Evidence of reliability and validity of IPAQ for Mexican-American adults

Physical activity is a key component of life-style modification process which helps to reduce the risk of developing chronic diseases. It is important to have accurate estimates of physical activity to identify sedentary populations where interventions might be helpful. The International Physical Activity Questionnaire (IPAQ) short version has been used to estimate physical activity in diverse populations. However, there is little literature depicting the use of the IPAQ short version in Mexican America population. This study addressed the predictive validity and test-retest reliability of the IPAQ short version in Mexican American adults. The analysis was performed on 97 participants enrolled in the Cameron County Hispanic Cohort. Individuals selected in this study were 18 years of age or older. The predictive validity was evaluated by studying the relationship between physical activity and biomarkers known to be correlated with physical activity, namely, TNF-α, Adiponectin, and HDL. Multiple linear regression analysis was performed to delineate predictive validity. To assess test-retest reliability, two IPAQ-short last seven days questionnaires were interviewer administered to the participants on the same day, approximately two hours apart. Test-Retest reliability of IPAQ was estimated by performing intraclass correlations between the readings at two different time periods. The study showed that the IPAQ – short version used in the above study had acceptable test-retest reliability in the Mexican American population. This study showed that the IPAQ – short version did not have acceptable predictive validity when looking at physical activity and TNF-α, Adiponectin, and HDL in this sample.^

Affect and cognition measures in preference-based decisions: Validity testing of the Ottawa Decisional Conflict Scale and a decision-specific anxiety measure with men eligible for prostate cancer screening

Background. At present, prostate cancer screening (PCS) guidelines require a discussion of risks, benefits, alternatives, and personal values, making decision aids an important tool to help convey information and to help clarify values. Objective: The overall goal of this study is to provide evidence of the reliability and validity of a PCS anxiety measure and the Decisional Conflict Scale (DCS). Methods. Using data from a randomized, controlled PCS decision aid trial that measured PCS anxiety at baseline and DCS at baseline (T0) and at two-weeks (T2), four psychometric properties were assessed: (1) internal consistency reliability, indicated by factor analysis intraclass correlations and Cronbach's α; (2) construct validity, indicated by patterns of Pearson correlations among subscales; (3) discriminant validity, indicated by the measure's ability to discriminate between undecided men and those with a definite screening intention; and (4) factor validity and invariance using confirmatory factor analyses (CFA). Results. The PCS anxiety measure had adequate internal consistency reliability and good construct and discriminant validity. CFAs indicated that the 3-factor model did not have adequate fit. CFAs for a general PCS anxiety measure and a PSA anxiety measure indicated adequate fit. The general PCS anxiety measure was invariant across clinics. The DCS had adequate internal consistency reliability except for the support subscale and had adequate discriminate validity. Good construct validity was found at the private clinic, but was only found for the feeling informed subscale at the public clinic. The traditional DCS did not have adequate fit at T0 or at T2. The alternative DCS had adequate fit at T0 but was not identified at T2. Factor loadings indicated that two subscales, feeling informed and feeling clear about values, were not distinct factors. Conclusions. Our general PCS anxiety measure can be used in PCS decision aid studies. The alternative DCS may be appropriate for men eligible for PCS. Implications: More emphasis needs to be placed on the development of PCS anxiety items relating to testing procedures. We recommend that the two DCS versions be validated in other samples of men eligible for PCS and in other health care decisions that involve uncertainty. ^

Effect of nonnormal random components on level and power in group-randomized trials

The use of group-randomized trials is particularly widespread in the evaluation of health care, educational, and screening strategies. Group-randomized trials represent a subset of a larger class of designs often labeled nested, hierarchical, or multilevel and are characterized by the randomization of intact social units or groups, rather than individuals. The application of random effects models to group-randomized trials requires the specification of fixed and random components of the model. The underlying assumption is usually that these random components are normally distributed. This research is intended to determine if the Type I error rate and power are affected when the assumption of normality for the random component representing the group effect is violated. ^ In this study, simulated data are used to examine the Type I error rate, power, bias and mean squared error of the estimates of the fixed effect and the observed intraclass correlation coefficient (ICC) when the random component representing the group effect possess distributions with non-normal characteristics, such as heavy tails or severe skewness. The simulated data are generated with various characteristics (e.g. number of schools per condition, number of students per school, and several within school ICCs) observed in most small, school-based, group-randomized trials. The analysis is carried out using SAS PROC MIXED, Version 6.12, with random effects specified in a random statement and restricted maximum likelihood (REML) estimation specified. The results from the non-normally distributed data are compared to the results obtained from the analysis of data with similar design characteristics but normally distributed random effects. ^ The results suggest that the violation of the normality assumption for the group component by a skewed or heavy-tailed distribution does not appear to influence the estimation of the fixed effect, Type I error, and power. Negative biases were detected when estimating the sample ICC and dramatically increased in magnitude as the true ICC increased. These biases were not as pronounced when the true ICC was within the range observed in most group-randomized trials (i.e. 0.00 to 0.05). The normally distributed group effect also resulted in bias ICC estimates when the true ICC was greater than 0.05. However, this may be a result of higher correlation within the data. ^

Multiple imputation for missing continuous and dichotomous data: The effects of patterns of missingness and variable correlations on type I error with small samples

