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PubMed2006

Change in pulse wave velocity throughout normal pregnancy and its value in predicting pregnancy-induced hypertension: a longitudinal study.

OBJECTIVE: We longitudinally examined the changes of brachial to ankle distensibility using pulse wave velocity (PWV) throughout pregnancy and its difference between normal pregnancy and pregnancy-induced hypertension (PIH) groups. STUDY DESIGN: One hundred and eighty-three pregnant women were included in this study. The PWV examinations were performed in a longitudinal way during the first, second, and third trimesters of pregnancy, and immediately and 1 month after delivery. RESULTS: In normal pregnancies, the PWV significantly decreased at the second trimester, increased from the third trimester through immediately after delivery, and decreased again at 1 month after delivery. In PIH patients, it increased in proportion to the progression of gestation. CONCLUSION: We monitored the longitudinal changes in PWV and constructed a PWV normogram during pregnancy. The predictive value of PWV and blood pressure for PIH was higher than that of blood pressure alone, suggesting the usefulness of measuring PWV to predict PIH.

Adolescent↗

PubMed2004

Longitudinal physical activity and sedentary behavior trends: adolescence to adulthood.

BACKGROUND: There is little national research on longitudinal patterns of physical activity and sedentary behavior in ethnically diverse teens as they transition to adulthood. METHODS: Longitudinal questionnaire data from U.S. adolescents enrolled in Wave I (1994-1995) and Wave III (2001) of the National Longitudinal Study of Adolescent Health (n =13,030) were analyzed in January 2004. Incidence, reversal, and maintenance of achieving five or more weekly bouts of moderate to vigorous physical activity (MVPA) and < or =14 hours of weekly TV and video viewing, computer/video game use (screen time) were assessed. Multinomial logistic regression models examined the likelihood of achieving five or more weekly sessions of MVPA week and < or =14 hours screen time per week as an adolescent and/or young adult, controlling for household income, parental education, age of adolescent, and seasonality. RESULTS: Of those achieving five or more weekly sessions of MVPA and < or =14 hours of weekly screen time as adolescents, few continued to achieve these favorable amounts of activity (4.4%) and screen time (37.0%) as adults. More failed to maintain these favorable amounts of activity (31.1%) and screen time (17.3%) into adulthood. Black versus white females were more likely to maintain less [corrected] favorable amounts of activity from adolescence to adulthood (odds ratio [OR]=3.09; 95% confidence interval [CI]=1.49-6.42), while black males (OR=1.50; CI=1.05-2.14) and females (OR=2.00; CI=1.40-2.87) were more likely than whites to maintain less (versus more) favorable screen time hours. CONCLUSIONS: The vast majority of adolescents do not achieve five or more bouts of moderate physical activity per week, and continue to fail to achieve this amount of activity into adulthood.

Adolescent↗

PubMed2006

Participation in occupational health longitudinal studies: predictors of missed visits and dropouts.

PURPOSE: The purpose of this study is to determine whether demographics, health, and job factors influence continued participation of employed persons in a longitudinal intervention study of tertiary prevention for work-related low-back disorders (WR-LBDs). METHODS: Four hundred fifty-four actively employed persons had enrolled in an intervention study of back supports and education to promote recovery from a WR-LBD. Baseline values were examined according to whether individuals continued in the study, missed a visit, or dropped out; frequency of missed visits; and early or late dropouts at follow-up intervals of 1, 2, 6, and 12 months. RESULTS: Workers who did not complete all study visits were significantly more likely to be younger and have poorer self-reported health. Individuals with a greater percentage of body fat dropped out early. Significantly more missed visits were observed among those who had arthritis and longer duration of low-back pain symptoms. Job factors did not influence study participation. CONCLUSIONS: Continued participation in a longitudinal study of working adults was influenced by age, health status, and factors related to the primary condition targeted by the intervention study. Strategies aimed at those who report lower levels of health and symptoms related to the condition under study may promote follow-up participation in longitudinal studies. Thus, even among actively employed persons, one should not assume that all workers are "healthy."

Adiposity↗

PubMed2006

Adiposity in adolescents: change in actual BMI works better than change in BMI z score for longitudinal studies.

