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PubMed2006

Adiponectin is present in human milk and is associated with maternal factors.

BACKGROUND: Previous studies have shown that human milk has a role in the gastrointestinal, neural, and immune development of neonates. If present in milk, adiponectin would be a promising candidate for influencing infant development, given its metabolic functions. OBJECTIVES: Our objectives were to determine whether adiponectin is present in human milk and to characterize maternal factors associated with potential variation in milk adiponectin concentrations. DESIGN: We quantified adiponectin concentrations in human milk samples from donors to the Cincinnati Children's Research Human Milk Bank and randomly selected participants in a cohort study in Mexico City funded by the National Institutes of Health. Using cross-sectional and longitudinal data, we examined milk adiponectin concentrations in relation to lactation duration, maternal body mass index (BMI; in kg/m(2)), and ethnicity. RESULTS: Adiponectin was detected in human skim milk (range: 4.2-87.9 ng/mL). In cross-sectional and longitudinal analyses, duration of lactation was negatively associated with milk adiponectin concentrations (beta = -0.059 +/- 0.024 and -0.059 +/- 0.007, respectively; P < 0.02 for both). Maternal postpregnancy BMI was positively associated with milk adiponectin concentrations (beta = 0.08 +/- 0.02, P < 0.0001; longitudinal analysis). Mexican mothers had lower median milk adiponectin concentrations at 1 mo than did the non-Hispanic white subjects from Cincinnati (11.5 and 19.8 ng/mL; P = 0.003). CONCLUSIONS: Adiponectin is present in human milk and its concentrations are associated with duration of lactation, maternal adiposity, and ethnicity. Given the importance of adiponectin in inflammation, insulin sensitivity, and fatty acid metabolism, future studies should examine milk adiponectin's role in infant metabolic development.

Adiponectin↗

PubMed2000

Long-term relations of personality and health: dynamisms, mechanisms, tropisms.

There is now little doubt that individuals who are well-adjusted, socially stable, and well-integrated into their communities are at significantly lower risk for disease and premature mortality than those who are more unstable, impulsive, isolated, and alienated. The reasons for these associations, however, are complex and the pathways insufficiently studied. This article employs a life-span data set to explore how childhood personality relates to health-related growth and development (dynamisms), patterns of reactions and health behaviors (mechanisms), and movements toward and away from suitable environments (tropisms). Illustrations from the 7-decade Terman longitudinal data reveal important areas in which previous, cross-sectional research has misinterpreted associations between personality and health. In particular, Sociability has been overrated as a life-span health risk factor, Conscientiousness has been underrated, and Neuroticism has been confused. Without sufficient attention to the processes underlying the associations between personality and health, significant suboptimal allocations of intervention resources result.

Adolescent↗

PubMed1991

Statistical issues in the study of temporal data: daily experiences.

This article reviews statistical issues that arise in temporal data, particularly with respect to daily experience data. Issues related to nonindependence of observations, the nature of data structures, and claims of causality are considered. Through the analysis of data from a single subject, we illustrate concomitant time-series analysis, a general method of examining relationships between two or more series having 50 or more observations. We also discuss detection of and remedies for the problems of trend, cycles, and serial dependency that frequently plague temporal data, and present methods of combining the results of concomitant time series across subjects. Issues that arise in pooling cross-sectional and time-series data and statistical models for addressing these issues are considered for the case in which there are appreciably fewer than 50 observations and a moderate number of subjects. We discuss the possibility of using structural equation modeling to analyze data structures in which there are a large number (e.g., 200) of subjects, but relatively few time points, emphasizing the different causal status of synchronous and lagged effects and the types of models that can be specified for longitudinal data structures. Our conclusion highlights some of the issues raised by temporal data for statistical models, notably the important roles of substantive theory, the question being addressed, the properties of the data, and the assumptions underlying each technique in determining the optimal approach to statistical analysis.

Adaptation, Psychological↗

PubMedDate not supplied

The two faces of adolescents' success with peers: adolescent popularity, social adaptation, and deviant behavior.

This study assessed the hypothesis that popularity in adolescence takes on a twofold role, marking high levels of concurrent adaptation but predicting increases over time in both positive and negative behaviors sanctioned by peer norms. Multimethod, longitudinal data, on a diverse community sample of 185 adolescents (13 to 14 years), addressed these hypotheses. As hypothesized, popular adolescents displayed higher concurrent levels of ego development, secure attachment, and more adaptive interactions with mothers and best friends. Longitudinal analyses supported a popularity-socialization hypothesis, however, in which popular adolescents were more likely to increase behaviors that receive approval in the peer group (e.g., minor levels of drug use and delinquency) and decrease behaviors unlikely to be well received by peers (e.g., hostile behavior with peers).

