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PubMed1999

Adult craniocervical and pharyngeal changes--a longitudinal cephalometric study between 22 and 42 years of age. Part II: Morphological uvulo-glossopharyngeal changes.

The purpose of this study was to investigate, by cephalometric means, longitudinal alterations in uvulo-glossopharyngeal morphology in adult males and females, at three different ages with 10-year intervals, and to compare the changes between the two genders. The material consisted of three series of cephalograms of 26 males and 24 females, with approximately a 10-year interval between each series. Alterations with age in males and females included: 1 An increase in the length, thickness, and sagittal area of the soft palate, with a more upright position for both genders. 2 A more upright tongue position and caudally-extended tongue mass for both sexes was found, and the sagittal area of the tongue was significantly increased only in males. 3 There was a decrease in the sagittal dimension of the oropharynx, and at the minimal distance between the base of the tongue and the posterior pharyngeal wall in both males and females. The overall significant inter-sex differences, over a 20-year period, were that males showed a more upright tongue position and more caudally-extended tongue mass, a greater reduction in sagittal dimension of the minimal pharyngeal airway space, a greater increase in the sagittal area of the soft palate, and an increase in the tongue area.

Adult↗
PubMed1999

Adult craniocervical and pharyngeal changes--a longitudinal cephalometric study between 22 and 42 years of age. Part I: Morphological craniocervical and hyoid bone changes.

The purpose of this study was to investigate longitudinally, by cephalometric means, alterations in craniocervical morphology and hyoid bone position in adult males and females, in three different age groups at 10-year intervals, and to compare the changes between the two genders. The material consisted of three series of cephalograms of 26 males and 24 females with approximately a 10-year interval between each series. Alterations with increasing age in males and females included: 1 An increase in anterior and posterior facial height in both genders, a reduction in mandibular prognathism, and an increase in the mandibular plane angle in females only. 2 The hyoid bone assumed a more inferior position in relation to different skeletal structures for both sexes. 3 Head posture alterations were similar for the male and female group over time. The overall significant inter-sex changes over a 20-year period were a reduction in mandibular prognathism, an increase in the mandibular plane angle in females, and a more inferior position of the hyoid bone in males.

Adult↗
PubMedDate not supplied

Some considerations in the analysis of rates of change in longitudinal studies.

This paper discusses and compares several estimators of mean rate of change in unbalanced longitudinal data based on a model with randomly distributed regression coefficients across individuals. The estimators are unweighted and weighted means of these coefficients. The paper also evaluates commonly used variance estimates corresponding to the estimators. Results show that in situations of very slight imbalance, the choice of method is not critical. When imbalance is substantial, however, one should weight the regression coefficients by their estimated precision. An example using data from a nutritional study on premature neonates illustrates some issues encountered in the analysis of longitudinal clinical data sets.

Humans↗
PubMed2001

Assessing change with longitudinal and clustered binary data.

Investigators often gather repeated measures on study subjects to directly measure how a subject's response changes with changes in explanatory variables. This paper focuses on several statistical issues related to assessing change with longitudinal and clustered binary data. Many popular approaches for analyzing repeated binary outcomes measure cross-sectional or between-subject, rather than within-subject, effects of covariates. The class of models known as cluster specific measures within-subject effects of covariates on responses but are subject to additional statistical complications. It is useful to decompose covariates into between- and within-cluster components. This paper describes several approaches that yield consistent estimates of the within-subject covariate effects of interest. Example data from three studies illustrate the results.

Humans↗
PubMed1999

Longitudinal cephalometric changes in the maxilla, mandible and maxillary-mandibular relationship between 10 and 14 years of age.

In the present study, longitudinal growth changes in the maxilla, mandible, and maxillary-mandibular relationship occurring between the ages of 10 and 14 years were evaluated in 19 female and 15 male subjects. All subjects had a clinically-acceptable occlusion, a normal growth pattern, and none had undergone orthodontic treatment. Serial cephalometric radiographs were taken at the ages of 10, 11, 12, and 14 years. The effects of age and sex on the sagittal growth of the jaws were studied by means of variance analysis. The results show that A-Ptm, B-Ptm, Pg-Ptm, A'-Ptm, B'-Ptm, and S-N-Pg measurements were affected by age, and the measurements A-Ptm, A'-Ptm, Wits and ANB by sex. Duncan's multiple range test was applied to those measurements where F values were found to be statistically significant. As a result, it was observed that the greatest growth changes occurred between 12 and 14 years old.