The purpose of this study is to investigate the effects of predictor variable correlations and patterns of missingness with dichotomous and/or continuous data in small samples when missing data is multiply imputed. Missing data of predictor variables is multiply imputed under three different multivariate models: the multivariate normal model for continuous data, the multinomial model for dichotomous data and the general location model for mixed dichotomous and continuous data. Subsequent to the multiple imputation process, Type I error rates of the regression coefficients obtained with logistic regression analysis are estimated under various conditions of correlation structure, sample size, type of data and patterns of missing data. The distributional properties of average mean, variance and correlations among the predictor variables are assessed after the multiple imputation process. ^ For continuous predictor data under the multivariate normal model, Type I error rates are generally within the nominal values with samples of size n = 100. Smaller samples of size n = 50 resulted in more conservative estimates (i.e., lower than the nominal value). Correlation and variance estimates of the original data are retained after multiple imputation with less than 50% missing continuous predictor data. For dichotomous predictor data under the multinomial model, Type I error rates are generally conservative, which in part is due to the sparseness of the data. The correlation structure for the predictor variables is not well retained on multiply-imputed data from small samples with more than 50% missing data with this model. For mixed continuous and dichotomous predictor data, the results are similar to those found under the multivariate normal model for continuous data and under the multinomial model for dichotomous data. With all data types, a fully-observed variable included with variables subject to missingness in the multiple imputation process and subsequent statistical analysis provided liberal (larger than nominal values) Type I error rates under a specific pattern of missing data. It is suggested that future studies focus on the effects of multiple imputation in multivariate settings with more realistic data characteristics and a variety of multivariate analyses, assessing both Type I error and power. ^

The association of sexual behavior with oropharyngeal cancer and correlations with HPV-16 serologic status

Objectives. This hospital-based case-case study compared the characteristics of sexual behavior in patients with cancer of the oropharynx to patients with cancers of other head and neck sites. Additionally, the prevalence of certain sexual behaviors of HPV-16 seropositive head and neck cancer patients was compared to that of seronegative patients. ^ Methods. One hundred sixty five oropharyngeal cancer patients and 86 patients with cancers of other head and neck sites completed a sexual history questionnaire. ^ Results. Oropharyngeal cancer patients were significantly more likely to have had a greater number of lifetime sex partners, to have engaged in oral-genital sex, and to have had a greater number of oral-genital sex partners than non-oropharyngeal cancer patients. Oral-genital sex was significantly more common in the HPV-16 seropositive group. ^ Conclusion. These findings add to the evidence that HPV-16 is sexually transmitted to the upper aerodigestive tract and that certain sexual behaviors increase the risk for HPV-associated oropharyngeal cancer. ^

A Bayesian approach to estimating the intraclass correlation coefficient

A Bayesian approach to estimating the intraclass correlation coefficient was used for this research project. The background of the intraclass correlation coefficient, a summary of its standard estimators, and a review of basic Bayesian terminology and methodology were presented. The conditional posterior density of the intraclass correlation coefficient was then derived and estimation procedures related to this derivation were shown in detail. Three examples of applications of the conditional posterior density to specific data sets were also included. Two sets of simulation experiments were performed to compare the mean and mode of the conditional posterior density of the intraclass correlation coefficient to more traditional estimators. Non-Bayesian methods of estimation used were: the methods of analysis of variance and maximum likelihood for balanced data; and the methods of MIVQUE (Minimum Variance Quadratic Unbiased Estimation) and maximum likelihood for unbalanced data. The overall conclusion of this research project was that Bayesian estimates of the intraclass correlation coefficient can be appropriate, useful and practical alternatives to traditional methods of estimation. ^

Behavioral responses to methylphenidate: correlations with neuronal activity in the caudate nucleus

Methylphenidate is currently a drug of abuse and readily prescribed to both adolescents and adults. Chronic methylphenidate (MPH) exposure results in an increase in DA in the motive circuit, including the caudate nucleus (CN), similar to other drugs of abuse. This study focuses on research aimed to elucidate if there are intrinsic underlying differences in the CN electrophysiological activity of animals exhibiting different chronic responses to the same dose of MPH. Behavioral and caudate nucleus (CN) neuronal activity following acute and chronic doses of MPH was assessed by simultaneously recording the behavioral and neuronal activity. The experimental protocol lasted for 10 days using four groups; saline, 0.6, 2.5 and 10.0mg/kg MPH. Initially, the study determined that animals exposed to the same dose of MPH exhibited either behavioral sensitization or behavioral tolerance. Therefore animals were classified into two groups (behaviorally sensitized/tolerant) and their neuronal activity was evaluated. Four hundred and fifty one units were evaluated. Overall, a mixture of increases and decreases in CN neuronal populations was observed at initial MPH exposure, and at ED10 baseline and ED10 rechallenge. When separated based on their behavioral response (sensitized/tolerant), significant differences in neuronal response patterns was revealed. Animals exhibiting sensitization were more likely to increase their neuronal activity at ED1 and ED10 baseline, expressing the opposite response at ED10 rechallenge. Furthermore, when neuronal populations recorded from those animals exhibiting behavioral sensitization were statistically compared to those from animals exhibiting behavioral tolerance significant differences were observed. Collectively, these findings tell us that animals exposed to the same dose of MPH can respond oppositely and moreover that there is in fact some intrinsic difference in the two population’s neuronal activity. This study offers new insight into the electrophysiological differences between sensitized and tolerant animals.