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PubMed2006

I. Longitudinal changes in aging brain function.

Changes in brain activity over time were evaluated in a group of older adults in the Baltimore Longitudinal Study of Aging who maintained good physical and cognitive health. Participants underwent PET scans during rest and delayed verbal and figural recognition memory performance at year 1 baseline and at year 9. While memory performance remained stable over the 8 years, longitudinal changes in regional cerebral blood flow were observed within each scan condition. Further analyses revealed distinctive patterns of change related specifically to verbal or figural recognition, as well as longitudinal changes common to all scan conditions. These findings demonstrate that the older brain undergoes functional reorganization with increasing age in healthy, cognitively stable individuals. In view of the stable memory performance, the task-dependent results suggest that age-related changes in brain activity help maintain cognitive function with advancing age.

Aged↗
PubMed2005

Using voxel-based morphometry to map the structural changes associated with rapid conversion in MCI: a longitudinal MRI study.

Capturing the dynamics of gray matter (GM) atrophy in relation to the conversion from mild cognitive impairment (MCI) to clinically probable Alzheimer's disease (AD) would be of considerable interest. In this prospective study we have used a novel longitudinal voxel-based method to map the progression of GM loss in MCI patients over time and compared converters to non-converters. Eighteen amnestic MCI patients were followed-up for a predefined fixed period of 18 months and conversion was judged according to NINCDS-ADRDA criteria for probable AD. Each patient underwent a high-resolution T1-weighted volume MRI scan both at entry in the study and 18 months later. We used an optimal VBM protocol to compare baseline imaging data of converters to those of non-converters. Moreover, to map GM loss from baseline to follow-up assessment, we used a modified voxel-based morphometry (VBM) procedure specially designed for longitudinal studies. At the end of the follow-up period, seven patients had converted to probable AD. Areas of lower baseline GM value in converters mainly included the hippocampus, parahippocampal cortex, and lingual and fusiform gyri. Regions of significant GM loss over the 18-month follow-up period common to both converters and non-converters included the temporal neocortex, parahippocampal cortex, orbitofrontal and inferior parietal areas, and the left thalamus. However, there was significantly greater GM loss in converters relative to non-converters in the hippocampal area, inferior and middle temporal gyrus, posterior cingulate, and precuneus. This accelerated atrophy may result from both neurofibrillary tangles accumulation and parallel pathological processes such as functional alteration in the posterior cingulate. The ability to longitudinally assess GM changes in MCI offers new perspectives to better understand the pathological processes underlying AD and to monitor the effects of treatment on brain structure.

Aged↗
PubMed2005

Longitudinal evidence of the impact of normal thyroid stimulating hormone variations on cognitive functioning in very old age.

The purpose of this study was to examine longitudinal associations among thyroid stimulating hormone (TSH) levels and cognitive performance. Data collected at the first three assessment times, approximately 3 years apart, are reported for the survivors (n=45) from a previously published cross-sectional study. Participants were aged 75-93 years at baseline, and data reported were collected in the Kungsholmen Project, a longitudinal project investigating aging and dementia. Analyses revealed that although declining verbal fluency and visuospatial abilities were accompanied by simultaneously declining TSH levels, the pattern of cross-sectional and longitudinal results are interpreted such that declining TSH levels may have caused episodic memory deficits later on. These results were obtained in the examination of 6-year but not 3-year change, and after removal of the cognitive variation associated with depressive mood symptoms.

Affect↗
PubMed2005

Exhaled carbon monoxide levels in atopic asthma: a longitudinal study.

Exhaled carbon monoxide (eCO) is a potential non-invasive marker of airway inflammation. We have investigated the cross-sectional and longitudinal relationship between eCO and lung function and bronchial reactivity in 69 adults with atopic asthma, in the course of participation in a 6-week randomised placebo-controlled trial of vitamin E supplementation. At baseline, there was no cross-sectional association between absolute eCO levels and either forced expiratory volume (FEV(1)), forced vital capacity (FVC) or bronchial reactivity. However, in the longitudinal analysis within the placebo group, a rise in mean eCO was significantly associated with improvement in bronchial reactivity (change in eCO (parts per million) per natural log unit change in bronchial hyperreactivity 0.498, 95% confidence interval 0.071 to 0.924, P=0.024). These findings suggest that, contrary to previous data, there is no cross-sectional relationship between eCO and lung function or bronchial reactivity, but that there may be a longitudinal trend with bronchial reactivity that is worth further investigation.