Achievement↗

PubMed2003

Genome-wide linkage analysis using cross-sectional and longitudinal traits for body mass index in a subsample of the Framingham Heart Study.

To evaluate linkage evidence for body mass index (BMI) using both cross-sectional and longitudinal data, we performed genome-wide multipoint linkage analyses on subjects who had complete data at four selected time points (initial, 8th, 12th, and 16th year following the initial visit) from the Framingham Heart Study. The cross-sectional measures included BMI at each of the four selected time points and the longitudinal measure was the within-subject mean of BMI at the above four time points. Using the variance components method, we consistently observed the maximum LOD score out of the genome scan using BMI at each time point and the mean of BMI between 049xd2 and GATA71H05 on chromosome 16. The highest LOD score (3.0) was at time point 1, while the lowest (1.9) was at time point 4. We also observed other suggestive linkages on chromosome 6, 10, and 18 at time point 1 only. The longitudinal measure we studied (mean of BMI) did not provide greater power to identify a positive linkage than some of the cross-sectional measures (e.g., time point 1). The changing of linkage evidence over time provided some insights on the variation of genetic effect on BMI with aging. There may be a QTL on chromosome 16 that contributes to BMI and this locus, and maybe others, is more likely to affect BMI during early adulthood.

Adult↗

PubMed1978

Differences and changes in VO2 among young runners 10 to 18 years of age.

Twenty young males, all active in middle-distance running, were studied between January 1968 and May 1974 for the purpose of gathering longitudinal data regarding Vo2 during treadmil running. Vo2 submax (measured during the last 2 min of a 6-min run at 202 m/min) and Vo2 max values (measured during a 5-8 min increasing-speed run to exhaustion) were collected approximately every 6 months for 6 years. Different groups, starting at ages of 10, 12 and 13 years were followed for periods of 2 to 5 years continuously. In all longitudinal comparisons. Vo2 max (ml/min) changes peralleled changes in body weight; consequently, Vo2 max (ml/kg.min-1) did not show a significant change. In every group Vo2 submax (ml/kg.min-1) dropped significantly over time. All data were pooled by 1 yr age groups, providing cross-sectional data for active boys 10-18 yrs of age. Vo2 max ranged from 1933 ml/min for 10-yr olds to 4082 for 18-year olds. Concurrent changes in weight resulted in no significant differences in Vo2 max (ml/kg.min-1) from the overall mean of 61.5 Vo2 submax (ml/kg.min-1) was highest among 10-year olds (53.3) and lowest among 18-yr olds (42.5). Based on these longitudinal and cross sectional findings and significant improvements in times for 1- and 2-mile races, it was concluded that Vo2 max (ml/min) increases no faster than does body weight among moderately active growing boys and that both age and training contribute to a change in Vo2 submax; a factor which accounts greatly for improvements in middle-distance race performance.

Adolescent↗

PubMed2003

Low neuropsychologic performance among adult cancer survivors treated with chemotherapy.

Decline in neuropsychologic test performance following adjuvant chemotherapy for various types of cancer has gained much research attention over the past decade. From available data, about one fourth to one third of individuals undergoing systemic chemotherapy exhibit measurable decrements in performance of standard tests of cognitive function. Many cancer survivors report that cognitive problems interfere with function and compromise quality of life. However, these declines appear subtle and there are little available longitudinal data examining pre- to post-treatment cognitive change. Further, there is little available evidence identifying the causes of cognitive decline. This paper reviews current literature on low neuropsychologic performance following systemic chemotherapy and hypotheses on the causes of cognitive symptoms following chemotherapy. Future research directions, with emphasis on longitudinal research design as well as treatment implications, are discussed.

Adult↗

PubMed1998

Development of an enterovirus specific PCR method for the quantification of enterovirus genomes in blood of diabetes patients.

