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PubMed2004

Screw loosening for standard and wide diameter implants in partially edentulous cases: 3- to 7-year longitudinal data.

Screw loosening is considered to be a common problem with both screw-retained and cemented implant restorations. A wider abutment platform, as well as using a torque driver to tighten specifically designed screws may help prevent this loosening. However, there has been no clinical study evaluating either of these. To longitudinally compare the frequency of screw loosening in standard diameter, (3.75 and 4.0 mm) implant supported prostheses to that of wide diameter, (5.0 and 6.0 mm) implant supported prostheses that were hand tightened, and to evaluate whether using a torque driver would minimize or prevent this problem, if screw loosening occurred. A total of 213 dental implants in 106 patients were included in this prospective longitudinal study. Of the implants 68 were wide diameter and 145 were standard diameter implants. Wide diameter implants showed 5.8% screw loosening, while standard diameter implants showed 14.5% screw loosening after insertion with only hand torquing. When these loose screws were tightened with a torque driver, there was no more loosening of screws. Within the limitations of this study, the wide diameter implants tested showed less screw loosening than the standard diameter implants when hand torqued. Additionally, within the scope of our study, using a torque driver to tighten the screws with the recommended force prevented this loosening from reoccurring in all cases.

Adult↗
PubMed2002

Adolescent psychosocial maturity and alcohol use: quantitative and qualitative analysis of longitudinal data.

Based on a psyschosocial developmental framework, this study used a mixed model design, including both quantitative and qualitative methods, to examine the relationship between adolescents' psychosocial maturity and their alcohol use. A sample of 1,198 10th-grade students (51% female) was surveyed and followed up two years later. Both concurrent and longitudinal findings indicated that the more psychosocially mature adolescents were less likely to drink heavily than those who showed less maturity. At age 15 this relationship was even stronger for those whose peers also drank. Further, at age 17, this linear relationship was more pronounced for those who drank less heavily at age 15. Of the three psychosocial competencies examined, the construct of personal meaning was more strongly related to adolescent alcohol use than were the constructs of interpersonal understanding and interpersonal skills. To illustrate this construct, two of the adolescents were interviewed, a girl and a boy, individually at the end of both school years. Thematic and developmental analyses of the interviews revealed individual variations in how the adolescents made meaning of their drinking; these encourage speculations that go beyond the general pattern found in the study.

Adolescent↗
PubMed2004

Changes in sexual function in middle-aged and older men: longitudinal data from the Massachusetts Male Aging Study.

OBJECTIVES: To describe within-individual change in sexual function over a 9-year period and to determine whether the amount of change differs by age group. DESIGN: Cohort study; participants interviewed at baseline (1987-89) and follow-up (1995-97). SETTING: Population-based; communities surrounding Boston, Massachusetts. PARTICIPANTS: One thousand eighty-five men aged 40 to 70 at baseline (born between 1917 and 1947) with complete baseline and follow-up sexual function data. MEASUREMENTS: Within-person change (follow-up minus baseline) in the following sexual function variables: sexual intercourse, erection frequency, sexual desire, ejaculation with masturbation, satisfaction with sex, and difficulty with orgasm. RESULTS: Unadjusted analyses showed significant longitudinal changes over the 9-year period in all domains of sexual function except frequency of ejaculation with masturbation, which showed no change between baseline and follow-up. Adjusted for baseline sexual function, within-person change in all outcomes was strongly related to age, with decline in sexual function becoming more pronounced with increasing age. For example, over the 9-year study period, sexual intercourse or activity frequency decreased by less than once per month, two times per month, and three times per month in men in their 40s, 50s, and 60s, respectively. Number of erections per month declined by 3, 9, and 13 in men in their 40s, 50s, and 60s, respectively. CONCLUSION: This research fills a major gap in the literature by providing age-specific estimates of change in sexual functioning over a 9-year period in a cohort of unselected men.

Adult↗
PubMed2004

Longitudinal data for intrauterine levels of fetal IGF-I and IGF-II.

