Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “longitudinal”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed1992

The uremic dyslipidemia: a cross-sectional and longitudinal study.

Patients on maintenance hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) exhibit numerous disturbances of serum lipids and apoproteins that may contribute to their high cardiovascular mortality. Cross-sectional studies have found that lipid levels are inversely related to time on dialysis. However, it is not known whether this association is the result of the attrition of hyperlipidemic patients or a decrease in lipid levels over time in all patients. Additionally, few studies have investigated the effect of dialysis modality on the lipoprotein disturbances of uremia adjusting for the confounding influences of demographics, or nutritional and endocrine status. To address these issues, we undertook a cross-sectional and longitudinal study of lipids, apoproteins, and atherogenic risk ratios in patients maintained on HD and CAPD. Patients were enrolled in annual cohorts from 1987 to 1990 and monitored until 1991. A total of 196 HD and 77 CAPD patients were studied. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), apoprotein (apo) A-I, and apo B were measured on enrollment and remeasured annually in survivors through 1990. Using multivariate methods, we examined the relationship of the lipids, apoproteins, their respective ratios, and their changes over time, to a broad range of clinical factors and to mortality. Compared with HD patients, CAPD patients had significantly higher TC, apo A-I, and apo B, and a significantly lower apo A-I/apo B ratio. Serum albumin correlated directly with TC and apo B and inversely with apo A-I/apo B. For patients with normal serum albumin (> or = 3.5 g/dL [35 g/L]), CAPD patients had a significantly higher TC/HDL-C than HD patients; otherwise the ratios were similar for CAPD and HD. Independent influences on lipoprotein levels in HD and CAPD patients were also demonstrated for race, gender, and diabetes, but not for parathyroid hormone (PTH) levels. For both dialysis modalities, patients who died had significantly lower TC and apo B, and significantly higher apo A-I/apo B throughout their entire courses compared with survivors. In the subset of patients followed longitudinally for 2 or more years, apo B tended to decrease with time, but TC, HDL-C, and apo A-I were stable. The longitudinal changes in lipoproteins did not correlate with outcome or other factors. In conclusion, CAPD patients have more atherogenic lipoprotein profiles than HD patients. Improved visceral protein nutritional status, as defined by serum albumin level, is associated with hyperlipidemia and, especially vor CAPD, worsened atherogenic risk ratios.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMedDate not supplied

Behavioral traits and marijuana use and abuse: a meta-analysis of longitudinal studies.

The present study uses data from a meta-analytic archive of prospective longitudinal studies (N= 3206) to examine the association between negative affect, emotionality, and unconventionality on the use, misuse, and abuse of marijuana. For each of the three constructs, variables were divided into two categories--a "trait," which refers to a personality characteristic or attitudes and beliefs, and a "behavior," which refers to something that a subject does. A total of 63 reports from 40 studies provided effect sizes on the bivariate relationship of one or more of these six categories with current or later marijuana use, misuse, or abuse. Pooling partially redundant estimates for independence reduced the dataset from 358 estimates to 93 aggregated effect sizes for the cross-sectional data included in the archive, and from 478 estimates to 73 aggregated effect sizes for the longitudinal data. The effect sizes obtained from the longitudinal data were modest, none above 0.20. Indeed, only those for unconventionality-trait and emotionality-trait and marijuana use were of sufficient magnitude and reliably to warrant attention. Of the behavioral constructs assessed using the cross-sectional data, only unconventionality was associated with marijuana use and misuse. The emotionality-behavior construct and both unconventionality constructs were most strongly associated with marijuana abuse. The conceptual and methodological limitations of the study along with the implications of its findings for prevention are briefly discussed.

Behavior, Addictive↗
PubMed2002

Longitudinal motor development of "apparently normal" high-risk infants at 18 months, 3 and 5 years.