Adolescent↗
PubMed2002

Longitudinal cephalometric changes in incisor position, overjet, and overbite between 10 and 14 years of age.

The purpose of this study was to evaluate the longitudinal growth changes in the incisor position, overjet, and overbite between 10 and 14 years of age. Serial cephalometric radiographs of 63 subjects (31 boys and 32 girls) were taken at the ages of 10, 11, 12, and 14. The effects of age and gender on the incisor positions, overjet, and overbite were investigated by means of variance analysis and least square difference (LSD) tests. The results show that the measurements of overbite, upper incisor-NA (mm), lower incisor-NB (mm), upper incisor-NA (angle), and the interincisal angle were affected by age. The results also show that the measurements of overbite, upper incisor-NA (mm), upper incisor-NA (angle) and upper incisor-SN (angle) were affected by gender.

Adolescent↗
PubMed1999

Longitudinal peri-implant clinical responses in anterior mandibles of female patients: a preliminary report.

STATEMENT OF PROBLEM: There is a need for specific documentation that successful osseointegration related to Brânemark implants can be maintained, despite an apparent clinically vulnerable peri-implant soft tissue status. PURPOSE: This study monitored longitudinal peri-implant clinical responses in the mandible and sought to question whether a relatively deep mucogingival pocket will give rise to a greater loss of peri-implant bone than a shallow pocket. METHODS AND MATERIAL: Subjects, 8 women patients (mean age 62 years), were treated with Brânemark mandibular osseointegrated implant-supported prostheses. Four of these subjects had limited (average <3.5 mm) and 4 had unlimited (average > or =3.5 mm) peri-implant pocket probing depths and constituted the control and test subgroups, respectively. Longitudinal changes in peri-implant PAL and radiographic bone support were assessed. RESULTS: Overall probing attachment levels (PALs) of the peri-implant mucogingival complex showed little change. The PAL loss was only minimally significant within the control subjects, and not significant for test subjects. The difference in these mucogingival responses between test and control subjects was significant (P = .04). There was no significant overall longitudinal change in peri-implant bone levels. The longitudinal change of peri-implant bone level was not significant within or between the control and test subjects.

Aged↗
PubMed2001

Impact of missing data due to drop-outs on estimators for rates of change in longitudinal studies: a simulation study.

Many cohort studies and clinical trials are designed to compare rates of change over time in one or more disease markers in several groups. One major problem in such longitudinal studies is missing data due to patient drop-out. The bias and efficiency of six different methods to estimate rates of changes in longitudinal studies with incomplete observations were compared: generalized estimating equation estimates (GEE) proposed by Liang and Zeger (1986); unweighted average of ordinary least squares (OLSE) of individual rates of change (UWLS); weighted average of OLSE (WLS); conditional linear model estimates (CLE), a covariate type estimates proposed by Wu and Bailey (1989); random effect (RE), and joint multivariate RE (JMRE) estimates. The latter method combines a linear RE model for the underlying pattern of the marker with a log-normal survival model for informative drop-out process. The performance of these methods in the presence of missing data completely at random (MCAR), at random (MAR) and non-ignorable (NIM) were compared in simulation studies. Data for the disease marker were generated under the linear random effects model with parameter values derived from realistic examples in HIV infection. Rates of drop-out, assumed to increase over time, were allowed to be independent of marker values or to depend either only on previous marker values or on both previous and current marker values. Under MACR all six methods yielded unbiased estimates of both group mean rates and between-group difference. However, the cross-sectional view of the data in the GEE method resulted in seriously biased estimates under MAR and NIM drop-out process. The bias in the estimates ranged from 30 per cent to 50 per cent. The degree of bias in the GEE estimates increases with the severity of non-randomness and with the proportion of MAR data. Under MCAR and MAR all the other five methods performed relatively well. RE and JMRE estimates were more efficient(that is, had smaller variance) than UWLS, WLS and CL estimates. Under NIM, WLS and particularly RE estimates tended to underestimate the average rate of marker change (bias approximately 10 per cent). Under NIM, UWLS, CL and JMRE performed better in terms of bias (3-5 per cent) with the JMRE giving the most efficient estimates. Given that markers are key variables related to disease progression, missing marker data are likely to be at least MAR. Thus, the GEE method may not be appropriate for analysing such longitudinal marker data. The potential biases due to incomplete data require greater recognition in reports of longitudinal studies. Sensitivity analyses to assess the effect of drop-outs on inferences about the target parameters are important.