PURPOSE: Longitudinal epidemiologic studies often relate adiposity changes to suspected causal factors. In growing adolescents, this becomes complicated. Many investigators use within-child change in body mass index (BMI) z scores (Delta z) from sex- and age-specific BMI charts developed by the Centers for Disease Control and Prevention (CDC). These charts, derived from cross-sectional data, may not represent BMI growth patterns of real children. Furthermore, because cross-sectional BMIs are not Gaussian, these z scores are from month-specific transformed distributions, with possible unintended consequences when used longitudinally. Alternatively, we can directly analyze BMI change (Delta BMI). We compare these two widely used measures of change in adiposity. METHODS AND RESULTS: With real adolescent data, we show that annual Delta BMIs have nonlinear peaks that are inconsistent with the CDC curves. We also show that a specified Delta z represents a broad range of adiposity changes for children measured at the same two ages. To see how this affects power, we performed simulation studies confirming that analyzing Delta BMIs in models with hypothesized factors is more powerful than analyzing Delta zs. CONCLUSIONS: In longitudinal studies of adolescent adiposity, investigators should be encouraged to analyze Delta BMI rather than Delta z because analyses using BMI are more powerful and findings presented in BMI units are more interpretable.

Adipose Tissue↗

PubMed2026

Retention strategies and participant retention rates among prospective longitudinal pregnancy cohorts: a systematic mapping review.

Prospective longitudinal pregnancy cohorts can answer questions about fetal and early life exposures and later health outcomes; however, there are challenges to retaining participants in longitudinal studies, particularly over life transitions like the birth of a child. Optimal methods for retaining participants in longitudinal research are unclear. A systematic mapping review was conducted to identify prospective cohort studies and randomized controlled trials that enrolled pregnant participants and their infants. Data on retention rates and 17 retention strategies was extracted. A random effects meta-analysis generated pooled annual retention rates inversely weighted to the number of baseline participants. Spearman rank coefficients were used to assess correlation between strategy use and retention. A random-effects meta-regression was used to determine if select retention strategies were associated with participant retention. We identified 130 studies, involving 472 022 pregnancies. A downward trend in pooled mean retention rates were observed. Studies utilized an average of 6.8 (SD 3.9) retention strategies. Statistically significant associations were not observed between strategy use and retention rates at follow-up (p > 0.05). Prospective studies of pregnant people and their infants used multiple retention strategies. Participant retention rates declined over time, suggesting that additional factors may influence study participation in the postpartum period.

Humans↗

PubMed2004

Detecting and tracking local changes in the tibiae of individual rats: a novel method to analyse longitudinal in vivo micro-CT data.

In this study we present the analysis of in vivo micro-CT scans using a new method based on image registration that accurately evaluates longitudinal micro-CT studies. We tested if detailed changes in the bone architecture could be detected and tracked in individual animals. A prototype in vivo micro-CT scanner (Skyscan 1076) was developed in which tibiae of rats that are lying on a bed under gas anaesthesia were scanned. For this study, three female Wistar rats were used: a sham-operated rat, an ovariectomised (OVX) rat and one rat that served as a reproducibility control. The reproducibility control rat was scanned twice in 1 day. The other animals were scanned at week 0, just before surgery, at week 4 and at week 14 after surgery. Architectural changes over time were detected by overlaying two data sets made at different time points using an algorithm that uses mutual information for optimal registration. The scans were segmented into binary data sets using a local thresholding algorithm. The reproducibility test showed small errors of less than 3% in bone volume measurements and errors less than 0.5% in measurements of trabecular thickness. The sham-operated rat showed no changes in total bone volume, though thinning and eventual loss of some small trabeculae could be detected, which could be related to the age of the animal. The OVX rat lost much trabecular bone volume, especially in the metaphysis (60% at week 4, 75% at week 14). The remaining trabeculae slowly increased in thickness. Following the different scans in time showed the forming of new trabecular structures. Additionally, small longitudinal growth at the growth plate could be detected after the first 4 weeks. Further, the OVX rat showed extensive modelling at the proximal endosteal lateral cortex. We have shown a new method that can detect and track changes in the local bone architecture and individual trabeculae in time, in an individual living animal. This method enables longitudinal in vivo micro-CT studies and has the potential to greatly contribute to experimental rat or mouse studies on pharmacological intervention and transgenic models.

Animals↗

PubMed2006

Use of OSWALD for analyzing longitudinal data with informative dropout.