Adolescent↗
PubMed2004

Longitudinal studies of cognition and functional outcome in schizophrenia: implications for MATRICS.

It is generally accepted that cognitive deficits in schizophrenia are related to functional outcome. However, support for longitudinal relationships between cognition and functional outcome has not been as well documented. The current paper presents a review of 18 recently published longitudinal studies (minimum 6-month follow up) of the relationships between cognition and community outcome in schizophrenia. Results from these studies reveal considerable support for longitudinal associations between cognition and community outcome in schizophrenia. These studies demonstrate that cognitive assessment predict later functional outcome and provide a rationale for psychopharmacological interventions for cognitive deficits in schizophrenia. Although the relationships between cognition and community outcome are well-supported, it is clear that community functioning is also affected by a host of factors apart from cognition that are usually not considered in clinical trial studies (e.g., psychosocial rehabilitation and educational/vocational opportunities). In the second part of the paper, we consider intervening steps between cognitive performance measures and community outcome. These steps are apt to have important implications for clinical trials of cognition-enhancing agents in schizophrenia.

Antipsychotic Agents↗
PubMed2004

Longitudinal changes in lower urinary tract symptoms among a cohort of black American men: the Flint Men's Health Study.

OBJECTIVES: To examine the progression of lower urinary tract symptoms in a longitudinal population-based cohort of black men. Population-based studies of prostatism and longitudinal data regarding changes in lower urinary tract symptom severity have largely focused on white men, with little attention directed toward black men. METHODS: In 1996, a probability sample of 369 black men, aged 40 to 79 years, residing in Genesee County, Michigan, and without a prior history of prostate cancer/surgery participated in a prostate cancer screening protocol that included completing the American Urological Association Symptom Index (AUASI). Four years after baseline, 175 of the 369 men agreed to participate in the follow-up protocol. Of the 175 men, 149 had not reported undergoing treatment for benign prostatic hyperplasia and had complete symptom data. These men were included in this study. Differences between baseline and follow-up AUASI scores were examined. RESULTS: The mean and standard deviation AUASI scores at baseline and follow-up were 7.1 (6.4) and 7.0 (6.8), respectively. Although overall no statistically significant change was found in the mean AUASI during the 4 years of follow-up (-0.11; SD 6.2; P = 0.7), the average change in the symptom score and the variability in the change increased with patient age at baseline from a mean of -0.42 (SD 5.0) among men in their 40s to 2.1 (SD 6.6) among men in their 70s. Of the 91 men (61.1%) who reported mild to no symptoms (AUASI score 7 or less) at baseline, 24 (26.4%) reported moderate to severe symptoms (AUASI score 8 or more) at follow-up. This progression of symptom severity was observed across all ages. CONCLUSIONS: In this population-based study of longitudinal changes in urinary symptoms in black men, we found a substantial percentage of men demonstrated a measurable progression in urinary symptom severity over time. Additional studies are needed to examine critically any racial differences in lower urinary tract symptom progression.

Adult↗
PubMed2026

Longitudinal whole-genome analysis of bluetongue virus identifies conserved serotype-specific genomes and distinct genomic constellations within a Colorado sheep flock (2021-2023).