BACKGROUND: Motor development appears to be more affected by premature birth than other developmental domains, however few studies have specifically investigated the development of gross and fine motor skills in this population. AIM: To examine longitudinal motor development in a group of "apparently normal" high-risk infants. SETTING: Developmental follow-up clinic in a perinatal centre. STUDY DESIGN: Longitudinal observational cohort study. SUBJECTS: Fifty-eight infants born less than 29 weeks gestation and/or 1000 g and without disabilities detected at 12 months. OUTCOME MEASURES: Longitudinal gross and fine motor skills at 18 months, 3 and 5 years using the Peabody Developmental Motor Scales. The HOME scale provided information of the home environment as a stimulus for development. RESULTS: A large proportion (54% at 18 months, 47% at 3 years and 64% at 5 years) of children continued to have fine motor deficits from 18 months to 5 years. The proportion of infants with gross motor deficits significantly increased over this period (14%, 33% and 81%, p<0.001), particularly for the 'micropreemies' (born <750 g). In multivariate analyses, gross motor development was positively influenced by the quality of the home environment. CONCLUSIONS: A large proportion of high-risk infants continued to have fine motor deficits, reflecting an underlying problem with fine motor skills. The proportion of infants with gross motor deficits significantly increased, as test demands became more challenging. In addition, the development of gross and fine motor skills appears to be influenced differently by the home environment.

Child Development↗
PubMed2003

Genomic studies in AIDS: problems and answers. Development of a statistical model integrating both longitudinal cohort studies and transversal observations of extreme cases.

Genomic studies developed to understand HIV-1 infection and pathogenesis have often lead to conflicting results. This is linked to various factors, including differences in cohort design and selection, the numbers of patients involved, the influence of population substructure, the ethnic origins of the participants, and phenotypic definition. These difficulties in the interpretation of results are examined through published studies on the role of polymorphisms in HLA and the chemokine receptors genes in AIDS. Our analysis suggests that the use of haplotypes will strengthen the results obtained in a given cohort, and meta-analysis including multiple cohorts to gather large-enough numbers of patients should also allow clarification of the genetic associations observed. A P-value of 0.001 appears to be a good compromise for significance on candidate genes in a genetic study. Due to the generally limited size of available cohorts, results will have to be validated in other cohorts. We developed a model to fit transversal case studies (extreme case-control studies) with longitudinal cohorts (all-stages patients) for observations on two gene polymorphisms of CCR5 and NQO1. Interestingly, we observe a protective effect for the CCR5-Delta32 mutant allele in 95% of the simulations based on that model when using a population of 600 subjects; however, when using populations of 250 subjects we find a significant protection in only 59% of the simulations. Our model gives thus an explanation for the discrepancies observed in the various genomic studies published in AIDS on CCR5-Delta32 and other gene polymorphisms: they result from statistical fluctuations due to a lack of power. The sizes of most seroconverter cohorts presently available seem thus insufficient since they include less than a few hundred subjects. This result underlines the power and usefulness of the transversal studies involving extreme patients and their complementarity to longitudinal studies involving seroconverter cohorts. The transposition approach of extreme case-control data into longitudinal analysis should prove useful not only in AIDS but also in other diseases induced by chronic exposure to a foreign agent or with chronic clinical manifestations.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Longitudinal ventricular function: normal values of atrioventricular annular and myocardial velocities measured with quantitative two-dimensional color Doppler tissue imaging.