OBJECTIVE: An increasing body of evidence supports a major role for the insulin-like growth factors (IGFs) in the control of human fetal growth. Individual data at various times of pregnancy suggest that IGF-I and IGF-II levels remain stable up to the 33rd week of pregnancy. Thereafter, both increase to reach values 2-3 times higher at term. In order to provide an accurate reflection of fetal IGFs in utero, we sampled fetal blood from the umbilical cord by cordocentesis. METHODS: We measured IGF-I and IGF-II in 12 fetuses longitudinally for up to 5 times between the 21st week of gestation and delivery. RESULTS: All patients showed a progressive increase in IGF-I and IGF-II levels. Data determined during different time intervals (before 29th, 29th to 32nd, after 32nd week) were compared and the main increase was found after the 32nd week. The median for IGF-I before the 29th week was 33.5 ng/ml (range 19-40.5) and increased to 41 ng/ml (32-59) between the 29th to 32nd and further to 54.1 ng/ml (range 17-70) thereafter. During the same time interval, the median for IGF-II increased from 217 ng/ml (86-326) to 349 ng/ml (227-467). In 7 patients, cord blood after delivery was available. For IGF-II a further increase was consistently found after birth (from 282 ng/ml (175-511) to 393 ng/ml (297-513)), whereas only 2 fetuses showed an increase in IGF-I. CONCLUSION: We conclude that in human fetuses, IGF-I and IGF-II levels increase longitudinally throughout pregnancy. Therefore, they may become important markers of healthy fetal development.

Cordocentesis↗
PubMed1976

A regression model analysis of longitudinal dental caries data.

Longitudinal data on caries experience were derived from the reexamination and interview of a cohort of 306 subjects with an average follow-up period of 33 years after the baseline examination. Analysis of the data was accomplished by the use of contingency tables utilizing enumeration statistics compared with a multiple regression analysis. The analyses indicated a strong association of caries experience at one point in time with the caries experience of that same person earlier in life. The regression model approach offers adjustment of any given independent variable for the effect of all other independent variables, providing a powerful means of bias reduction. The model is also useful in separating out the specific effect of an independent variable over and above the contribution of other variables. The model used explained 35% of the variability in the DMFS scores recorded. Similar models could be useful adjuncts in the analyses of dental epidemiologic data.

Adolescent↗
PubMed2004

Simultaneous inference for longitudinal data with detection limits and covariates measured with errors, with application to AIDS studies.

In AIDS studies such as HIV viral dynamics, statistical inference is often complicated because the viral load measurements may be subject to left censoring due to a detection limit and time-varying covariates such as CD4 counts may be measured with substantial errors. Mixed-effects models are often used to model the response and the covariate processes in these studies. We propose a unified approach which addresses the censoring and measurement errors simultaneously. We estimate the model parameters by a Monte-Carlo EM algorithm via the Gibbs sampler. A simulation study is conducted to compare the proposed method with the usual two-step method and a naive method. We find that the proposed method produces approximately unbiased estimates with more reliable standard errors. A real data set from an AIDS study is analysed using the proposed method.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Is there a cognitive impairment in MND? A survey with longitudinal data.

Twenty-nine patients affected by motor neuron disease (MND) were investigated with the Raven Progressive Matrices, a test of logical non verbal intelligence, requiring neither motor nor verbal skills. The score distribution of the MND patients did not differ from that of 321 controls. Eleven of these patients were retested after a mean interval of 8.5 months. The resulting differences in the test scores showed that their intellectual performance had not worsened over time. Even allowing for the limitations posed by the use of a single test, these data add to the evidence against systematic cognitive involvement in MND.

Adult↗
PubMed1990

Development of a model longitudinal data base to measure outcomes and quality of care among persons with AIDS.

Not only are advances being made in delaying the virulent course of human immunodeficiency virus (HIV), but preventive measures are now available to eliminate or delay opportunistic infections related to HIV. Changes in the treatment of HIV-related diseases have shifted the focus from inpatient to community care. However, questions exist whether these gains in treatment outcomes will be available to all persons with HIV infection and whether uniform standards of care will be established and maintained among health care providers. In Maryland, and automated AIDS information system, HIVIS, consisting of administrative data bases and medical records systems, is used to measure health and social services costs and utilization and to assess their accessibility, quality and effectiveness. Since these data bases are available in other states, HIVIS serves as a model which may be implemented elsewhere for AIDS and other diseases.