Bluetongue virus (BTV) is a segmented double-stranded RNA virus of ruminants transmitted by Culicoides spp. biting midges. Although the genome consists of ten segments, classification into serotypes is primarily based on genome segment 2. However, reassortment among genomic segments is a major driver of BTV evolution and diversity. This study used longitudinal whole-genome sequencing to characterize BTV genomes collected from 2021 to 2023 within a single sheep flock in Colorado, where multiple serotypes co-circulate. Whole-genome sequences were generated from fourteen blood samples representing four serotypes: BTV-6, -11, -13, and -17. Longitudinal sampling identified multiple BTV serotypes within individual sheep across consecutive years. Tanglegram analysis comparing segment phylogenies to the segment 2 tree demonstrated incongruent topologies across all genomic segments, suggestive of reassortment or the circulation of distinct genomic constellations. Nucleotide-level comparisons revealed high sequence homology among same-serotype samples from the same year, while the greatest genetic divergence was observed among BTV-17 genomes collected in different years. Additionally, all BTV-13 genomes contained a previously undescribed nonsynonymous substitution in segment 10 predicted to extend the encoded protein by three amino acids. Together, these findings demonstrate that highly conserved BTV genomes and distinct genomic constellations can be detected at the flock level across multiple years. This longitudinal whole-genome approach reveals the genetic complexity of endemic BTV populations, including novel variants and genomic patterns consistent with reassortment that are lost with conventional serotyped-based approaches, highlighting the need to integrate whole-genome characterization into endemic BTV monitoring programs.

Animals↗
PubMed2006

Overweight status and weight control behaviors in adolescents: longitudinal and secular trends from 1999 to 2004.

BACKGROUND: This study examined 5-year longitudinal and secular trends in weight status and the use of healthy and unhealthy weight control behaviors in adolescents. METHODS: Project EAT-II followed 2516 adolescents from Minnesota longitudinally from 1999 to 2004. The population included two cohorts allowing for the observation of transitions from early to middle adolescence (junior high school to high school) and from middle to late adolescence (high school to post-high school). RESULTS: The prevalence of overweight (females: 28.7%; males: 28.0%) was high in early adolescence and remained high throughout adolescence. In females, between early and middle adolescence, there were steep longitudinal increases in the use of unhealthy weight control behaviors (48.6% to 58.8%, P = 0.001) and extreme weight control behaviors (9.4% to 17.9%, P < 0.001), and between middle and late adolescence, extreme weight control behaviors increased from 14.5% to 23.9% (P < 0.001). In males, extreme weight control behaviors doubled from middle to late adolescence (3.4% to 6.3%, P = 0.023). Use of diet pills doubled from 7.5% to 14.2% from 1999 to 2004 (P = 0.004) in high school females. One fifth (19.9%) of females in late adolescence reported taking diet pills. CONCLUSIONS: Overweight status and unhealthy weight control behaviors in adolescents are major public health concerns that warrant interventions addressing both problems.

Adolescent↗
PubMed1985

Longitudinal changes in three normal facial types.

The purpose of this study was to describe and compare the dentofacial relationships of three normal facial types (long, average, and short). Comparisons of the absolute and incremental changes between 5 years and 25.5 years of age were made both longitudinally and cross-sectionally. The subjects consisted of 20 males and 15 females for whom complete sets of data were available for the period of this study. All subjects had clinically acceptable occlusion and had not undergone previous orthodontic treatment. Descriptive statistics summarized the changes in 48 parameters, including that of height for males and females at 5, 10, 15, and 25.5 years of age. Longitudinal comparisons of the growth curves evaluated the curve profiles and curve magnitudes for the three facial types for both males and females. The analysis of variance was also used to compare the absolute and incremental changes at ages 5, 10, 15, and 25.5 years. The investigation resulted in the following findings. (1) Most persons (77%) have been categorized as having the same facial type at 5 and at 25.5 years of age. There is a strong tendency to maintain the original facial type with age. (2) Comparisons of the growth curves of the different parameters--with the exception of the incremental curves for MP:SN and Pog:NB in males--consistently demonstrated parallelism of the curves, regardless of the facial type. On the other hand, comparisons of curve magnitude indicated significant differences among the three facial types. (3) The persons within each facial type expressed a relatively large variation in the size and relationships of the various dentofacial structures. (4) Significant differences in the dentofacial parameters were present between males and females with the same facial type. The differences among facial types were not identical in males and females. (5) Longitudinal analysis of the data lends more consistent and, therefore, more meaningful results than cross-sectional comparisons when facial growth trends need to be evaluated. This is because growth changes are often subtle and of magnitudes not readily observed when the data are evaluated cross-sectionally. Standards that are age-, sex- and facial type-specific are presented.