OBJECTIVE: Quantitative 2-dimensional color Doppler tissue imaging is a new method to reveal impairment of left ventricular (LV) and right ventricular (RV) longitudinal function, which is a potential marker of early myocardial disease. The aim of this study was to obtain normal values for atrioventricular annular and regional myocardial velocities using this method. METHODS: A total of 123 healthy patients (age range: 22 to 89 years) underwent echocardiography including color Doppler tissue imaging using a scanner (Vivid 5, GE Vingmed, Horten, Norway) with postprocessing analysis (Echopac 6.3, GE Vingmed). Regional myocardial velocities were measured at 12 LV segments in 3 apical views and 2 segments of the free RV wall. Mitral annular velocities from 6 sites, and tricuspid annular velocities at its lateral site, were also assessed. At each site, systolic (S(m)), early diastolic (E(m)), and late diastolic (A(m)) velocities were measured, and the E(m)/A(m) ratio was calculated. RESULTS: Patients were classified into 4 groups aged 20 to 39, 40 to 59, 60 to 79, and >/=80 years. Mitral annular velocity and regional LV myocardial S(m) and E(m) progressively decreased with age. A(m), whereas low in the youngest age group, increased significantly in patients more than 40 years of age. The E(m)/A(m) ratio gradually declined with aging. There were no differences between age groups in S(m) measured at the tricuspid annulus and free RV wall, but the pattern of age-related changes of diastolic velocities and E(m)/A(m) ratio was the same as in the LV. Slight but significant sex-related differences were observed in middle-aged groups. The intraobserver and interobserver reproducibility was highest for atrioventricular annular velocities. CONCLUSIONS: A progressive decrease in S(m) reveals a decline in longitudinal systolic LV function with age, whereas systolic RV function remains unaffected. Atrioventricular annular velocity and regional E(m) decrease with aging in both ventricles, suggesting a deterioration in the diastolic properties of the myocardium, whereas A(m) increases from middle age implying a compensatory augmentation of atrial function. The study results can be used as reference data for the quantitative assessment of longitudinal LV and RV function in patients with cardiac disease.

Adult↗
PubMed2000

Evolution of self-rated health status in the elderly: cross-sectional vs. longitudinal estimates.

We assessed the perceived health status evolution among elderly subjects and examined the age-related differences in perceived health when comparing estimates obtained from cross-sectional and longitudinal approaches. Data come from a cohort of non-institutionalized individuals aged 65 years or older, living in Barcelona, Spain. One thousand three hundred fifteen (1315) elderly were successfully interviewed at baseline in 1986 and 754 (84.6% of the eligible) at the re-assessment (1993-1994). Estimates of change in perceived health status were calculated based on cross-sectional and longitudinal approaches. Cross-sectionally, no significant differences in the proportion of individuals with poor self-rated health were found (40.5 vs. 42.5%, P = 0.90). Among survivors, the proportion of individuals with poor health increased from 37.8% to 55.1% (P < 0.01), an 8.7-fold decline of perceived health when compared with the cross-sectional estimates. Comorbidity (aOR 2.1; 95%CI: 1.4-3.3) and no education (aOR 1.9; 95%CI: 1.1-3.2) were associated with a decline in health status after adjusting by baseline health status. We recommend the use of longitudinal studies to understand the evolution of perceived health in the elderly.

Aged↗
PubMed2003

A longitudinal study of brain morphometrics using quantitative magnetic resonance imaging and difference image analysis.

Serial quantitative magnetic resonance imaging (MRI) allows the detection of subtle volumetric changes in brain volume. We used serial volumetry and voxel-based difference image analysis to quantify and characterize longitudinal changes in the hippocampus, cerebellum, and neocortex in younger and middle-age individuals. Paired volumetric MRI brain scans 3.5 years apart were performed on 90 healthy subjects 14 to 77 years old. Quantitative assessment of registered images included hippocampal volumetry, cerebellar volumetry, and automatically determined regional brain volumes. Longitudinal volume changes in three age epochs (<35, 35-54, >54 years) were compared and neocortical changes beyond regions of interest were visualized using filtered difference images. Cross-sectional analysis revealed a significant association between age and reduction in all brain volumes except hippocampal volume. Changes in normalized hippocampal and white matter volume were significantly different among the three groups. Individual analysis revealed 5 subjects with significant longitudinal volume changes lying outside the normative range. Difference image analysis showed global involutional changes in the >54 age group. Our findings suggest that cross-sectional observations in intracranial volume, cerebellar volume, and gray matter volume are likely to reflect uniform rates of volume loss or secular changes. Accelerated brain atrophy was seen from the age of 35-54 and increased rates of hippocampal atrophy from the age of 54. Our findings emphasize the importance of controlling for age effects when studying pathological brain changes over a wide age range.