Acquired Immunodeficiency Syndrome↗
PubMed2005

Assessing reliable and clinically significant change on Health of the Nation Outcome Scales: method for displaying longitudinal data.

OBJECTIVE: Many authors recommended that reliable and clinically significant change (RCSC) should be calculated when reporting results of interventions. To test the reliability of the Health of the Nation Outcome Scales (HoNOS) in identifying RCSC, we applied the Jacobson and Truax model to two HoNOS assessments in a large group of people evaluated in 10 community mental health services in Lombardy, Italy, in 2000. METHOD: The HoNOS was administered to 9817 patients; of these, 4759 (48%) were re-assessed. Reliable change (RC) was calculated using Cronbach's alpha (alpha), as a parameter of the reliability of the measure. Clinical significance cut-offs were calculated using a classification of severity based on HoNOS items. RESULTS: In the whole sample, the clinical improvement cut-off was 11 and the remission cut-off was 5. Considering the severe patients, the clinical improvement cut-off was 12. The RC index calculated on the whole group and on the subgroup of severe patients indicated that eight-point and seven-point changes, respectively, were needed to be confident that a real change had occurred. Longitudinal changes were depicted on two-dimensional graphs as examples of reporting RCSC on HoNOS total scores in a routine data collection: 91.6% of the whole sample (4361) was stable, 5.6% (269) improved and 1.8% (129) worsened. CONCLUSION: Our study proposes a methodological framework for computing RCSC normative data on a widely used outcome scale and for identifying different degrees of clinical change.

Follow-Up Studies↗
PubMed1994

A PC program for computing McMahan's tracking indices from one-sample longitudinal data sets.

Tracking refers to regular, predictable growth behavior. Most definitions of the term are related to the idea that tracking occurs to the extent that individuals' repeated measurements maintain their relative positions in the distribution of the measurement whose growth is being monitored as that distribution changes over time. In this paper we describe four indices of tracking, all due to McMahan (Biometrics, 37 (1981) 447-455), which may be used to measure the extent to which a given longitudinal sample exhibits this 'regular behavior,' and we provide a program, written in GAUSS386i, for performing the associated computations. An example is given, and the values of McMahan's indices are compared to several alternative measures of tracking.

Algorithms↗
PubMed1996

Latent transition analysis for longitudinal data.

Assessing outcome is a critical problem for the study of addictive behaviors. Traditional approaches often lack power and sensitivity. Latent Transition Analysis is an alternative procedure that is applicable to categorical latent variable models such as stage models. The method involves four different types of parameters, each of which may be relevant to different research questions. Two examples that employ the Stages of Change construct are used to illustrate the method. In the first example, three different models of longitudinal change are compared. In the second example, the effects of an expert system intervention for smoking is compared to a control condition. The method permits the investigation of a series of specific comparisons: (1) the effectiveness of the intervention for individuals in different stages can be assessed; (2) the effectiveness of the intervention can be evaluated for different time intervals; and (3) the effects of intervention on both progression through the stages and regression through the stages or relapse can be assessed. Other potential applications of the method are also discussed.

Alcoholism↗
PubMed2006

Human papillomavirus testing using hybrid capture II with SurePath collection: initial evaluation and longitudinal data provide clinical validation for this method.