OSWALD (Object-oriented Software for the Analysis of Longitudinal Data) is flexible and powerful software written for S-PLUS for the analysis of longitudinal data with dropout for which there is little other software available in the public domain. The implementation of OSWALD is described through analysis of a psychiatric clinical trial that compares antidepressant effects in an elderly depressed sample and a simulation study. In the simulation study, three different dropout mechanisms: completely random dropout (CRD), random dropout (RD) and informative dropout (ID), are considered and the results from using OSWALD are compared across mechanisms. The parameter estimates for ID-simulated data show less bias with OSWALD under the ID missing data assumption than under the CRD or RD assumptions. Under an ID mechanism, OSWALD does not provide standard error estimates. We supplement OSWALD with a bootstrap procedure to derive the standard errors. This report illustrates the usage of OSWALD for analyzing longitudinal data with dropouts and how to draw appropriate conclusions based on the analytic results under different assumptions regarding the dropout mechanism.

Humans↗

PubMed2005

Assessing missing data assumptions in longitudinal studies: an example using a smoking cessation trial.

Due to the chaotic nature of the clinical disorder, longitudinal data analysis in substance abuse research is plagued by missing values. To obtain an unbiased estimation on intervention effects, different longitudinal modeling strategies require various assumptions on the patterns and mechanisms of missing data. By defining missingness as intermittent missingness (occasional omission) and dropout (premature withdrawal), this article demonstrates statistical ways for assessing missing data assumptions using evidence from a clinical trial. Within the framework of multiple imputation, intermittent missing data are imputed first so that dropouts can be isolated and treated specifically. A computational tool called "pattern reduction resampling" is proposed to simplify missing data methods when the number of intra-subject repeated measures is large. To test whether missingness patterns are nondifferential across treatment conditions, a formal testing approach treats indicators of missingness as a special type of repeated measures (e.g., 0: intermittent missing, 1: observed, and 2: dropout missing). After reviewing the idea of ignorability for missing data and of classifying missingness mechanisms into subcategories, the article provides an example for assessing common assumptions on missingness mechanisms and how these assumptions affect model selection for significance testing. A carbon monoxide longitudinal data set in a smoking cessation study is used for illustration.

Bias↗

PubMed2026

Longitudinal progression, metrics, age-dependence, and modifiers of ataxia severity in SCA27B: a multicentre study of 219 patients.

BACKGROUND: Spinocerebellar Ataxia 27B (SCA27B) is a novel, frequent and likely treatable late-onset autosomal-dominant ataxia caused by GAA repeat-expansions in FGF14. For understanding disease evolution and imminent trial planning, metrics of the most widely used clinical outcome assessment (Scale for the Assessment and Rating of Ataxia/SARA), longitudinal progression and modifiers thereof are warranted. METHODS: Multicentre intercontinental observational study (2015-2024) of 661 assessments from 219 patients with SCA27B (age: 68 ± 10 years; SARA: 9 ± 6 points) with item-level distribution-based analyses to characterise SARA metrics relative to ageing-related impairment in 390 healthy controls; and linear mixed-effects modelling to determine longitudinal progression and demographic or genetic modifiers. FINDINGS: Ataxia severity in SCA27B as assessed by SARA was primarily attributable to gait, stance, and lower-limb impairment; other ataxia domains scored ≤1 SARA point in 79-94% of patients. Discrimination of SCA27B motor performance from controls decreased with age due to ageing-related motor variability captured by SARA, thus limiting potential metric response windows for symptomatic treatments. Disease progression was faster in the presence of interfering ageing-related comorbidities in 14 (6%) patients. Overall longitudinal progression of SCA27B was 0.54 SARA points/year [95% CI: 0.37-0.71]. Expansions of (GAA)> 180 repeats were frequent also on the shorter allele (n = 18 (8%), range: 196-348 repeats), and associated with faster progression (+1.6 SARA points/year, [95% CI: 0.9-2.2]), including also otherwise less affected ataxia domains speech and sitting. INTERPRETATION: Disease progression in SCA27B is characterised by mild progression, ageing-related motor variabilities and comorbidities, and associated with repeat size on both alleles. FUNDING: Else-Kröner-Fresenius-Stiftung, EU, DFG, BMBF, CIHR, NAF, Ataxia-UK, CSC.

Humans↗

PubMed2024

Phthalates and sex steroid hormones across the perimenopausal period: A longitudinal analysis of the Midlife Women's Health Study.