Adolescent↗
PubMed2000

Longitudinal nutrient intake patterns of US adolescent women: the Penn State Young Women's Health Study.

PURPOSE: To use longitudinal nutrient intake data to determine whether dietary patterns remain consistent (or "track") as U.S. females progress from age 12 to 18 years. METHODS: Three-day diet records were collected at regular intervals over 6 years from participants in the Penn State Young Women's Health Study. Eighty-one subjects remained in the cohort during the study period. Tracking in body weight, in dietary intake of fat, sugar, iron, vitamin C, and in a total dietary score (TDS) was assessed using quartile-ranking analysis, year-to-year Pearson correlation analysis, and longitudinal linear analysis. RESULTS: Rank analysis revealed that subjects maintained their relative quartile positions for body weight throughout the study period, and year-to-year correlation coefficients for this variable were .93-.94. In contrast, rank and correlation analyses showed that the subjects did not track strongly with respect to any nutrient variable. Age 12 to 18 years correlation coefficients ranged from r = .04 for fat intake to r = .15 for the TDS. In longitudinal linear models, slopes differed in direction and significance across the original quartiles for nutrient intake, indicating varying dietary trends over time within the study population. CONCLUSIONS: Nutrient intake patterns do not track strongly throughout adolescence among U.S. females.

Adolescent↗
PubMed2005

A longitudinal study of growth patterns in schoolchildren in one Taipei District. II: Sitting height, arm span, body mass index and skinfold thickness.

BACKGROUND: It has been suggested that longitudinal rather than cross-sectional growth standards be used to assess individual growth patterns. Thus, the aim of this study was to follow boys and girls throughout their pubertal years, so that a mixed longitudinal growth curve of height, weight, sitting height, arm span, skinfold thickness, body mass index (BMI), and the ratio of sitting height or arm span to stature, could be obtained. METHODS: A defined group of 1,139 healthy schoolchildren (570 boys and 569 girls) from the Shih-Pai district of Taipei were followed longitudinally for 4 years. Anthropometric measurements of height, weight, sitting height, arm span, skinfold thickness, and BMI, were obtained for each child. RESULTS: Peak sitting-height velocities of 6.1 cm/year (boys) and 6.3 cm/year (girls) were seen at 8.5 years. The second peak of sitting-height velocity occurred at a mean age of 12.5 years for boys and 11.5 years for girls. Sitting-height velocity for the whole year covering the second peak was 4.6 cm in boys and 3.2 cm in girls. Peak arm-span velocity was seen at 13.5 years for boys and 8.5 years for girls, and arm-span velocity for the whole year covering this peak was 8.4 cm/year for boys and 8.1 cm/year for girls. CONCLUSION: These data provide growth patterns for Chinese children aged 8-18 years living in a Taipei district, with percentile charts for sitting height, arm span, BMI, and skinfold thickness.

Adolescent↗
PubMed2001

Circadian and longitudinal variation of serum C-telopeptide, osteocalcin, and skeletal alkaline phosphatase in C3H/HeJ mice.

