random effects in the mixed model. The polynomial example clearly illustrates the relationship between the methodologies and shows their equivalence when all matrices are properly defined. The cosinor example demonstrates how results from each method may differ when the total variance-covariance matrix is positive definite, but that the between-subjects component of that matrix is not so constrained by the growth curve approach. Additionally, advocates of each approach tend to consider different covariance structures. Modern mixed model analysts consider only those terms in a model's expectation (or linear combinations), and preferably the most parsimonious subset, as candidates for random effects. Classical growth curve analysts automatically consider all terms in a model's expectation as random effects and then investigate whether "covariance adjusting" for higher-order terms improves the model. We apply mixed model techniques to cosinor analyses of a large, unbalanced data set to demonstrate the relevance of classical covariance structures that were previously conceived for use only with completely balanced data.

Biometry↗

PubMed1995

Information on drug use in the elderly: a comparison of pharmacy, general-practitioner and patient data.

Management of pharmacotherapy by the pharmacist and the general practitioner can be a difficult task in elderly patients in whom there is a high concomitant, long-term drug use. Adequate information on drug use is essential in managing pharmacotherapy as well as in an accurate assessment of drug exposure in pharmacoepidemiologic studies. In this study data from computerized pharmacy records, general-practitioner registries and home interviews with 100 elderly patients were compared. Pharmacy records contained 80% of all the prescriptions found at the home interviews, while in general-practitioner data 40% could be traced. Use of drugs dispensed long ago reduced the validity of pharmacy and general-practitioner data. Data on analgesics (70% was found) and respiratory drugs (68%) were less traceable compared to cardiovascular (83%) and psychotropic drugs (81%). Automated pharmacy records are an important source of longitudinal data on drug use and will improve the assessment of drug exposure in pharmacoepidemiologic studies and optimize pharmaceutical care.

Aged↗

PubMed2000

Longitudinal changes in the contribution of genetic and environmental influences to symptoms of depression in older male twins.

Genetically informative longitudinal data on self-reported symptoms of depression allow for an investigation of the causes of stability and change in depression symptoms throughout adult life. In this report, the authors investigated the relative contribution of genetic and environmental influences to symptoms of depression in 83 monozygotic and 84 dizygotic male twin pairs from the National Heart, Lung, and Blood Institute (NHLBI) Twin Study. Participants first completed the Center for Epidemiologic Studies-Depression (CES-D) scale in 1985-1986 and again during 1995-1997. Mean age of twins at baseline was 63 years, range 59 to 70. From cross-sectional genetic analyses we estimated the heritability of CES-D to be 25% (95% confidence interval [CI], 11%-39%) at baseline and 55% (95% CI, 40%-71%) at follow-up. Fitting longitudinal genetic models to the two-wave data, we found that stability of symptoms over the 10-year follow-up was due primarily to continuity of genetic influences.

Adult↗

PubMed2002

Theory and methods in the study of the development of case and agreement: a response to Schütze.

Two recent papers Wexler, Schütze & Rice (1998) and Rispoli (1999a) reach different conclusions concerning the relationship between finiteness marking and pronoun case errors. Wexler et al. claim they are linked, whereas Rispoli finds little evidence for such a linkage. Wexler et al. discounted data from children who made pronoun case errors in 100% of their attempts at a subject pronoun, whereas Rispoli (1999a) included data from such children. This methodological difference may account for our differing conclusions. Schütze (2001) defends the omission of these data, claiming that children who make a pronoun case error 100% of the time do so because the correct pronoun case form is not in the child's productive inventory. Longitudinal data is presented showing the inadequacy of this assumption. Children may err without variation after a period of variation, indicating that these children have knowledge of the correct form. Apparent methodological differences between the two papers reveal deeper theoretical biases. The paradigm building approach taken by Rispoli views longitudinal variation of this sort as a reflection of lexical retrieval principles at work in a developing paradigm. In contrast, the Agr/Tns Omission Model of Wexler et al. finds such variation an uncomfortable inconvenience.

Child Language↗

PubMed1997

Benefits and disadvantages of tooth-coloured alternatives to amalgam.

