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PubMed1997

Random effects probit and logistic regression models for three-level data.

In analysis of binary data from clustered and longitudinal studies, random effect models have been recently developed to accommodate two-level problems such as subjects nested within clusters or repeated classifications within subjects. Unfortunately, these models cannot be applied to three-level problems that occur frequently in practice. For example, multicenter longitudinal clinical trials involve repeated assessments within individuals and individuals are nested within study centers. This combination of clustered and longitudinal data represents the classic three-level problem in biometry. Similarly, in prevention studies, various educational programs designed to minimize risk taking behavior (e.g., smoking prevention and cessation) may be compared where randomization to various design conditions is at the level of the school and the intervention is performed at the level of the classroom. Previous statistical approaches to the three-level problem for binary response data have either ignored one level of nesting, treated it as a fixed effect, or used first- and second-order Taylor series expansions of the logarithm of the conditional likelihood to linearize these models and estimate model parameters using more conventional procedures for measurement data. Recent studies indicate that these approximate solutions exhibit considerable bias and provide little advantage over use of traditional logistic regression analysis ignoring the hierarchical structure. In this paper, we generalize earlier results for two-level random effects probit and logistic regression models to the three-level case. Parameter estimation is based on full-information maximum marginal likelihood estimation (MMLE) using numerical quadrature to approximate the multiple random effects. The model is illustrated using data from 135 classrooms from 28 schools on the effects of two smoking cessation interventions.

Clinical Trials as Topic↗

PubMed2001

Radiographic damage in rheumatoid arthritis correlates with functional disability but not direct medical costs.

OBJECTIVE: Few longitudinal data exist on the relationship between radiographic damage and self-reported functional disability and direct medical costs in rheumatoid arthritis (RA). We assessed these relationships. METHODS: One hundred thirty patients with RA (at time of the first available radiograph, mean age 56.6 yrs, 16.9% male, mean disease duration 16.8 yrs) were followed for up to 13.4 years. Semiannually, they reported on functional disability (0 = no difficulty, 3 = unable to do), global severity (0 = very well, 100 = very poor), pain (0 = no pain, 3 = severe pain), and health services utilization through completion of the Stanford Health Assessment Questionnaire (HAQ). Concurrent hand radiographs were scored for erosions and joint space narrowing using the Genant method and a single score summing both erosions and joint space narrowing for both hands was calculated (0 = no damage, 200 = maximum damage). The univariate association of functional disability, global severity, pain, or direct medical costs with concurrent radiographic damage was assessed through Spearman correlations and hierarchical regression models. The hierarchical models permit exploitation of the between-patient and within-patient variation present in our longitudinal data. RESULTS: At the time of the first available radiograph, mean (SD) levels of functional disability, global severity, and pain were 1.3 (0.7), 39.4 (21.0), and 1.1 (0.7), respectively. At entry into the study, the average radiograph score was 49.7 and upon leaving the study it was 66.9. Patients were followed an average of 6.7 years, with radiograph scores increasing at an average rate of 2.5 units/yr. The Spearman correlation [95% confidence interval (CI)] between average per-patient radiograph score and average per-patient HAQ disability index, average per-patient global severity, average per-patient pain score, and average per-patient direct medical costs was, respectively, 0.42 (0.26, 0.55), 0.23 (0.06, 0.39), 0.20 (0.03, 0.36), and 0.06 (-0.11, 0.23). The mean slope (95% CI) for disability on radiograph score was 0.0186 (0.0132, 0.0226), for severity on radiographs 0.1889 (0.1295, 0.2498), and for pain on radiographs 0.0057 (0.0027, 0.0084). As an example, over 10 years, a 25 unit (i.e., 50%) increase in radiograph scores would, on average, be associated with a 0.46 unit (i.e., 35%) increase in disability, a 4.72 unit (12%) increase in global severity score, and a 0.14 unit (13%) increase in pain, all expressed on the HAQ scales. There was little association between radiograph score and direct medical costs. CONCLUSION: A clinically meaningful association exists between radiographic damage and self-reported functional disability, suggesting that interventions that slow radiographic progression may improve the patient's health status. Such a relationship was not observed between radiographic damage and direct medical costs.