Inbred strains of mice are increasingly being used as an animal model to investigate skeletal disorders relevant to humans. In the bone field, one of the most convenient endpoints for evaluating genetic, physiological, or pharmaceutical perturbations is the use of biochemical markers. To apply biochemical markers in an effective manner, it is of key importance to establish the biological variation and appropriate sampling time. In this study, we evaluate two components: (i) circadian changes, and (ii) longitudinal variation for three serum markers, osteocalcin, C-telopeptide, and skeletal alkaline phosphatase (sALP), using 6-week-old C3H/HeJ (C3H) mice. To study circadian rhythms, the mice were randomly divided into eight groups of 15 mice each. Blood was collected at 3 h intervals, starting at 9:00 A.M. and continuing until 6:00 A.M. the next day. To determine whether circadian rhythm is intrinsically regulated or influenced by restricted food intake, it was also studied after a 12 h fasting period. Serum osteocalcin and C-telopeptide levels were measured by enzyme-linked immunoassay (ELISA) and skeletal alkaline phosphatase by a kinetic assay. The results demonstrated significant circadian variations in osteocalcin and C-telopeptide levels with a peak value between 0900 and 1200 h during daytime and a nadir between 15:00 and 18:00 h. The peak levels of C-telopeptide and osteocalcin were 26%-66% higher as compared with 24 h mean values. The pattern of the circadian variation of C-telopeptide and osteocalcin was similar in female and male animals and was not significantly affected by restricted food intake. The sALP levels were only marginally affected by the circadian rhythm. Longitudinal variations, expressed as coefficient of variation (CV), for osteocalcin, C-telopeptide, and sALP concentrations were 17%, 14%, and 16%, respectively. In addition, the longitudinal variations were not significantly influenced by the time of blood collection in sALP and osteocalcin levels, whereas C-telopeptide levels showed significantly higher within-subject day-to-day variation in morning samples, as compared with blood samples collected in the afternoon. The results highlight the importance of: (i) the timing of sample collection for appropriate interpretation of the bone marker data; and (ii) using the appropriate number of samples based on the variance obtained herein.

Alkaline Phosphatase↗
PubMed1994

Neurasthenia in a longitudinal cohort study of young adults.

This study examines the concept of neurasthenia in a longitudinal cohort of young adults selected from a community sample of the canton of Zurich, Switzerland. The major focus is on the validity of the case definition of neurasthenia. Close approximations of the proposed descriptive and research definitions of the ICD-10 are employed as well as the concept of 'irritable weakness' as described in 1831 by Kraus (1926-1932). The prevalence of neurasthenia defined according to the ICD-10 criteria was: 1% across 10 years and 0.9% in 1988 for a duration criterion of > or = 3 months; and 8.1% across 10 years and 12% in 1988 for a duration criterion of > or = 1 month. The duration criterion of > or = 3 months appeared to be excessively restrictive to represent individuals with neurasthenia in the community. Subjects with 1 month episodes of neurasthenia exhibited sufficient differences from controls and similarities to subjects with anxiety or depressive disorders to justify a 1 month duration criterion for neurasthenia in community samples. The clinical significance of neurasthenia was indicated by the magnitude of subjective distress, and occupational and social impairment reported by the majority of the cases. Prospective assessment of the longitudinal course of neurasthenia revealed that approximately 50% of the cases continued to exhibit this disorder at follow-up. Our findings suggest that neurasthenia is equally likely to represent an early manifestation of affective illness as it is a consequence in those neurasthenic subjects who exhibited comorbid affective disorders. The magnitude, chronicity, impairment, longitudinal stability and distinction from anxiety and depression associated with this condition in the general population, suggest that neurasthenia is an important diagnostic entity for which additional validation studies should be undertaken.

Adult↗
PubMed2004

How accurate is recall of key symptoms of depression? A comparison of recall and longitudinal reports.