OBJECTIVES: To give the practising dentist scientifically based data to assist him/her in the responsible decision-making process necessary to weigh the options available to the patient if she/he prefers not to have an amalgam placed. DATA SOURCES: Based on the literature and on the research work, which was done in the author's department, the indications and limitations of the known alternatives of amalgam were formulated. DESCRIPTION OF ALTERNATIVES TO AMALGAM: With the exception of cast gold restorations, all alternatives require the strict use of adhesive techniques. When compared with similar amalgam restorations, placing composite restorations (if they are indicated) takes approximately 2.5 times longer because complex incremental techniques are needed. Despite all the efforts, direct composite restorations placed in large cavities still show unacceptable amounts of marginal openings. Tooth-coloured inlays are a better alternative for large restorations. These restorations must be inserted with adhesive techniques. With composite inlays it is difficult to achieve a composite-composite bond. Ceramic inlays may be micromechanically bonded to the luting composite. They all show clinically a good marginal behaviour and the use of ultrasonic energy may further simplify the application technique of aesthetic inlays. STUDY SELECTION: Papers describing the different techniques were used as a base for the corresponding chapter. To assess and compare the longevity of the different restoration types, literature data were used. We limited ourselves to papers reporting at least 5-year clinical data. Longitudinal, clinically controlled studies were preferred. However, to be more complete, retrospective, cross sectional studies were also included. LONGEVITY OF POSTERIOR RESTORATIONS: Amalgam shows excellent longevity data with studies up to 20 years. The average annual failure rate is 0.3-6.9%. Posterior composites are in the same range (0.5-6.6%), however, the study times are much shorter (max. 10 years). For tooth-coloured inlays much less data are available. Longevity is reported up to 6 years with annual failure rates of 0.6-5%. CONCLUSIONS: All aesthetic alternatives to amalgam require more complex procedures and more time. If cost benefit considerations are a concern, amalgam is still the most convenient restorative material for posterior teeth.

Bicuspid↗

PubMed1999

The influence of hypothyroidism and thyroid replacement therapy on stimulated parotid flow rates.

OBJECTIVE: The purpose of this study was to determine, through use of cross-sectional and longitudinal data, whether hypothyroidism and its treatment with thyroid hormones have a significant effect on the production of stimulated parotid flow rates. STUDY DESIGN: From the Baltimore Longitudinal Study of Aging (NIA, NIH), subjects with hypothyroidism taking and not taking thyroid replacement therapy were evaluated for the production of 2% citrate-stimulated parotid saliva in a cross-sectional and longitudinal investigation. Comparisons were made with nonmedicated healthy control subjects. RESULTS: Cross-sectional analyses revealed that stimulated parotid flow rates were not significantly different between healthy controls, subjects with hypothyroidism on thyroid replacement therapy, and subjects with hypothyroidism not on thyroid replacement therapy. In general, longitudinal analyses revealed no significant differences over time in stimulated parotid flow rates between healthy controls and subjects with hypothyroidism. CONCLUSIONS: Hypothyroidism and the concomitant use of thyroid replacement therapy do not cause significant changes in the production of stimulated parotid saliva.

Adult↗

PubMed2006

Cost-effectiveness analysis for health communication programs.

This article describes methods for analyzing the cost-effectiveness of health communication programs, focusing in particular on estimating program effectiveness with econometric methods that address experimental and quasi-experimental designs (and their absence), national or subnational program coverage, and endogenously targeting of programs. Experimental designs provide a gold standard for assessing effectiveness but are seldom feasible for large-scale health communication programs. Even in the absence of such designs, however, fairly simple methods can be used to examine intermediate objectives, such as program reach, which in turn can be linked to program costs to estimate cost effectiveness. When moving beyond program reach to behavioral or other outcome measures, such as contraceptive use or fertility, or when faced with full-coverage national programs, more elaborate data and methods are required. We discuss data requirements and assumptions necessary in each case, focusing on single-equation multiple regression models, structural equations models, and fixed effects estimators for use with longitudinal data, and then describing how cost information can be incorporated into econometric models so as to get measures of the cost-effectiveness of communication interventions.

Cost-Benefit Analysis↗

PubMed1999

A hierarchical Bayesian model to predict the duration of immunity to Haemophilus influenzae type b.

A hierarchical Bayesian regression model is fitted to longitudinal data on Haemophilus influenzae type b (Hib) serum antibodies. To estimate the decline rate of the antibody concentration, the model accommodates the possibility of unobserved subclinical infections with Hib bacteria that cause increasing concentrations during the study period. The computations rely on Markov chain Monte Carlo simulation of the joint posterior distribution of the model parameters. The model is used to predict the duration of immunity to subclinical Hib infection and to a serious invasive Hib disease.

Antibodies, Bacterial↗

PubMed2004

Longitudinal changes in aerobic power in older men and women.

The purpose of this study was to describe the longitudinal (10 yr) decline in aerobic power [maximal O(2) uptake (Vo(2 max))] and anaerobic threshold [ventilatory threshold (T(Ve))] of older adults living independently in the community. Ten years after initial testing, 62 subjects (34 men, mean age 73.5 +/- 6.4 yr; 28 women, 72.1 +/- 5.3 yr) achieved Vo(2 max) criteria during treadmill walking tests to the limit of tolerance, with T(Ve) determined in a subset of 45. Vo(2 max) in men showed a rate of decline of -0.43 ml.kg(-1).min(-1).yr(-1), and the decline in Vo(2 max) was consequent to a lowered maximal heart rate with no change in the maximum O(2) pulse. The women showed a slower rate of decline of Vo(2 max) of -0.19.ml.kg(-1).min(-1).yr(-1) (P < 0.05), again with a lowered HR(max) and unchanged O(2) pulse. In this sample, lean body mass was not changed over the 10-yr period. Changes in Vo(2 max) were not significantly related to physical activity scores. T(Ve) showed a nonsignificant decline in both men and women. Groupings of young-old (65-72 yr at follow-up) vs. old-old (73-90 yr at follow-up) were examined. In men, there were no differences in the rate of Vo(2 max) decline. The young-old women showed a significant decline in Vo(2 max), whereas old-old women, initially at a Vo(2 max) of 19.4 +/- 3.1 ml.kg(-1).min(-1), showed no loss in Vo(2 max). The longitudinal data, vs. cross-sectional analysis, showed a greater decline for men but similar estimates of the rates of change in women. Thus the 10-yr longitudinal study of the cohort of community-dwelling older adults who remained healthy, ambulatory, and independent showed a 14% decline in Vo(2 max) in men, and a smaller decline of 7% in women, with the oldest women showing little change over the 10-yr period.