BACKGROUND: Insulin-dependent diabetes mellitus or type 1 diabetes is a disease with a diverse aetiology. Epidemiological studies examining newly diagnosed, recent onset IDDM patients have suggested a role for viruses in the aetiology of IDDM (Yoon, 1995, Diabetes/Metabolism Reviews 11, 83-107). Important candidates are the enteroviruses, in particular coxsackieviruses B3 and B4. The latter can cause diabetes in animals (Clements et al., 1995, Lancet 346, 221-223). OBJECTIVES: We have developed a quantitative PCR method for the detection of enterovirus genomes in biological samples. The quantitative PCR will be used to screen for enteroviruses in blood of diabetes patients and their relatives by testing a Blood Diabetes Register. STUDY DESIGN: A substantial amount of data has been collected on enterovirus induced IDDM, our study is original in so far as it will be: (1) a quantitative study, not only the presence of viral genome sequences in blood will be determined, but also their concentrations (viral load); and (2) a longitudinal study, samples are and will be collected as a function of time. Positive PCR samples will be quantified using the standard addition method. RESULTS: The test is specific for enteroviruses, since all enteroviruses were detected with equal sensitivity. Viruses belonging to other picornavirus genera scored negative (even up to 3 x 10(6) genome copies). An equal detection limit of 10 genome copies was found for all enteroviruses. CONCLUSIONS: The developed method will permit us to generate quantitative and longitudinal data of enterovirus genomes in blood of diabetes patients and their relatives, which might help in the elucidation of the relationship between enteroviruses and IDDM.

Diabetes Mellitus, Type 1↗

PubMed1997

Characteristics of long-surviving men: results from a nine-year longitudinal study.

Although the life expectancy of men is commonly less than that of women, previous analyses of a longitudinal data set revealed a sub-sample of older men whose survival curves over twenty years are similar to those of the women in the sample. The main purpose of this research is to identify factors which differentiate this group of "successful" males from the other males in the sample. Data from the two groups of males (and two groups of females) were examined using analysis of variance, chi 2 analysis, and survival analysis. Data include measures in a variety of biomedical, functional, behavioral, and psychological areas collected during in-home and hospital examinations. Results show that "successful" males have significantly higher scores in both cognitive abilities and health, initially and at longitudinal follow-ups. The combination of overall high scores in the multiple domains evidently gives this group of men an advantage over the others. The results emphasize the importance of recognizing the sub-groups in the aging population with different developmental patterns, and tailoring both research and services to the uniqueness of these groups.

Aged↗

PubMed1996

Explaining urban-rural variations in health: a review of interactions between individual and environment.

In order to gain insight into the relation between health and people's environment, literature published between 1985 and 1994 was gathered from several international databases. An introduction into existing theory regarding geographic disparities is presented: geographical drift and breeder hypotheses are discussed. This is followed by a critical review focusing on interaction effects of urbanicity and individual characteristics on health. This leads to two major conclusions. First, emphasis in past research has been primarily on urban constraints rather than opportunities. Positive aspects of urban living are often insufficiently appreciated. Second, positive and negative environmental aspects have an effect on health that is often dependent on individual characteristics. The extent to which the environment exerts influence on a person's health is dependent on that person's individual characteristics. These conclusions are relevant only for further developing the breeder hypothesis, however. Large scale individual based longitudinal data should be studied in order to gain more insight into the relative importance of the geographical drift hypothesis.

Health Status Indicators↗

PubMed2005

Using multilevel models to analyze couple and family treatment data: basic and advanced issues.

Couple and family treatment data present particular challenges to statistical analyses. Partners and family members tend to be more similar to one another than to other individuals, which raises interesting possibilities in the data analysis but also causes significant problems with classical, statistical methods. The present article presents multilevel models (also called hierarchical linear models, mixed-effects models, or random coefficient models) as a flexible analytic approach to couple and family longitudinal data. The article reviews basic properties of multilevel models but focuses primarily on 3 important extensions: missing data, power and sample size, and alternative representations of couple data. Information is presented as a tutorial, with a Web appendix providing datasets with SPSS and R code to reproduce the examples.

Couples Therapy↗

PubMed2000

Reparameterizing the pattern mixture model for sensitivity analyses under informative dropout.

Pattern mixture models are frequently used to analyze longitudinal data where missingness is induced by dropout. For measured responses, it is typical to model the complete data as a mixture of multivariate normal distributions, where mixing is done over the dropout distribution. Fully parameterized pattern mixture models are not identified by incomplete data; Little (1993, Journal of the American Statistical Association 88, 125-134) has characterized several identifying restrictions that can be used for model fitting. We propose a reparameterization of the pattern mixture model that allows investigation of sensitivity to assumptions about nonidentified parameters in both the mean and variance, allows consideration of a wide range of nonignorable missing-data mechanisms, and has intuitive appeal for eliciting plausible missing-data mechanisms. The parameterization makes clear an advantage of pattern mixture models over parametric selection models, namely that the missing-data mechanism can be varied without affecting the marginal distribution of the observed data. To illustrate the utility of the new parameterization, we analyze data from a recent clinical trial of growth hormone for maintaining muscle strength in the elderly. Dropout occurs at a high rate and is potentially informative. We undertake a detailed sensitivity analysis to understand the impact of missing-data assumptions on the inference about the effects of growth hormone on muscle strength.