BACKGROUND: The menopausal transition involves significant sex hormone changes. Environmental chemicals, such as urinary phthalate metabolites, are associated with sex hormone levels in cross-sectional studies. Few studies have assessed longitudinal associations between urinary phthalate metabolite concentrations and sex hormone levels during menopausal transition. METHODS: Pre- and perimenopausal women from the Midlife Women's Health Study (MWHS) (n = 751) contributed data at up to 4 annual study visits. We quantified 9 individual urinary phthalate metabolites and 5 summary measures (e.g., phthalates in plastics (∑Plastic)), using pooled annual urine samples. We measured serum estradiol, testosterone, and progesterone collected at each study visit, unrelated to menstrual cycling. Linear mixed-effects models and hierarchical Bayesian kernel machine regression analyses evaluated adjusted associations between individual and phthalate mixtures with sex steroid hormones longitudinally. RESULTS: We observed associations between increased concentrations of certain phthalate metabolites and lower testosterone and higher sub-ovulatory progesterone levels, e.g., doubling of monoethyl phthalate (MEP), monobenzyl phthalate (MBzP), di-2-ethylhexyl phthalate (∑DEHP) metabolites, ∑Plastic, and ∑Phthalates concentrations were associated with lower testosterone (e.g., for ∑DEHP: -4.51%; 95% CI: -6.72%, -2.26%). For each doubling of MEP, certain DEHP metabolites, and summary measures, we observed higher mean sub-ovulatory progesterone (e.g., ∑AA (metabolites with anti-androgenic activity): 6.88%; 95% CI: 1.94%, 12.1%). Higher levels of the overall time-varying phthalate mixture were associated with lower estradiol and higher progesterone levels, especially for 2nd year exposures. CONCLUSIONS: Phthalates were longitudinally associated with sex hormone levels during the menopausal transition. Future research should assess such associations and potential health impacts during this understudied period.

Humans↗

PubMed2005

Serum antimullerian hormone levels best reflect the reproductive decline with age in normal women with proven fertility: a longitudinal study.

OBJECTIVE: The aim of this study was to assess which of the basal ovarian reserve markers provides the best reflection of the changes occurring in ovarian function over time (i.e., reproductive aging). DESIGN: Prospective longitudinal study. SETTING: Healthy volunteers in an academic research center. PATIENT(S): Eighty-one women with normal reproductive performance during the course of their lives were longitudinally assessed. In this select group of women, becoming chronologically older was considered as a proxy variable for becoming older from a reproductive point of view. INTERVENTION(S): The women were assessed twice, with on average a 4-year interval (T(1) and T(2)). The number of antral follicles on ultrasound (AFC) and blood levels of antimullerian hormone (AMH), FSH, inhibin B, and E(2) were assessed. MAIN OUTCOME MEASURE(S): Longitudinal changes of the markers mentioned and the consistency of these parameters over time. RESULT(S): The mean ages at T(1) and T(2) were 39.6 and 43.6 years, respectively. Although AFC was strongly associated with age in a cross-sectional fashion, it did not change over time. The AMH, FSH, and inhibin B levels showed a significant change over time, in contrast to E(2) levels. The AMH and AFC were highly correlated with age both at T(1) and T(2), whereas FSH and inhibin B predominantly changed in women more than 40 years of age. To assess the consistency of these parameters over time, we investigated whether a woman's individual level above or below the mean of her age group at T(1) remained above or below the mean of her age group at T(2). Serum AMH concentrations showed the best consistency, with AFC as second best. The FSH and inhibin B showed only modest consistency, whereas E(2) showed no consistency at all. CONCLUSION(S): These results indicate that serum AMH represents the best endocrine marker to assess the age-related decline of reproductive capacity.

Adult↗

PubMed2004

Statistical measures were proposed for identifying longitudinal patterns of change in quantitative health indicators.

OBJECTIVE: To propose statistical measures to identify different longitudinal patterns of change in quantitative health indicators. METHODS: The authors propose several simple measures to discriminate between stable-unstable, increasing-decreasing, linear-nonlinear, monotonic-nonmonotonic patterns of change. They then suggest using factor analysis to select the subset of nonredundant measures, and cluster analysis, based on the selected measures, to identify subgroups of patients with similar longitudinal trajectories. The proposed approach is illustrated using data on osteoarthritis disability from a longitudinal study undertaken in Toronto, Ontario, in 1996-2001. Disability was measured at four points in time for 835 patients, using the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index. RESULTS: The proposed measures allowed the detection of individual patients with specific patterns of change and identification of four different groups of patients with WOMAC scores that are (1) regularly increasing, (2) regularly decreasing, (3) stable over time, or (4) highly unstable, with abrupt changes or short-term fluctuations. CONCLUSION: The proposed approach may be used to (1) screen even large databases to identify particular patterns of change; or (2) summarize different patterns of change by classifying patients into groups with similar trajectories. Once identified, the groups can be investigated to determine whether there are differences in patient characteristics or outcomes.