Adolescent↗
PubMed1982

Pulmonary function in firefighters: a six-year follow-up in the Boston Fire Department.

Tests of ventilatory capacity, objective cough, and standardized respiratory questionnaires were used in a prospective study to measure the effect of firefighting on pulmonary function in a cohort of 951 white Boston firefighters between 1970-1976. During the six years of follow-up, the mean annual decrements in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were 36 and 29 ml per year, respectively. At the end of the study in 1976, the mean FEV1 for this group was 98.3% of the level predicted for healthy nonsmoking adults, while the FVC was 97.8%. Current cigarette smoking was associated with an increased prevalence of bronchitis, a loose cough, reduced levels of FEV1 and FVC, and increased longitudinal changes in FEV1 and FVC. The longitudinal changes and current levels of FEV1 and FVC were not correlated with any index of firefighting exposure in active firefighters. Increased use of protective respiratory apparatus and previously described selection effects within the Boston Fire Department appear to be protecting this group of firefighters from long-term effects of smoke exposure as measured by these techniques.

Adult↗
PubMed2026

A multi-ancestry polygenic risk score for body mass index predicts longitudinal weight change.

BACKGROUND: Identifying individuals at risk for future weight gain is challenging, partly because associations with traditional clinical risk factors may be biased by confounding and reverse causation. Polygenic risk scores (PRS) provide a stable, lifelong measure of genetic predisposition to obesity. However, existing PRS have not been evaluated for their association with longitudinal weight change in adulthood and often lack generalizability across diverse genetic ancestry groups. METHODS: We conducted ancestry-specific genome-wide association study meta-analyses of body mass index (BMI) in populations of European, African or African American, Admixed American, East Asian, and South Asian ancestries and developed ancestry-specific PRS. A multi-ancestry polygenic risk score (MAPRS) was trained using ancestry-specific PRS in a model selection dataset (N&#x2009;=&#x2009;39,685) from the All of Us Research Program (AoU). We evaluated the MAPRS in an independent AoU model evaluation dataset (N&#x2009;=&#x2009;158,743) for BMI prediction and in a separate AoU test dataset (N&#x2009;=&#x2009;78,219) with repeated measurements over 1.5-2.5 years for weight change prediction. The outcomes included change in BMI and&#x2009;&#x2265;&#x2009;10% or&#x2009;&#x2265;&#x2009;5% total body weight (TBW) gain. We further examined the relationship between MAPRS and 12 clinical risk factors commonly comorbid with obesity in relation to weight change. RESULTS: The MAPRS captured 7.05% of the variance in measured BMI in the AoU model evaluation dataset and demonstrated improved generalizability across all non-European genetic ancestry groups. In the AoU test dataset, conditioned on baseline BMI at the second-to-last measurement, a one SD increase in MAPRS was associated with a 0.16 kg/m2 increase in future BMI (standard error&#x2009;=&#x2009;0.012 kg/m2; p-value&#x2009;=&#x2009;2.2&#x2009;&#xd7;&#x2009;10-39), 1.27-fold increased odds of experiencing&#x2009;&#x2265;&#x2009;10% TBW gain (95% CI: 1.24-1.31; p-value&#x2009;=&#x2009;1.4&#x2009;&#xd7;&#x2009;10-55), and 1.15-fold increased odds of experiencing&#x2009;&#x2265;&#x2009;5% TBW gain (95% CI: 1.13-1.18; p-value&#x2009;=&#x2009;2.8&#x2009;&#xd7;&#x2009;10-39). These associations were observed across all genetic ancestry groups and remained highly consistent after adjustment for any clinical risk factor. In contrast, most clinical risk factors demonstrated inconsistent or weaker associations with weight change outcomes. CONCLUSIONS: We developed an MAPRS for BMI that represents a robust and generalizable risk factor for longitudinal weight gain in adulthood, providing a foundation for genetically informed risk stratification and earlier, more targeted obesity prevention strategies.