Aged↗

PubMed1998

Evidence that upregulation of serum IGF-1 concentration can trigger acceleration of diabetic retinopathy.

BACKGROUND: Acute reduction of chronic hyperglycaemia can accelerate early diabetic retinopathy. In adolescent patients with Mauriac's syndrome, this phenomenon is related to an upregulation of subnormal serum IGF-1 levels. AIM: To obtain longitudinal data on serum IGF-1 and retinopathy status in poorly controlled adult insulin dependent (type 1) diabetic patients without Mauriac's syndrome, in whom hyperglycaemia is reduced by intensive insulin therapy. METHODS: Four patients with chronic severe insulin deficiency and early micro-angiopathy were studied prospectively. Changes in plasma glucose, HbA1c, serum IGF-1 levels, proteinuria, retinopathy, and clinical status were followed up closely. RESULTS: Reducing hyperglycaemia from > 16 mmol/l (equivalent to HbA1c > 11%) to < 10 mmol/l (HbA1c < 8%) within 5 months increased serum IGF-1 levels by 70-220%. While proteinuria and symptomatic neuropathy regressed, retinopathy progressed from the mild to the severe non-proliferative stage with maculopathy (n = 4), and to the proliferative stage (n = 1). Laser coagulation was commenced upon the appearance of sight threatening macular oedema (n = 4). CONCLUSION: Upregulation of serum IGF-1 preceding retinal deterioration in these patients suggests a cause-effect relation, consistent with earlier experimental and clinical data.

Adult↗

PubMed2005

Reflections on DSM classification and its utility in primary care: case studies in "mental disorders".

BACKGROUND: This case series was conducted to demonstrate the limitations of the DSM system in primary care patients. METHOD: Sixty family health center patients free of mental disorders according to DSM-IV criteria completed monthly quantitative interviews, using multiple rating instruments, concerning the levels of psychiatric symptoms, presence of distress and/or a mental disorder, functional status, support, and stressors. In addition, a purposive sample of 16 subjects completed an in-depth qualitative interview concerning their situation at the time they crossed a DSM threshold. Data were collected from April 2000 to March 2001. RESULTS: Overall, there were 14 subjects with distress alone, 6 subjects with subthreshold disorders, and 3 subjects with known transient (< 2 months' duration) threshold disorders. Thus, even with the incomplete longitudinal data in this study, the clinical needs of 23 (38%) of the original 60 subjects were inadequately met by the DSM criteria. From the 10 subjects who crossed a DSM threshold and completed a qualitative interview, we selected 5 case studies with the most complete and complementary quantitative and qualitative data to illustrate several findings regarding the utility of the DSM classification in primary care. First, these cases show that psychological symptoms and DSM disorders vary considerably. Second, distress and subthreshold disorders are often seen in primary care patients. Third, the crossing of a DSM threshold corresponds to extreme levels of psychological symptoms and may therefore represent symptom severity. Fourth, psychological symptoms are often linked to physical illness. Finally, the context in which these symptoms and disorders develop often produces complex dynamic patterns. CONCLUSIONS: The current DSM system failed to adequately reflect the spectrum and context of mental illness in patients from a predominantly low-income, Hispanic primary care population.

Journal Article↗

PubMed2005

Trajectories of Marijuana Use During the Transition to Adulthood: The Big Picture Based on National Panel Data.

The purposes of this study were to: a) identify trajectory groups of frequent marijuana use during emerging adulthood, b) distinguish among trajectory groups according to demographic and lifestyle characteristics, and c) examine how the trajectory groups relate to behavioral, attitudinal, and social-emotional correlates over time. National panel data from the Monitoring the Future study were used: 18 cohorts of high school seniors (classes of 1977-94) were followed biennially through age 24. Frequent marijuana use was defined as 3+ occasions of use in past month and/or 20 to 40+ occasions in past year. Based on four waves of complete longitudinal data (N=19,952), six frequent marijuana use trajectory groups were identified: chronic, decreased, increased, fling, rare, and abstain. Categorical analyses revealed trajectory group differences in demographic and lifestyle characteristics at senior year and age 24. The trajectory groups varied significantly in longitudinal patterns of other substance use, problem behaviors, and well-being.