Aged↗

PubMed2006

The adolescent decline of NREM delta, an indicator of brain maturation, is linked to age and sex but not to pubertal stage.

Two dramatic phenomena of human adolescence are sexual maturation and a steep decline in the delta EEG of non-rapid eye movement (NREM) sleep. It has long been speculated that these developmental changes are causally related. Here, we present the first longitudinal data on this issue. Cohorts of 9- and 12-year-old children (n = 31, 38) were studied with in-home sleep EEG recordings at 6-mo intervals over 2 years. Pubertal (Tanner) stage, height, and weight were obtained at each time point. NREM delta power density (DPD) did not change significantly over ages 9-11 years, and its level did not differ in boys and girls. DPD declined by 25% between ages 12 and 14 years. This decline was parallel in the two sexes, but levels were lower in girls, suggesting that their DPD decline began earlier. Mixed effect analyses demonstrated that DPD was strongly related to age with Tanner stage, height, weight and body mass index controlled but that none of these measures of physical and sexual development was related to DPD with age controlled. NREM delta is the sleep EEG component homeostatically related to prior waking duration and the intensity of waking brain activity. We hypothesize that the DPD decline is caused by age-programmed synaptic pruning that decreases waking brain metabolic rate. This reduced rate would decrease the "substrate" for delta homeostasis. Whether or not this interpretation proves correct, these longitudinal data demonstrate that the delta decline in adolescence reflects brain processes that are not predicted by physical growth or sexual maturation.

Adolescent↗

PubMed2006

Autosomal dominant osteopetrosis: clinical severity and natural history of 94 subjects with a chloride channel 7 gene mutation.

CONTEXT: Autosomal dominant osteopetrosis (ADO) is a sclerosing bone disorder caused by heterozygous mutations in the chloride channel 7 (ClCN7) gene. The clinical manifestations of this disease have not been well characterized since the discovery of the genetic basis of ADO. OBJECTIVES: The primary objectives were to improve our understanding of ADO clinical characteristics and to study the natural history of the disease in the largest series of patients reported to date. DESIGN AND SETTING: This study was primarily a retrospective cross-sectional analysis of individuals with a ClCN7 mutation that was conducted over a 4-yr period at a tertiary referral center and through family reunions. Longitudinal data on a subset of subjects were also studied. PATIENTS AND INTERVENTIONS: We studied 311 subjects from 11 ADO families, including 62 individuals with ADO (patients with the classic clinical phenotype based on radiographs and/or biochemistry), 32 unaffected gene carriers (subjects with the gene mutation but no radiographic and/or biochemical phenotype), and 217 controls who did not harbor a ClCN7 gene mutation. Clinical data were collected through patient interviews and examinations, medical records, and/or self-reported responses on a questionnaire that was completed by all subjects. MAIN OUTCOME MEASURES: The prevalence of fracture, osteomyelitis, visual loss, and bone marrow failure was determined. Differences in clinical manifestations were analyzed according to affected vs. carrier status, age, and underlying genotype. RESULTS: Ninety-two percent of ADO subjects had at least one sequela of the disease. Gene carriers did not have an increased risk of disease manifestations, although they were found to have significant increases in bone mineral density (P < 0.05). Compared with controls, subjects with ADO had a significantly increased prevalence of fracture (84 vs. 36%; P < 0.0001) and osteomyelitis (16 vs. 0.9%; P < 0.0001). Severe fractures (defined as > or =10 fractures of any type and/or greater than one hip/femur fracture) were identified only in ADO subjects, and osteomyelitis typically occurred in the maxilla or mandible in older adults. Visual loss, which typically had its onset in childhood, and bone marrow failure occurred in 19 and 3% of ADO subjects, respectively. Adults were more likely to manifest an ADO clinical characteristic, but no definitive genotype-phenotype relationship could be concluded. Longitudinal data suggest that the ADO clinical phenotype worsens over time. CONCLUSIONS: ADO caused by mutations in the CLCN7 gene is a frequently symptomatic disease manifested by a high rate of fracture, osteomyelitis, visual loss, and occasional bone marrow failure. The sequelae of ADO, which can be identified as early as infancy, appear to worsen over time. Fracture is the most prevalent consequence of ADO, although other more severe manifestations of disease can occur and should not be confused with recessive forms of osteopetrosis, particularly when identified in early childhood.