Aged↗

PubMed2005

Different mechanisms to explain the reversed effects of mental health on work characteristics.

OBJECTIVES: The number of longitudinal studies reporting evidence for reversed effects of strain on work is growing, but evidence regarding the mechanisms underlying such effects is scarce. In this study, earlier longitudinal findings were reviewed, and the following four mechanisms for reversed effects were proposed that reflect within-person or environmental changes: (i) the rosy perception mechanism, (ii) the gloomy perception mechanism, (iii) the upward selection mechanism, and (iv) the drift mechanism. METHODS: These mechanisms were tested using structural equation modeling and longitudinal data from a Dutch four-phase study (N=1588 participants). RESULTS: The results revealed that work characteristics and mental health influenced each other reciprocally and longitudinally. The reversed effects were examined in more detail, and it was found that these could be accounted for by both within-person and environmental change mechanisms. The rosy perception mechanism was found to explain the positive effects from health on job demands; the upward selection mechanism explained the positive (environmental) effects from health on job control; the gloomy perception mechanism explained the reversed (evaluation) effects from health on supervisory social support. No support was found for the drift mechanism. CONCLUSIONS: Mechanisms that may explain reversed causation are yet poorly understood. The main contribution of the present study lies in the fact that it proposes (i) a conceptual framework with which to analyze the effects of health on work characteristics and (ii) methods for testing these mechanisms. The study revealed that there is good reason to pursue research on reversed causality.

Adult↗

PubMed1994

Longitudinal changes in time domain spirogram indices and their variability.

The purpose of this study was to describe longitudinal changes in time domain spirogram indices and their variability. We therefore measured forced expiratory spirograms of 326 middle-aged male employees in two asbestos-using factories four times over 5 yrs. From the original sample of 326, 225 healthy subjects, who provided reliable results for three or more surveys, were selected for analysis. The mean and standard deviation of transit time and their log-transformed values (MTT, STT, ln(MTT), and ln(STT), respectively), as well as two indices of the estimated time constant distribution (Mu and Sigma, respectively) were analysed using a longitudinal model. The longitudinally estimated annual increase of MTT, STT, ln(MTT), and ln(STT) was about three times larger than the cross-sectional estimate, whilst they were comparable in Mu and Sigma. A highly significant contribution of between-subject variability was found in all indices. This was particularly remarkable in the mean components. The between-subject variability was about eight times larger than the error variance in Mu, and three times in MTT and ln(MTT). We conclude that the longitudinal data of transit time indices should not be compared with cross-sectional reference values, and that the magnitude of error variance of these indices in longitudinal repeated measurements will be rather less than the cross-sectional counterpart reported previously.

Adult↗

PubMed1994

Understanding the dynamics of the HIV epidemic among Italian intravenous drug users: a cross-sectional versus a longitudinal approach.

We studied annual human immunodeficiency virus (HIV) seroprevalence and incidence in a large number of intravenous drug users attending drug treatment centers in three Italian urban areas. We also evaluated risk factors for HIV seropositivity and for HIV seroconversion. The results showed that HIV prevalence and incidence are declining. HIV prevalence declined dramatically in study participants that were < 25 years old. Prevalent HIV cases were associated with older age and longer duration of intravenous drug use; however, short duration of drug use increased the risk of seroconversion. The findings of our study suggest that comparing cross-sectional and longitudinal data contributes to a better understanding of the dynamics of the HIV epidemic among intravenous drug users.

Adult↗

PubMed1995

Maturation of electroretinograms and visual evoked potentials in preterm infants.

Electroretinograms (ERGs) and visual evoked potentials (VEPs) to flash stimulation were recorded from 51 infants (gestational age 26 to 42 weeks; post-conceptional age (PCA) 31 to 47 weeks) to give cross-sectional data on the maturation of these responses. Sequential recordings were taken from a separate group of 24 preterm infants (gestational age 28 to 33 weeks) to give longitudinal data. There was a significant decrease in ERG a-wave latency and increase in a-b amplitude with increasing PCA in both groups. For the VEPs there was a significant decrease in latency of the early negative component (N1) and the major positive component (P2). Comparison between recordings made on preterm infants with those from term infants at an equivalent PCA suggested faster maturation of VEPs in the extra-uterine environment, but no difference in maturation of the ERG.

Brain↗