Adolescent↗
PubMed2003

Assessing and interpreting treatment effects in longitudinal clinical trials with missing data.

Treatment effects are often evaluated by comparing change over time in outcome measures; however, valid analyses of longitudinal data can be problematic, particularly if some data are missing. For decades, the last observation carried forward (LOCF) approach has been a common method of handling missing data. Considerable advances in statistical methodology and our ability to implement those methods have been made in recent years. Thus, it is appropriate to reconsider analytic approaches for longitudinal data. This review examines the following from a clinical perspective: 1) the characteristics of missing data that influence analytic choices; 2) the attributes of common methods of handling missing data; and 3) the use of the data characteristics and the attributes of the various methods, along with empirical evidence, to develop a robust approach for the analysis and interpretation of data from longitudinal clinical trials. We propose that, in many settings, the primary efficacy analysis should use a repeated measures, likelihood-based, mixed-effects modeling approach, with LOCF used as a secondary, composite measure of efficacy, safety, and tolerability. We illustrate how repeated-measures analyses can be used to enhance decision-making, and we review the caveats that remain regarding the use of LOCF as a composite measure.

Analysis of Variance↗
PubMed1997

Whole blood and plasma water in health and disease: longitudinal and transverse observations and correlations with several different hematological and clinicochemical parameters.

In a healthy reference population, hemoglobin (Hgb) and hematocrit (Hct) have been proposed as surrogate markers for whole blood water (WBW). We have extended this study under different physiological and pathological conditions in two longitudinal series, viz. (1) acute hyper- and hypohydration experiments in a healthy individual and (2) three athletes running 5 km each, and in three transverse series, viz. (3) a young reference population (n = 97, 49 females), (4) an old reference population (n = 37, nine females) consisting of inhabitants of a nursing home and (5) cardiac, hematological and renal patients including severe anaemia, polycythaemia and abnormal protein levels (n = 50, 25 females) with suspected hydration disturbances. The only sex difference found was a lower WBW in males in the young reference group. The percentage change of PW was less than that of WBW. In all five groups together (n = 293) WBW correlated closely (P < 0.0001) with Hgb and Hct (both r = -0.95) and with erythrocyte count (r = -0.85), whereas PW correlated with total protein (Tprot) (r = -0.84). In the longitudinally studied groups (1) and (2) WBW also correlated (P < 0.0001) with cholesterol, Ca, Tprot, albumin, platelets, globulin and white blood cells (r +/- 0.98-0.37), while PW correlated (P < 0.0001) not only with the same clinicochemical parameters but also with Hct, Hgb and red blood cells (r +/- 0.98-0.44). The homeostasis of PW is more narrowly regulated than that of WBW. Hgb, Hct and erythrocyte count reflect WBW and Tprot reflects PW also under disease conditions. WBW (mass%) can be calculated from Hgb and Hct using the formulae: -0.09 x Hgb (g/l) + 91.7 and -28.6 x Hct (v/v) + 91.8 and PW (mass%) from Tprot using the formula: -0.09 x Tprot (g/l) + 97.6. Other correlations were observed only in a longitudinal setting and presumably are due to concentration and dilution.

Adult↗
PubMed2002

Changes in serum lipid levels during a 10 year period in a large Japanese population. A cross-sectional and longitudinal study.

To determine the recent secular trends in serum lipid levels and characterize their influence on the aging process, we examined a large cohort of Japanese cross-sectionally and longitudinally. The participants included 80331 Japanese men and women 20-79 years of age, who had received annual health examinations from 1989 to 1998. In cross-sectional analysis, an increase in total and LDL cholesterol as well as triglyceride levels was observed in the population during the period of 1989-1998. The longitudinal changes showed that total and LDL cholesterol increased with age in men between the birth cohorts of the 1920s and 1960s. In women, these cholesterol levels increased in the 1930s and younger cohorts. HDL cholesterol decreased in men of all birth cohorts. However, HDL cholesterol increased in women of the 1940s and younger cohorts. Triglyceride levels increased in men of the 1940s and younger cohorts but decreased in the 1930s and older. Triglyceride levels increased in women of the 1930s and younger. Longitudinal analysis also suggested a birth cohort effect except for the triglyceride level for women. These results suggest that Japanese serum lipid levels continue to increase and that there exist birth cohort effects regarding serum lipid levels in the Japanese population.