Adolescent↗

PubMed1994

Client outcomes II: Longitudinal client data from the Colorado treatment outcome study.

The outcomes of a reform of the Denver mental health system, cosponsored by the state and the RWJF, are contrasted with changes in a comparison area of the state. The study examines the structural characteristics of the mental health system, staff attitudes and satisfaction, and client-reported services and outcome. Results indicate that, in Denver, structural changes, the introduction of new services, and an intervening financial crisis increased worker dissatisfaction. Client reports documented parallel changes in the following variables: continuity of care, unmet need for case management services, frequency of symptoms, and satisfaction with services. The reform had no impact, however, on most quality-of-life indicators. The possibly adverse consequences of centralizing the system and the indirect influences of system integration on quality of life are discussed.

Adult↗

PubMed1999

[Autonomic regulation in patients with panic attacks based on longitudinal study data on the variability of the heart rhythm].

During a repeated study in recumbent position as well as during 48-hour monitoring of the indices of variability of RR intervals of ECG (MDRR) in patients with panic attacks (PA) a stable dominance of VLF (0.07-0.01 Hz) and rigidity of the spectrum typical for patients with panic attacks (PA) in period between the attacks was found. Prevalence of fear emotions as well as accompanying hypothalamic insufficiency were also associated with a decrease of HF. In prodromic period, in attack and after it, there was no dynamics in the frequency of heart's contractions, but there was a sharp increase of MDRR. In prodromic period VLF and LF considerably increased, while HF decreased. In a moment of a panic attack LF and HF continued to increase, while VLF significantly lowered. Activation of vasomotor (LF), vagal (HF) and cerebral (VLF) mechanisms was maintained during 5 minutes of the study after PA completion with a clear predominance of LF component.

Adult↗

PubMed1993

Breast-feeding patterns in the Philippines: a prospective analysis.

Data from the Cebu Longitudinal Health and Nutrition Survey have been used to examine breast-feeding patterns in the Metropolitan Cebu region of the Philippines. The results show that there is extensive and early use of non-nutritive liquids, resulting in low levels of exclusive breast-feeding. The use of cross-sectional versus longitudinal data, the definition of exclusive breast-feeding, and movements in and out of the exclusively breast-fed category, are considered.

Adolescent↗

PubMed1992

The Zurich Study. XII. Sex differences in depression. Evidence from longitudinal epidemiological data.

A prospective study of depressive syndromes and diagnoses was performed among a young adult Swiss population with three interviews over 7 years. Different definitions of depressive states were used: on the one hand, depressive syndromes including mood disturbances of any severity, on the other, well-defined diagnoses of depression. Women were consistently overrepresented among subjects with depressive syndromes of some length and among those with DSM-III major depressive disorder. Both sexes appeared equally affected by brief recurrent depressions with work impairment. Between the ages of 20 and 30 years, men as a group in contradistinction to women showed depressive syndromes with decreasing frequency, whereas, for diagnoses, the sex rates remained quite constant. For identical syndromes, women at each interview reported a greater number of symptoms. DSM-III-R symptoms of melancholia were not reported more often by women than by men. When syndromes or diagnoses were controlled, women and men suffered to an equal rate from subjective impairment at work. Women's syndromes were more recurrent. Among women, a diagnosis of depression was more often associated with disturbances of appetite and with phobias than among men. The importance of differential recall for sex differences in prevalence is discussed. Sex differences may have different weight and different causes with regard to depressive syndromes and to a diagnosis of depression.

Adult↗

PubMed2002

Metric properties of the appropriateness evaluation protocol and predictors of inappropriate hospital use in Germany: an approach using longitudinal patient data.