Journal Article↗

PubMed2005

Assessment of patient functional status after surgery.

BACKGROUND: Improvement in day-to-day functioning is a valued outcome of surgical intervention. A new functional status assessment instrument, the Activities Assessment Scale (AAS), was designed for a randomized clinical trial evaluating laparoscopic versus open hernia repair procedures. STUDY DESIGN: The study data set included 2,164 patients at baseline and 1,562 patients at 3-month followup. Only male patients were enrolled in the trial. The psychometric characteristics of the AAS were examined in statistical analyses of cross-sectional and longitudinal data from the trial. Correlational analyses, factor analyses, and t-tests were used to evaluate scale performance. RESULTS: We found that the AAS was a reliable measure (Cronbach's Coefficient Alpha =0.85) in the patient population studied. Factor analyses identified three subscales (sedentary activities; ambulatory activities; work and exercise activities). Construct validity was demonstrated by a correlation of 0.65 between the AAS and the physical functioning (PF) dimension of the SF-36 (p < 0.001); comparisons between clinical subgroups further confirmed its validity (p < 0.001). Patients reporting improvement on the physical functioning dimension after surgery showed an effect size of 1.20 for preoperative-postoperative change in their AAS scores. CONCLUSIONS: The AAS has been demonstrated to be a reliable, valid, and clinically responsive instrument that can be used to evaluate patient functioning after hernia surgery. It is easy to administer and requires less than 5 minutes of patient time to complete. This measurement system may prove useful in assessing surgical outcomes in both research and office practice settings.

Activities of Daily Living↗

PubMed2006

A major depression prognosis calculator based on episode duration.

BACKGROUND: Epidemiological data have shown that the probability of recovery from an episode declines with increasing episode duration, such that the duration of an episode may be an important factor in determining whether treatment is required. The objective of this study is to incorporate episode duration data into a calculator predicting the probability of recovery during a specified interval of time. METHODS: Data from two Canadian epidemiological studies were used, both studies were components of a program undertaken by the Canadian national statistical agency. One component was a cross-sectional psychiatric epidemiological survey (n = 36,984) and the other was a longitudinal study (n = 17,262). RESULTS: A Weibull distribution provided a good description of episode durations reported by subjects with major depression in the cross-sectional survey. This distribution was used to develop a discrete event simulation model for episode duration calibrated using the longitudinal data. The resulting estimates were then incorporated into a predictive calculator. During the early weeks of an episode, recovery probabilities are high. The model predicts that approximately 20% will recover in the first week after diagnostic criteria for major depression are met. However, after six months of illness, recovery during a subsequent week is less than 1%. CONCLUSION: The duration of an episode is relevant to the probability of recovery. This epidemiological feature of depressive disorders can inform prognostic judgments. Watchful waiting may be an appropriate strategy for mild episodes of recent onset, but the risks and benefits of this strategy must be assessed in relation to time since onset of the episode.

Journal Article↗

PubMed2001

Transforming self-rated health and the SF-36 scales to include death and improve interpretability.

BACKGROUND: Most measures of health-related quality of life are undefined for people who die. Longitudinal analyses are often limited to a healthier cohort (survivors) that cannot be identified prospectively, and that may have had little change in health. OBJECTIVE: To develop and evaluate methods to transform a single self-rated health item (excellent to poor; EVGGFP) and the physical component score of the SF-36 (PCS) to new variables that include a defensible value for death. METHODS: Using longitudinal data from two large studies of older adults, health variables were transformed to the probability of being healthy in the future, conditional on the current observed value; death then has the value of 0. For EVGGFP, the new transformations were compared with some that were published earlier, based on different data. For the PCS, how well three different transformations, based on different definitions of being healthy, discriminated among groups of patients, and detected change in time were assessed. RESULTS: The new transformation for EVGGFP was similar to that published previously. Coding the 5 categories as 95, 90, 80, 30, and 15, and coding dead as 0 is recommended. The three transformations of the PCS detected group differences and change at least as well as the standard PCS. CONCLUSION: These easily interpretable transformed variables permit keeping persons who die in the analyses. Using the transformed variables for longitudinal analyses of health when deaths occur, either for secondary or primary analysis, is recommended. This approach can be applied to other measures of health.

Aged↗