Adult↗
PubMed1998

Peak bone mineral accrual and age at menarche in adolescent girls: a 6-year longitudinal study.

BACKGROUND AND OBJECTIVES: The greatest increase in bone mineral content occurs during adolescence. The amount of bone accrued may significantly affect bone mineral status in later life. We carried out a longitudinal investigation of the magnitude and timing of peak bone mineral content velocity (PBMCV) in relation to peak height velocity (PHV) and the age at menarche in a group of adolescent girls over a 6-year period. METHODS: The 53 girls in this study are a subset of the 115 girls (initially 8 to 16 years) in a 6-year longitudinal study of bone mineral accretion. The ages at PBMCV and PHV were determined by using a cubic spline curve fitting procedure. Determinations were based on height (n = 12) and bone (n = 6) measurements over 6 years. RESULTS: The timing of PBMCV and menarche were coincident, preceded approximately 1 year earlier by PHV. Correlation showed a negative relationship between age at menarche and both peak bone mineral accrual (r = -0.42, P < .002) and PHV (r = -0.45, P < .001). CONCLUSIONS: This longitudinal study demonstrated the close association between age at PBMCV and age at menarche and confirmed the relationship between greater PBMCV and PHV in earlier, as compared with later, maturing girls.

Adolescent↗
PubMed2002

Concomitant longitudinal changes in frequency of and bother from lower urinary tract symptoms in community dwelling men.

PURPOSE: Care for men with benign prostatic hyperplasia consumes a sizable amount of health care resources, which is largely driven by bother from lower urinary tract symptoms. While cross-sectional studies have demonstrated a strong correlation between frequency of symptoms and associated bother, there are few longitudinal data demonstrating how these track together. MATERIALS AND METHODS: In 1989, 2,115 white men between 40 and 79 years old were recruited from a random sample of the Olmsted County population. These men completed a self-administered questionnaire that assessed lower urinary tract symptom severity and associated bother with questions similar to those in the American Urological Association Symptom Index. Questionnaires were completed biennially thereafter through 1996. RESULTS: Annualized changes in symptom score increased from a median of 0.02 per year (25th, 75th percentile -0.35, 0.60) for men in their forties to 0.43 (-0.12, 1.16) for men in their sixties. The median change in bother scores was 0 (-0.30, 0.29) across all ages. The correlation between longitudinal symptom score slopes and bother score slopes was 0.55 (p <0.001) overall and did not differ substantively across age. CONCLUSIONS: These results demonstrate that there is a great deal of variability between individuals in the amount of longitudinal change in lower urinary tract symptom severity and bother. While for bother, there is little change across individuals on average, within individual frequency and bother track together fairly closely. However, there remain some men with increases in frequency who do not report similar increases in bother, possibly representing some component of adaptation or acceptance of worsening symptom severity with age.

Adult↗
PubMed2002

Functional cerebral asymmetries during the menstrual cycle: a cross-sectional and longitudinal analysis.