BACKGROUND: The German health care system, renowned for its unrestricted access, high quality care, and comprehensive coverage, is challenged by increasing health care costs. This has been attributed partly to inefficiencies in the in-patient sector, but has been studied little. Attempts at quality improvement need to relate costs to outcomes. Until now, there has been no standardized methodology to evaluate the appropriateness of hospital care. OBJECTIVE: To develop and evaluate the metric properties of a method to assess inappropriate hospital care in Germany based on a widely used measure, the Appropriateness Evaluation Protocol (AEP). METHODS: The original AEP was translated and adapted to reflect differences in the provision of health care in Germany. Psychometric testing was performed in a stratified sample of all patients admitted to the Departments of Medicine and Surgery of a 400-bed teaching hospital during 1 year. Three board-certified physicians participated in each department to evaluate intra-rater reliability, while two additional independent physicians judged inter-rater reliability. RESULTS: Inter-rater agreement for the evaluation of hospital days among surgical patients was 84% (80-87%), with an average kappa value of 0.58 (0.48-0.68). Corresponding figures for patients in medicine were 76% (73-80%) with a K value of 0.42 (0.34-0.42). Inter-rater agreement for hospital admissions and K was 74% (62-86%) and 0.44 (0.21-0.67) in surgery, and 92% (85-100%) and 0.31 (0-0.80) in medicine, respectively. Thirty-three per cent of all admissions and 28% of consecutive hospital days were judged inappropriate in surgery; among medicine patients, reviewers found 6% of admissions and 33% of hospital days inappropriate. Time since admission was the strongest predictor of inappropriate hospital use adjusted for length of stay, comorbidity, age, and gender.

Adult↗

PubMedDate not supplied

Health insurance among children: the role of expanded Medicaid coverage.

This study uses data from the National Longitudinal Survey of Youth to track the health coverage of parents in the year before and the year in which their children enroll in Medicaid. Use of such longitudinal data, compared to cross-sectional data, provides more insight into the dynamics of health insurance coverage and expansions in Medicaid. Using these data, we find that approximately 16% of newly enrolled Medicaid children likely had access to private insurance through a parent. Moreover, most of the children enrolling in Medicaid were previously uninsured. We find little substitution of private for public health insurance among families living at or near the federal poverty line.

Child↗

PubMed2006

How did welfare reform affect the health insurance coverage of women and children?

OBJECTIVE: To measure the change in U.S. women and children's health insurance coverage as a result of welfare reform (i.e. the creation of Temporary Assistance for Needy Families or TANF) in 1996. DATA SOURCE: 1992-1999 longitudinal data from the Survey of Income and Program Participation (SIPP) merged with data on the timing of state implementation of welfare reform after 1996. Two key advantages of the SIPP data are that they permit matching type of insurance coverage to the welfare policy environment in each state in each month, and permit controlling for individual-level fixed effects. STUDY DESIGN: We measure how much insurance coverage changed after welfare reform using a difference in differences method that eliminates the influence of time-invariant unobserved individual heterogeneity and of statewide trends in insurance coverage. Models also control for individual, state, and year fixed effects, individual-level characteristics such as education, age, and number of children, plus state-level variables such as real per capita income, real minimum wage, and Medicaid eligibility. DATA COLLECTION/EXTRACTION METHODS: We limit our analysis to the SIPP data specific to the month just completed prior to the interview; as a result, we have up to twelve observations for each individual in the SIPP. This paper uses pooled data from the 1992-1996 panels of the SIPP covering the period 1992-1999. Publicly available state identifiers permit the merger of state policies and macroeconomic variables with the SIPP. PRINCIPAL FINDINGS: TANF implementation is associated with an 8.1 percent increase in the probability that a welfare-eligible woman was uninsured. Welfare reform had less of an impact on the health insurance coverage of children. For example, TANF implementation was associated with a 3.0 percent increase in the probability that a welfare-eligible child lacked health insurance. CONCLUSIONS: An unintended consequence of welfare reform was to adversely impact the health insurance coverage of economically vulnerable women and children, and that this impact was several times larger than the previous literature implies.