Humans↗
PubMed2002

Relationships between clinical attachment level and spine and hip bone mineral density: data from healthy postmenopausal women.

BACKGROUND: There are physiological reasons to expect an association between bone mineral density of the spine and hip and attachment loss. To this point, however, most studies have found no correlation. METHODS: The 135 patients in this report were part of a randomized controlled trial of estrogen replacement. All patients were in good oral health at entry and received annual oral prophylaxis as part of the study. Standard probing measurements were made with a pressure sensitive probe at 6 sites on each tooth. Bone mineral density was measured with dual-energy x-ray absorbtiometry at the lumbar spine (anterior-posterior and lateral) and proximal femur (neck, trochanter, intertrochanter, Ward's triangle, and total area). These procedures were performed at baseline and at annual intervals for 3 years. RESULTS: Correlations between cross-sectional measurements of clinical attachment level and bone mineral density were very weak, and did not approach statistical significance (-0.06 < or =r < or =0.10, 0.15 < or =P < or =0.75). A few somewhat stronger correlations were found between longitudinal changes in bone mineral density and attachment (-0.20 < or = r < or =-0.02, 0.02 < or = P < or =0.81). Although the correlations in the longitudinal changes were weak, they were consistently in the direction of greater bone mineral density being associated with less attachment loss. CONCLUSIONS: There is no clear association between clinical attachment level and bone mineral density of the lumbar spine and proximal femur, whether examined on a cross-sectional or longitudinal basis. Patterns in the data suggest there may be a weak association in the longitudinal changes.

Absorptiometry, Photon↗
PubMed2004

Multivariate longitudinal models for complex change processes.

Longitudinal studies offer us an opportunity to develop detailed descriptions of the process of growth and development or of the course of progression of chronic diseases. Most longitudinal analyses focus on characterizing change over time in a single outcome variable and identifying predictors of growth or decline. Both growth and degenerative diseases, however, are complex processes with multiple markers of change, so that it may be important to model more than one outcome measure and to understand their relationship over time. We consider random effects models for the association between the trajectories of two outcomes over time, and then compare their properties to approaches based on separate ordinary least-squares estimates of change. We then illustrate with an example from the Religious Orders Study, a longitudinal cohort study of more than 900 members of Catholic religious orders who have had up to eight annual clinical examinations.

Aged↗
PubMed1999

The effect of diabetes mellitus on histopathological changes in the denture-supporting tissues under continuous mechanical pressure in rat.

The histopathological changes in denture-supporting tissues of streptozotocin-induced diabetes mellitus rat were studied in relation to continuous mechanical pressure exerted through an experimental denture base. The experimental dentures were designed to load continuous mechanical pressures (3.4, 1.5 or 0.5 kPa) to the hard palate of the molar region of a rat. From the results of this study, the following conclusions were drawn: the streptozotocin-induced diabetic condition (1) tended to prolong the appearance period of a shortened epithelial ridge, and weakened the phenomenon, (2) reduced the appearance period and severity of the compression of epithelium, (3) delayed the time of manifestation of the proliferative change in the recovery process of the shortened epithelial ridge, and weakened the phenomenon, (4) prolonged the appearance period of the compressed lamina propria mucosae, and enhanced the phenomenon, (5) reduced the number of osteoclasts, (6) lowered the threshold for induction of the osteoclastic bone resorption to between 1.5 and 0.5 kPa, (7) inhibited the appearance of osteoblast which follows the disappearance of osteoclasts, (8) did not induce any inflammatory change, and (9) tended to enhance the longitudinal change of the continuous mechanical pressure. The histopathological changes in the denture-supporting tissues of the streptozotocin-induced diabetes mellitus rat related highly to the longitudinal change of the continuous mechanical pressure exerted through the denture base. From the results of this study, it was suggested that the streptozotocin-induced diabetic condition lowers the tolerance of the denture-supporting tissues to continuous mechanical pressure.