BACKGROUND: Assessment of lifetime major depression is usually made from a single interview. Most previous studies have investigated reliability. Comparison of recall of key symptoms and longitudinal reports shows the accuracy of recall, not just reliability. METHOD: At age 25, 1003 members of the Christchurch Health and Development Study cohort were asked to recall key symptoms of depression (sadness, loss of interest) up to age 21. This recall was compared with longitudinal reports at ages 15, 16, 18 and 21 years. Diagnosis was by DSM-III-R and DSM-IV criteria. RESULTS: Only 4% of those without previous reports recalled key symptoms. Of those with a diagnosis of depression up to age 21, 44% recalled a key symptom. Measures of severity of an episode (number of symptoms, impairment, duration, suicidally) and chronicity (years with a diagnosis, years with suicidal ideation) all strongly predicted recall. Current key symptoms increased recall, even after taking account of severity and chronicity. Being female and receiving treatment also predicted recall, although odds ratios were reduced to 1.6-1.7 when all other predictors were included. Comparison of risk factors for key symptoms showed similar results from longitudinal reports and recall. Sexual abuse, neuroticism, lack of parental attachment, gender, physical abuse and maternal depression were major risk factors in both sets of analyses. CONCLUSIONS: Forgetting of prior episodes of depression was common. Severity, chronicity, current depression, gender and treatment predicted recall. Lifetime prevalence based on recall will be markedly underestimated but the identification of major risk factors may be relatively little impaired.

Adolescent↗
PubMed2006

Longitudinal studies of PTSD: overview of findings and methods.

Posttraumatic stress disorder (PTSD) has a discernible starting point and typical course, hence the particular appropriateness of longitudinal research in this disorder. This review outlines the salient findings of longitudinal studies published between 1988 and 2004. Studies have evaluated risk factors and risk indicators of PTSD, the disorder's trajectory, comorbid disorders and the predictive role of acute stress disorder. More recent studies used advanced data analytic methods to explore the sequence of causation that leads to chronic PTSD. Advantages and limitations of longitudinal methods are discussed.

Cognition Disorders↗
PubMed2002

The Hospital for Sick Children, Toronto, Longitudinal ERG study of children on vigabatrin.

The purpose of this longitudinal study was to identify changes in ERG responses associated with vigabatrin treatment. We accomplished this by recording longitudinally ERGs in children before and during vigabatrin treatment and comparing results between children on vigabatrin monotherapy and those taking additional anticonvulsive medications. Thirty-three children on vigabatrin therapy were tested; the duration between visits was approximately 6 months. Thirteen children were assessed initially before starting vigabatrin therapy and seven were assessed soon after (age range 1.5-126 months, median 6 months). The remaining 13 patients were already on vigabatrin at the time of initial visit (age range 6.5-180 months, median 16 months). ERGs were tested using the standard protocol established by the International Society for Clinical Electrophysiology of Vision, with Burian-Allen bipolar contact-lens electrodes. In addition to standard responses we recorded photopic oscillatory potentials (OPs). All 33 patients were tested longitudinally on at least two occasions and 11 were tested on three occasions. For children whose only anticonvulsive drug was vigabatrin there was a significant curvature (quadratic function, p < 0.05) of the predicted cone b-wave amplitude with time; exhibited as increase in b-wave amplitude followed by subsequent decrease. Descriptive data demonstrated the same pattern in the group taking anticonvulsive medications in addition to vigabatrin. In most children the flicker amplitude declined between 6 months and 1 year of vigabatrin treatment. Our data demonstrated that rod responses, which may be abnormal before initiation of vigabatrin, did not change substantially with vigabatrin treatment.

Adolescent↗
PubMed2002

Joint modeling of event time and nonignorable missing longitudinal data.

Survival studies usually collect on each participant, both duration until some terminal event and repeated measures of a time-dependent covariate. Such a covariate is referred to as an internal time-dependent covariate. Usually, some subjects drop out of the study before occurrence of the terminal event of interest. One may then wish to evaluate the relationship between time to dropout and the internal covariate. The Cox model is a standard framework for that purpose. Here, we address this problem in situations where the value of the covariate at dropout is unobserved. We suggest a joint model which combines a first-order Markov model for the longitudinally measured covariate with a time-dependent Cox model for the dropout process. We consider maximum likelihood estimation in this model and show how estimation can be carried out via the EM-algorithm. We state that the suggested joint model may have applications in the context of longitudinal data with nonignorable dropout. Indeed, it can be viewed as generalizing Diggle and Kenward's model (1994) to situations where dropout may occur at any point in time and may be censored. Hence we apply both models and compare their results on a data set concerning longitudinal measurements among patients in a cancer clinical trial.