This study aims at answering two basic questions regarding the mechanisms with which hormones modulate functional cerebral asymmetries. Which steroids or gonadotropins fluctuating during the menstrual cycle affect perceptual asymmetries? Can these effects be demonstrated in a cross-sectional (follicular and midluteal cycle phases analyzed) and a longitudinal design, in which the continuous hormone and asymmetry fluctuations were measured over a time course of 6 weeks? To answer these questions, 12 spontaneously cycling right-handed women participated in an experiment in which their levels of progesterone, estradiol, testosterone, LH, and FSH were assessed every 3 days by blood-sample based radioimmunoassays (RIAs). At the same points in time their asymmetries were analyzed with visual half-field (VHF) techniques using a lexical decision, a figure recognition, and a face discrimination task. Both cross-sectional and longitudinal analyzes showed that an increase of progesterone is related to a reduction in asymmetries in a figure recognition task by increasing the performance of the left-hemisphere which is less specialized for this task. Cross-sectionally, estradiol was shown to have significant relationships to the accuracy and the response speed of both hemispheres. However, since these effects were in the same direction, asymmetry was not affected. This was not the case in the longitudinal design, where estradiol affected the asymmetry in the lexical decision and the figural comparison task. Overall, these data show that hormonal fluctuations within the menstrual cycle have important impacts on functional cerebral asymmetries. The effect of progesterone was highly reliable and could be shown in both analysis schemes. By contrast, estradiol mainly, but not exclusively, affected both hemispheres in the same direction.

Adult↗
PubMed2003

Longitudinal multicenter follow-up of high-risk infants: why, who, when, and what to assess.

This article reviews experience with longitudinal follow-up of high-risk infants in the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network. In 1993, the Network initiated a research protocol to provide longitudinal follow-up of infants with birth weight less than 1001 g and infants with higher birth weights who participated in certain Network randomized trials. Infants are assessed at 18 to 22 months corrected age (corrected for degree of prematurity) using measures of the infant's health, growth, neuromotor, and early cognitive functioning, language, behavior, and family resources. Data from these assessments have been used to investigate potentially modifiable risk factors for cerebral palsy and delayed early cognitive functioning and to evaluate the risks and benefits of interventions assessed in randomized trials. The Network's experience thus far suggests that longitudinal follow-up can provide valuable information about treatments given to fetuses and neonates.

Cerebral Palsy↗
PubMedDate not supplied

Dyspnea in patients with chronic obstructive pulmonary disease: does dyspnea worsen longitudinally in the presence of declining lung function?

OBJECTIVE: To determine the direction and rate of change in the symptom of dyspnea in patients with chronic obstructive pulmonary disease (COPD) whose lung function has worsened over time. DESIGN: Secondary analysis of a longitudinal data set. SETTING: Outpatient clinic. PATIENTS: Thirty-four medically stable male subjects with chronic obstructive pulmonary disease studied for 5.3 +/- 3.5 years, with a mean reduction in FEV1 over the period studied of 330.9 +/- 288.0 mL. Subjects were 63.3 +/- 5.5 years of age at entry into the study. OUTCOME MEASURES: Dyspnea and functional status scores were obtained using the Pulmonary Functional Status and Dyspnea Questionnaire. RESULTS: There was no significant difference in reports of dyspnea from the beginning to the end of the study, despite significant reductions in lung function. Of all activities studied, dyspnea when raising arms overhead was the only activity showing a relationship to the slope of change in FEV1 %. CONCLUSION: These findings suggest that, although patients with chronic lung disease experience varying degrees of deterioration in lung function longitudinally, there is no evidence that they report worsening of dyspnea in tandem with these physiologic changes. In this study, patient ratings of dyspnea longitudinally were not directly linked to changes in lung impairment.

Disease Progression↗
PubMed2002

Guidelines for the design of clinical trials with longitudinal outcomes.

A common objective of longitudinal clinical trials is to compare rates of change in a continuous response variable between two groups. The power realized for such a study is a function of both the number of people recruited and the planned number of measurements for each participant. By varying these two quantities in opposite directions, power can be kept at the desired level. We consider the problem of how best to choose the sample size and frequency of measurement, with a view to minimizing either the total number of measurements or the cost of a study. Some general guidelines are first developed for the situation in which all participants have complete observations. In practice, however, longitudinal studies often suffer from dropout, where a participant leaves the study permanently so that no further observations are possible. We therefore consider the impact of unanticipated dropout on power and also ways of allowing for dropout at the design stage. Based on our results, we propose some general design guidelines for longitudinal trials comparing rates of change when dropout is present.

Clinical Trials as Topic↗