Aged↗

PubMed2005

A systematic literature review of attrition between waves in longitudinal studies in the elderly shows a consistent pattern of dropout between differing studies.

OBJECTIVES: Longitudinal studies of the elderly are complicated by the loss of individuals between waves due to death or other dropout mechanisms. Factors that affect dropout may well be similar from one study to another. This article systematically reviews all large population-based studies of the elderly (published 1966-2002) that report on differences in individual characteristics between people who remain and people who dropout at follow-up. STUDY DESIGN AND SETTING: A systematic review of articles that investigate attrition after baseline interview. RESULTS: Twelve studies were found that investigated dropout other than death using unadjusted, multivariable methods or both. The unadjusted analyses showed many significant factors related to attrition. Multivariable analyses showed two main independent factors were related to increased attrition: increasing age and cognitive impairment. People who were very ill or frail had higher dropout rates, and people in worse health were less likely to be recontactable. CONCLUSIONS: Multivariable methods of analyzing attrition in longitudinal studies show consistent patterns of dropout between differing studies, with a small number of key relationships. These findings will assist researchers when planning studies of older people, and provide insight into the possible biases in longitudinal studies introduced by differential dropout.

Age Factors↗

PubMed2006

The cognitive bases of learning to read and spell in Greek: evidence from a longitudinal study.

We conducted a longitudinal study examining the role of phonemic awareness, phonological processing, and grammatical skills in the development of reading and spelling abilities in Greek. A battery of cognitive, linguistic, and literacy tasks was administered to 131 primary school children (65 7-year-olds and 66 9-year-olds) and was repeated in the following year (8- and 10-year-olds, respectively). Phoneme awareness, speech rate, and rapid automatized naming (RAN) were concurrent predictors of reading rate at Time 1 (T1), and speech rate was a longitudinal predictor of reading rate at Time 2 (T2) when reading at T1 was controlled. The predictors of spelling differed from those of reading; phoneme awareness and speech rate predicted concurrent attainments at T1, and phoneme awareness was a robust longitudinal predictor. Despite the differences in the degree of transparency between the Greek and English orthographies, phoneme awareness predicts variations in learning to read and spell in both languages.

Child↗

PubMed2004

Bone mineral density and osteoarthritis: data from the Baltimore Longitudinal Study of Aging.

BACKGROUND: Numerous cross-sectional studies have shown that persons with radiographic features of osteoarthritis (OA) of the hips and knees have higher adjusted levels of bone mineral density (BMD). OBJECTIVE: Data from the Baltimore Longitudinal Study of Aging were examined to determine (1) whether persons with radiographic features of OA of the hands and knees had different rates of bone loss than subjects with normal knee radiographs, and (2) whether persons with normal knee radiographs who had higher adjusted levels of BMD were at greater risk of developing radiographic features of knee OA. DESIGN: Longitudinal cohort study. SUBJECTS: 298 Caucasian men and 139 Caucasian women aged 20 and above who had radiographs of the hands and knees read for features of OA and two or more measurements of BMD at the forearm at least 4 years apart. 179 Caucasian men and 110 Caucasian women aged 20 and above who had longitudinal knee radiographs on average 10 years apart, a subgroup of whom had baseline measurement of lumbar spine and/or femoral neck BMD. RESULTS: Women with radiographic OA of the hand had a significantly greater adjusted rate of bone loss at the radius than women with normal hand radiographs; no such differences were noted in men for hand OA. There were no significant differences in adjusted rate of bone loss at the radius in men or women by presence of radiographic knee OA. Higher BMD at the lumbar spine but not at the femoral neck was associated with an increased risk of developing incident radiographic knee OA after adjustment for age, gender, and body mass index. CONCLUSIONS: These data demonstrate that persons with radiographic OA lose bone at different rates than those with normal radiographs and that this relationship varies between the site of OA and the site of measurement of BMD. In addition, they further support a role for higher bone mass in the development of radiographic knee OA. Further studies are needed to examine the relationship between changes in bone mass and radiographic progression of OA.

Adult↗

PubMed2006

Statistical analysis of longitudinal psychiatric data with dropouts.