Adolescent↗

PubMedDate not supplied

[Influence of the aging process on body composition of the aged: the SENECA study in Spain].

The maintenance of an adequate proportion of muscular mass in aging, is critical for the quality of life of elderly people. In the face of the lack of longitudinal data, the semi-longitudinal SENECA (Survey in Europe on Nutrition and the Elderly, a Concerted Action) study was proposed, with the aim, among others, of analyzing the influence of the aging process on the body composition. In this study, the results are presented which correspond to the changes in body composition seen between the baseline study and the follow up period (1989-1993), in the participating Spanish population, which was randomly selected, and whose ages were between 70 and 80 years. There is also an analysis of the relation existing in 1993, between different anthropometric measurements and the functionality evaluated objectively by means of the physical and functional capacity test (PPT). Using a standardized methodology, the following were measured: size, breadth, weight, biceps and triceps fold, and the circumference of the waist, hips, and the upper arm. Based on these measurements, we calculated the body mass index (BMI), the waist/hip ratio, the muscular circumference of the arm, the fat mass, and the fat free mass. The longitudinal analysis between 1989-1993 showed a decrease for both sexes, in weight (-3.5 +/- 5.0 in men, and -3.4 +/- 4.0 kg in women: p < 0.001) and body circumferences; and also, in women, in the size and the triceps fold (-0.63 +/- 1.42 cm, p < 0.01, and -3.6 +/- 4.6 mm, p < 0.001, respectively). Consequently, the BMI (-1.4 +/- 1.8 for men and -1.4 +/- 1.8 kg/m2 in women, p < 0.01) decreased, while the waist/hip ratio did not change. A reduction of the fat free mass of -1.6 +/- 2.1 kg (p < 0.01) in men and -1.2 +/- 1.3 kg in women (p < 0.001), was observed, as well as a reduction of the body fat of -1.8 +/- 2.0% and -1.7 +/- 2.6% (p < 0.001), respectively. On the other hand, analyzing the anthropometric measurements of the follow up study, a positive association was detected for men, between the waist and hip measurements and the functionality measured by the PPT.

Aged↗

PubMed2005

Do seniors understand their risk of moving to a nursing home?

OBJECTIVE: To determine whether seniors understand their risk of moving to a nursing home. Data Sources. We used longitudinal data from the Asset and Health Dynamics Among the Oldest Old (AHEAD) database. AHEAD is a nationally representative survey (n=8,203) of community dwellers aged 70+ years and their spouses. STUDY DESIGN: We followed respondents for 5 years from the date of the first interview fielded in 1993. Our primary dependent variable was whether respondents moved to a nursing home within 5 years of baseline; self-assessed probability of moving to a nursing home within 5 years, also assessed at baseline, was the primary explanatory variable. PRINCIPAL FINDINGS: We found that seniors who believed they were more likely to move to a nursing home within 5 years were indeed more likely to do so, and that most elders overestimated their likelihood of moving to a nursing home. CONCLUSIONS: Low rates of private long-term care insurance are not plausibly a result of seniors underestimating their personal risk of moving to a nursing home; such an assumption is inherent in many strategies to plan for the future long-term care needs of the baby boom generation.

Aged↗

PubMed1998

Approaches to population kinetic analysis with application to metabolic studies.

Population kinetic analysis is the methodology traditionally used to quantify inter-subject variability in pharmacokinetic studies. In the statistics literature, it is also called analysis of repeated measurement data or analysis of longitudinal data. In this work, we will state the population kinetics problem and give some historical background to its significance. Then we will describe and apply to case studies in intermediary metabolism various two-stage and other parametric methods for nonlinear mixed effects models. We will then briefly review the software available for population kinetic analysis.

Computer Simulation↗

PubMed2006

Pubertal onset and sexual orientation in an adolescent national probability sample.