Animals↗
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↗
PubMed2005

apoE4 allele and the natural history of cardiovascular risk factors.

The aims of the present study were to compare the longitudinal changes in traditional cardiovascular (CV) risk factors (blood pressure, BMI, total and HDL-cholesterol, triglycerides, and blood glucose) in men with and without the apolipoprotein (apo)E4 allele. Three hundred six men from the Baltimore Longitudinal Study of Aging, ranging in age from 20 to 92 yr, were studied. Repeated measurements of CV risk factors were performed over a median follow-up time of 7 yr (maximum 14.3 yr) for men. Longitudinal changes in these CV risk factors were analyzed by linear mixed-effects models. The prevalence of the apoE4 allele was 25.5%. apoE4 was independently associated with accelerated changes over time in fasting plasma glucose (+9.5% vs. no change in those without apoE4 in the 6th age-decade over 10 yr). No significant effect of apoE4 on longitudinal changes in total or HDL-cholesterol, triglycerides, or blood pressures was observed. In conclusion, apoE4 influences fasting plasma glucose and its changes over time. This could explain, in part, the increased CV risk associated with the apoE4 genotype observed in men.

Adult↗
PubMed1988

[Decrement of respiratory function indices in a case series of workers exposed to cement dust: a longitudinal study].

Longitudinal changes in some respiratory parameters (FEV1 and VC) have been examined in a sample of cement workers (163 male subjects differently exposed to cement dusts); the subjects have been surveyed over a period of 10 years performing yearly spirometric tests (Vital capacity--VC and Forced Expiratory Volume in 1 second--FEV1 measurements). Three possible risk indicators have been considered: occupational exposure, smoking habit and age. 65.6% and 60.7% of the cases showed significant individual annual decreases of VC and FEV1 throughout the time of follow up. According to our results the occupational risk indicator has not significantly influenced the normal trend of decreases of the respiratory parameters; instead age brings about an increase of longitudinal changes of VC and smoke habit an increase of longitudinal changes of FEV1, (but only in the younger group, people less than forty years old). 16 subjects characterized by abnormal losses (more than 100 ml/year) have been selected as "VC-FEV1, losers".

Adult↗
PubMed2001

On the evaluation of drug benefits policy changes with longitudinal claims data: the policy maker's versus the clinician's perspective.

Cost containment in pharmaceutical-benefit plans are often controversially debated for their potential of unintended consequences on health and overall expenditures. Thorough evaluations are needed but hypotheses and design considerations are complex. Our objective is to provide a structured framework for the evaluation of drug-benefit changes using longitudinal claims data. Differential cost sharing (DCS) will serve as a recent example. Benefit-plan managers are mainly interested in the overall performance of their plan. In a policy model, any observed policy-related effects may be compared with what would have happened had the intervention not been implemented by extrapolating the pre-policy trend from the same patients. These estimates will reflect the global consequences of the policy maker's decision. However, such estimates represent summary effects of benefits and harms, separately identifiable in those complying with the intended policy and those not complying. Results from a policy model apply only to a specific policy implementation and tend to underestimate effects when non-compliance is high. Clinical-decision makers and patients, by contrast, are interested in the consequences of patients' actual compliance to the policy. A clinical model assesses the effects of DCS depending on the actual treatment in contrast to the treatment intended by the policy. However, this model must sometimes make, unprovable assumptions about the appropriate control of selection factors. In conclusion, both policy and clinical models should be tested with a clear understanding of their perspectives, hypotheses, and interpretations, using quasi-experimental time-series designs to evaluate the effects of drug cost-containment policies.

Attitude of Health Personnel↗