Algorithms↗
PubMed2003

Interpretation of change and longitudinal validity of the quality of life for respiratory illness questionnaire (QoLRIQ) in inpatient pulmonary rehabilitation.

The quality of life for respiratory illness questionnaire (QoLRIQ) is an outcome measure for patients with asthma or chronic obstructive pulmonary disease (COPD). This study assessed the longitudinal validity, reliability of the change score and the interpretation of changes on the QoLRIQ in inpatient pulmonary rehabilitation, completed by 108 patients with moderate to severe asthma (39) or COPD (69). Domains and total score of the QoLRIQ changed significant (all p < 0.0002) with standardized response means from 0.46 to 0.90. All QoLRIQ-change scores were significantly correlated with self-rated change in health and in disease symptoms and with change in self-assessed health status (r from 0.2 to 0.61). There were several significant correlations between QoLRIQ-change scores and change in experienced invalidity, emotional well-being, anxiety, depressive symptoms and Rand-36-domains (r from 0.2 to 0.68). The intraclass correlation coefficient of change was 0.90. The size of a minimal important difference (MID), computed from a retrospective global rating of change by the patients and with the standard error of measurement, was 0.5 points on a 7-point response scale. Computation of the MID from retrospective assessment of change may not be valid because this change was significantly correlated to post-treatment health status and significantly higher than serial assessment of change. We conclude that the QoLRIQ is sensitive to change, longitudinally valid and reliable, with a MID of 0.5 points. These results enable the use of the QoLRIQ as an outcome measure in clinical trials with patients with moderate to severe asthma or COPD. The longitudinal measurement properties in less severe patients still need to be studied.

Adult↗
PubMed2003

Structural equation models for evaluating dynamic concepts within longitudinal twin analyses.

A great deal of prior research using structural equation models has focused on longitudinal analyses and biometric analyses. Some of this research has even considered the simultaneous analysis of both kinds of analytic problems. The key benefits of these kinds of analyses come from the estimation of novel parameters, such as the heritability of changes. This paper discusses some recent extensions of longitudinal multivariate models that can be informative within biometric designs. In the methods section we review a previous latent growth structural equation analysis of the New York Twin (NYT) longitudinal data (from McArdle et al., 1998). In the models section we recast this growth model in terms of latent difference scores, add several new dynamic components, including coupling parameters, and consider biometric components and examine model stability. In the results section we present new univariate and bivariate dynamic estimates and tests of various dynamic hypotheses for the NYT data, and we consider a few ways to interpret the age-related biometric components of these models. In the discussion we consider our limitations and present suggestions for future dynamic-genetic research.

Humans↗
PubMed2004

Leisure time physical activity and health-related quality of life: cross-sectional and longitudinal associations.

Studies that relate change in physical activity to change in health-related quality of life in the general population are needed to confirm associations suggested by cross-sectional studies. In the present study, cross-sectional as well as longitudinal associations between leisure time physical activity and health-related quality of life were studied in an apparently healthy population. The present study showed cross-sectional associations between at least moderately intense leisure time physical activity and general health perceptions, vitality, physical functioning and role limitations due to physical health problems. No associations were present for total leisure time physical activity. Change in leisure time physical activity was associated with change in social functioning in men as well as in women, irrespective of the intensity of physical activity. Only in men, change in total leisure time physical activity was associated with change in vitality and general mental health. In our study, cross-sectional associations were not confirmed by longitudinal analyses. Cross-sectional associations were mainly found for physical components of health-related quality of life, whereas longitudinal associations were predominantly observed for mental components of health-related quality of life. Confirmation of our results by those of other studies is needed in order to quantify health promotion messages.

Adult↗