Using 6-year longitudinal data from the National Longitudinal Survey of Adolescent Health (Add Health) and multiple measures of puberty as it occurs and of sexual orientation (romantic attraction, sexual identity), the present study attempted to replicate previous research which reported that homosexuals and heterosexuals differed in their age of pubertal onset. The study hypotheses were not confirmed for either males or females: on most pubertal measures, same-sex oriented groupings did not differ from heterosexuals. The only significant findings regarding homosexual males indicated that they were more likely to report having a later rather than an earlier onset of puberty, and the significant findings regarding homosexual females were contradictory--they tended to have an earlier onset of puberty. These findings are attributed to methodological improvements in the present study that reduced retrospective bias, used multiple indicators of sexual orientation and puberty timing, and assessed less eroticized measures of puberty.

Adolescent↗

PubMed2006

Evaluation of selected laboratory components of a comprehensive periodic health evaluation for veterans with spinal cord injury and disorders.

OBJECTIVE: To evaluate selected laboratory components of a comprehensive periodic health evaluation program for patients with spinal cord injury and disorders (SCI/D). DESIGN: A retrospective study. SETTING: A Department of Veterans Affairs spinal cord injury center. PARTICIPANTS: Community-dwelling male veterans with SCI/D (N=350). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Proportion of laboratory tests that resulted in new diagnoses (diagnostic yield) and proportion of laboratory tests that resulted in changes in management (therapeutic yield). RESULTS: Although abnormality rates for many routine laboratory tests were high (up to 31.5%), diagnostic and therapeutic yields were low (<1.5%), with the exception of glucose (therapeutic yield, 3.4%) and lipid tests (up to a 4.1% diagnostic and 15.2% therapeutic yield). CONCLUSIONS: Our data revealed that diagnostic and therapeutic yields for many laboratory components of the annual PHE program for veterans with SCI/D were low, consistent with findings in the general ambulatory population. Further data collection, particularly prospective longitudinal data, may help optimize the selection and frequency of laboratory tests performed as part of this program.

Adult↗

PubMed2005

Cognitive characteristics of patients with borderline personality disorder: development and validation of a self-report inventory.

Based on cognitive concepts of personality disorders as well as on the bio-social model of borderline personality disorder (BPD), a 34-item instrument, the questionnaire of thoughts and feelings (QTF) was developed for the assessment of feelings, strategic cognitions, and assumptions characteristic for BPD. In different studies, item- and factor analyses were conducted with a dataset of N=646 clinical and non-clinical participants. Cross-sectional data as well as longitudinal data are available including several other measures on personality and personality disorders: DSM-IV SCID II dimensional score, a personality inventory (PSSI), the German version of the personality disorder beliefs questionnaire (PBQ), as well as overall severity of symptoms (GSI) of the SCL-90-R. Internal consistency of the scale is excellent, Cronbach's alpha=0.91. One-week test-retest reliability was also high r(tt)=0.81. Good convergent and discriminant validity was obtained for correlation with SCID dimensional scores and discrimination of BDP patients and other clinical and non-clinical groups. A comparison of scores in a sample of 26 patients with BPD during crisis intervention and 8 months later indicated the sensitivity of the QTF to measure change over time. Overall, the questionnaire appears to be a methodologically sound measure, valuable for research purposes as well as in clinical practice.

Adult↗

PubMed2000

Precursive depression among HIV infected AIDS caregivers over time.

This study examines depression among HIV infected AIDS caregivers, documenting and explaining variation in health within a stress proliferation framework. Longitudinal data for 376 HIV- and HIV+ caregiving men who self-identify as gay are analyzed to establish how changes in depression are influenced by care-related stressors and by being a member of the gay, HIV-affected community. This research identifies the mechanisms by which the caregiver stress process unfolds distinctively among caregivers with AIDS-related health problems, in comparison to HIV- caregivers. Three waves of data are analyzed using longitudinal multiple regression models. Among HIV infected caregivers, mental health is affected by deteriorating health, perceptions of AIDS alienation/stigma, internalized homophobia, role overload, and financial worry. For both groups, depression is a function of social constriction and AIDS-related bereavement. The precursive nature of caregiving among these HIV infected men may magnify the stress of being in poor health, gay, and stigmatized.

Adult↗