BACKGROUND: Testing for human papillomavirus (HPV) is an integral part of equivocal cervical cytology triage. Clinical validation of non-FDA (Food and Drug Administration)-approved methods is therefore important because of the high volume of such tests and the implications for missed high-grade lesions if test performance is not optimal. METHODS: A preinitiation study and 17 months of follow-up data using Hybrid Capture II (HC II) HPV detection with SurePath (SP) sample collection were analyzed. Results of HPV tests on abnormal cytology samples were collected and compared with follow-up results. HPV-positive rates were determined in cases of low-grade squamous intraepithelial lesion (LSIL) and high-grade squamous intraepithelial lesion (HSIL), and follow-up rates of cervical intraepithelial neoplasia (CIN) were determined in HPV-positive and -negative cases of atypical squamous cells of unknown significance (ASC-US). Rates were compared with published data using FDA-validated methods. RESULTS: The preinitiation study showed the test method to be 100% sensitive for the detection of LSIL (20 cases) and HSIL (8). The ASC-US follow-up study (2319 cases with 625 having biopsy results) showed that the rate of CIN III+ in HPV +/- cases was 7.8%/1.4%, and of CIN II+ was 17.5%/4.3%, respectively. The positive predictive values/negative predictive values (PPV/NPVs) (CIN II+) for the test were 17.5%/95.7%, respectively. CONCLUSIONS: Published FDA-validated HPV testing follow-up data show that the expected rates of CIN III+ and CIN II+ in the HPV-negative ASC-US population are 1.4% and 5%, respectively, with PPV/NPVs (CIN II+) of 20%/99%, respectively. By comparison, the present data using HC II with SP show strong similarity, indicating clinical validity for the use of this method.

Carcinoma, Squamous Cell↗
PubMed2000

Maximum likelihood estimation for longitudinal data with truncated observations.

We obtain maximum likelihood estimates of the parameters when the observations on the response variable in a repeated measures design are truncated above a cutpoint. The maximum likelihood equations are solved iteratively using an EM-like procedure. It is observed that these estimates have smaller mean squared error than recently proposed iterative weighted least-squares estimates. The results are applied to data arising from a study of dioxin elimination in Air Force veterans. Published in 2000 by John Wiley & Sons, Ltd.

Aerospace Medicine↗
PubMed1987

Defining menopausal status: the impact of longitudinal data.

A population of 324 women who were over 45 and still menstruating were followed for a period of 3 yr. They were interviewed 6 times at 6-mth intervals. This paper presents data on the changes in menstrual status that occurred over the period of the study and relating these changes in menstruation to a woman's age and symptom experience.

Age Factors↗
PubMed1994

Analysis of longitudinal data with unequally spaced observations and time-dependent correlated errors.

A linear model for repeated measurements is proposed in which the correlation structure includes a transformation of the time scale. This transformation can produce nonstationary covariance structures within subjects with stationarity as a special case. Restricted maximum likelihood methods for parameter estimation are discussed. The method is applied to simulated data as well as speech recognition data from the Iowa Cochlear Implant Project. The growth curve for this audiologic performance measure is shown together with estimates of the standard errors of predictions at given months.

Audiology↗
PubMed1976

Estimation of growth velocities from individual longitudinal data.

Since the construction of growth velocity curves using the simple increment method (i.e., plotting the increments deltaxt vs, time, t) involves a number of methodological problems, when mathematical curves are fit, they are generally fit to the "distance traveled", plot (of xt vs. t) and the corresponding velocity curve is then obtained by differentiation. However, most of the traditional methods for accomplishing this (e.g., fitting the Gompertz or logistic curves) require that the course of growth be studied over a sufficiently long time period to allow accurate determinations of the upper and lower asymptotes of these S-shaped functions. This is not always feasible in practice: a case in point being the mixed-longitudinal Nijmegen Growth Study where each of the cohorts comprising the sample is followed for but a five-year period. In such situations, alternative approaches to the problem of constructing growth velocity curves may be of considerable practical as well as theoretical interest. One such approach is developed in this paper and its use is illustrated on some data collected as part of the Nijmegen Growth Study. These results are then compared with those obtained using the increment method on the same data.

Adolescent↗
PubMed2007

Regression models for mixed Poisson and continuous longitudinal data.

In this article we develop flexible regression models in two respects to evaluate the influence of the covariate variables on the mixed Poisson and continuous responses and to evaluate how the correlation between Poisson response and continuous response changes over time. A scenario for dealing with regression models of mixed continuous and Poisson responses when the heterogeneous variance and correlation changing over time exist is proposed. Our general approach is first to jointly build marginal model and to check whether the variance and correlation change over time via likelihood ratio test. If the variance and correlation change over time, we will do a suitable data transformation to properly evaluate the influence of the covariates on the mixed responses. The proposed methods are applied to the interstitial cystitis data base (ICDB) cohort study, and we find that the positive correlations significantly change over time, which suggests heterogeneous variances should not be ignored in modelling and inference.

China↗