Longitudinal studies are used in psychiatric research to address outcome changes over time within and between individuals. However, because participants may drop out of a study prematurely, ignoring the nature of dropout often leads to biased inference, and in turn, wrongful conclusions. The purpose of the present paper is: (1) to review several dropout processes, corresponding inferential issues and recent methodological advances; (2) to evaluate the impact of assumptions regarding the dropout processes on inference by simulation studies and an illustrative example using psychiatric data; and (3) to provide a general strategy for practitioners to perform analyses of longitudinal data with dropouts, using software available commercially or in the public domain. The statistical methods used in this paper are maximum likelihood, multiple imputation and semi-parametric regression methods for inference, as well as Little's test and index of sensitivity to nonignorability (ISNI) for assessing statistical dropout mechanisms. We show that accounting for the nature of the dropout process influences results and that sensitivity analysis is useful in assessing the robustness of parameter estimates and related uncertainties. We conclude that recording the causes of dropouts should be an integral part of any statistical analysis with longitudinal psychiatric data, and we recommend performing a sensitivity analysis when the exact nature of the dropout process cannot be discerned.

Antidepressive Agents↗

PubMed2004

The beta(2)-adrenergic receptor Arg16-gly polymorphism and interactions involving beta(2)- and beta(3)-adrenergic receptor polymorphisms are associated with variations in longitudinal serum lipid profiles: the Bogalusa Heart Study.

We examined the effects of combined genotypes of the beta(2)-adrenergic receptor (AR) Arg(16)-Gly and beta(3)-AR Trp(64)-Arg polymorphisms on longitudinal serum total (T-C) and low-density lipoprotein cholesterol (LDL-C) profiles in 1,198 subjects examined multiple times (6,488 observations) from 1973 to 1996 in the Bogalusa Heart Study, at ages from 4.5 to 38 years. Within 5-year age groups, T-C was significantly (P <.05) higher in beta(2)-AR Arg(16)/Arg(16) homozygotes than in Gly(16) carriers among those 4 to 8 (171.4 +/- 30.0 v 161.5 +/- 27.7 mg/dL), 9 to 13 (167.7 +/- 28.6 v 162.4 +/- 27.4 mg/dL), and 14 to 18 (158.8 +/- 29.6 v 154.7 +/- 27.5 mg/dL) years of age, but not in those 19 to 23, 24 to 28, 29 to 33, or 34 to 38 years of age. The beta(3)-AR polymorphism was not associated with variation in either T-C or LDL-C. In multilevel polynomial growth curve models, the combination of the beta(2)-AR Arg(16)/Arg(16) genotype with either the beta(3)-AR Arg(64)/Arg(64) or Trp(64)/Arg(64) genotypes, denoted AA/AX, was associated with variation in longitudinal T-C (P <.01) and LDL-C (P <.01) profiles. The association between combined beta(2)/beta(3)-AR genotype and lipid profiles differed among race/sex groups, being most marked in black females, in whom the AA/AX combination was associated with higher T-C and LDL-C profiles across all ages. In White males, the AA/AX combination was most strongly associated with higher lipids in adults. In black males and white females, lipid profiles differed little between genotype groups. Our findings suggest that the beta(2)-AR Arg(16)-Gly genotype influences T-C and LDL-C levels in an age-specific manner, that it may interact with beta(3)-AR Trp(64)-Arg genotypes to influence longitudinal T-C and LDL-C profiles, and that the effect of combined beta(2)/beta(3)-AR genotypes on T-C and LDL-C profiles may differ among race/sex groups.

Age Factors↗

PubMed2006

Longitudinal genetic analysis of executive function in elderly men.

The objective of this study was to characterize the relative contribution of genetic and environmental influences to individual differences in longitudinal performance and decline of executive function (EF) using a population-based prospective study of male, WWII veteran twins (NHLBI twin study). Three tests of EF were administered when the twins were 59-70 years old, with 9- and 13-year follow-up. APOE epsilon4 allele status was incorporated in the genetic models to determine its contribution to longitudinal genetic variability. Mean EF performance significantly worsened over time. EF performance was highly genetically correlated across repeat assessment. There were significant genetic influences on 9- and 13-year decline in digit symbol performance. For all tasks decline over the last 4-year follow-up was influenced by individual-specific environmental effects. Controlling for APOE epsilon4 allele presence did not appreciably change the magnitude of genetic effects. These results suggest that common genetic factors underlie longitudinal EF task performance. Genetic influences on EF decline, however, appear to be evident at longer time intervals between assessments.

Aged↗