Longitudinal Measurement Invariance of the Metabolic Syndrome: Is the Assessment of the Metabolic Syndrome Stable Over Time?

Dietary iodine, seaweed consumption, and incidence risk of metabolic syndrome among postmenopausal women: a prospective analysis of the Korean Multi-Rural Communities Cohort Study (MRCohort)

PURPOSE

Despite a beneficial role of iodine and seaweed consumption against metabolic syndrome (MetS), which is high in postmenopausal women, few studies investigated such associations in a prospective study. This study aimed to investigate the association of dietary iodine and seaweed consumption with the incidence of MetS and its components in postmenopausal women.

METHODS

A total of 2588 postmenopausal women aged ≥ 40 years were recruited between 2005 and 2011 in the Multi-Rural Communities Cohort (MRCohort). A validated semiquantitative food frequency questionnaire was used to collect dietary intake data. MetS was defined as three of five components [abdominal obesity, elevated blood pressure, glucose, triglyceride, and low-high density lipoprotein cholesterol (HDL-C)] and the incidence of MetS was checked every 2-4 years. The incidence rate ratio (IRR) was estimated using a modified Poisson regression model with a robust error estimator.

RESULTS

During the mean follow-up period (3.4 ± 2.1 years), MetS occurred in 481 participants. The median cumulative average iodine intake was 108.9 µg/day (interquartile range, 60.8-190.2 µg/day). In multivariable analyses, average iodine and seaweed consumption were inversely associated with MetS (IRR = 0.61, 95% CI 0.47-0.78 in the highest quartile of iodine intake, P for trend = 0.0018; IRR = 0.52, 95% CI 0.39-0.69 in the highest quartile of seaweed consumption, P for trend = 0.0004). Among MetS components, blood glucose (> 100 mg/dL), blood pressure (≥ 130/85 mmHg), and lipid profiles (triglyceride, ≥ 150 mg/dL and HDL-C, < 50 mg/dL) were significantly inversely associated with dietary iodine and seaweed consumption, but there was no clear association for waist circumference (≥ 85 cm).

CONCLUSION

Dietary iodine and seaweed consumption may be inversely associated with MetS incidence and its individual abnormalities in postmenopausal women.

Measuring Athletic Mental Energy (AME): Instrument Development and Validation

Although considerable research indicates that mental energy is an important factor in many domains, including athletic performance (Cook and Davis, 2006), athletic mental energy (AME) has never been conceptualized and measured. Therefore, the aim of this study was to conceptualize and develop a reliable and valid instrument to assess AME. In Study 1, a focus group interview established the initial framework of AME. Study 2 used a survey to collect athletes' experiences of AME and develop a scale draft titled “Athletic Mental Energy Scale (AMES).” In Study 3, we examined the psychometric properties and the underlying structure of AMES via item analysis, internal consistency, and exploratory factor analysis (EFA). In Study 4, we used confirmatory factor analysis (CFA) to examine AMES's factorial validity; and examined concurrent and discriminant validity by examining correlations with athletes' life stress, positive state of mind, and burnout. In study 5, we examined the measurement invariance of the 6-factor, 18-item AMES with Taiwanese and Malaysian samples. Study 6 examined the predictive validity by comparing AMES scores of successful and unsuccessful martial artists. Across these phases, results showed a 6-factor, 18-item AMES had adequate content validity, factorial structure, nomological validity, discriminant validity, predictive validity, measurement invariance, and reliability. We suggest future studies may use AMES to examine its relationships with athletes' cognition, affect, and performance. The application of AMES in sport psychology was also discussed.

Habitual consumption of soy protein and isoflavones and risk of metabolic syndrome in adults ≥ 40 years old: a prospective analysis of the Korean Multi-Rural Communities Cohort Study (MRCohort)

PURPOSE

Although considerable attention has been paid to the potential benefits of soy protein and isoflavones for preventing metabolic syndrome (MetS) and its components, findings linking habitual consumption of these factors to MetS are limited. This study aimed to evaluate the association of MetS incidence with habitual intake of soy protein/isoflavones among Korean men and women aged ≥ 40 years old who did not have MetS at baseline (n = 5509; 2204 men and 3305 women).

METHODS

Dietary intake of soy protein/isoflavones at baseline and average consumption during follow-up were used.

RESULTS

A significant inverse association between dietary intake and incidence of MetS was found in women (incidence rate ratios, IRR = 0.60, 95% CI = 0.46-0.78, P for trend = 0.0094 for the highest quintile of average soy protein intake compared with the lowest quintile; IRR = 0.57, 95% CI = 0.44-0.74, P for trend = 0.0048 for the highest quintile of average isoflavones intake compared with the lowest quintile). A tendency towards an inverse association was also found in men, although it was not significant for the highest quintile (IRR = 0.80, 95% CI = 0.58-1.11, P for trend = 0.9759, comparing the lowest to the highest quintile of average soy protein intake; IRR = 0.73, 95% CI = 0.53-1.01, P for trend = 0.8956, comparing the lowest to the highest quintile of average isoflavones intake). In terms of individual abnormalities, a significant inverse association was found between soy protein and isoflavones and the incidence of low-high-density lipoprotein cholesterol in both men and women. Abdominal obesity and elevated blood pressure were inversely related to soy protein/isoflavones only in women, and an inverse association of elevated triglyceride appeared only in men.

CONCLUSION

Our findings suggest that habitual intake of soy protein and isoflavones is inversely associated with the risk of MetS and its components. There is likely to be a reverse J-shaped association of average intake with MetS.

Estimators for longitudinal latent exposure models: examining measurement model assumptions

Latent variable (LV) models are increasingly being used in environmental epidemiology as a way to summarize multiple environmental exposures and thus minimize statistical concerns that arise in multiple regression. LV models may be especially useful when multivariate exposures are collected repeatedly over time. LV models can accommodate a variety of assumptions but, at the same time, present the user with many choices for model specification particularly in the case of exposure data collected repeatedly over time. For instance, the user could assume conditional independence of observed exposure biomarkers given the latent exposure and, in the case of longitudinal latent exposure variables, time invariance of the measurement model. Choosing which assumptions to relax is not always straightforward. We were motivated by a study of prenatal lead exposure and mental development, where assumptions of the measurement model for the time-changing longitudinal exposure have appreciable impact on (maximum-likelihood) inferences about the health effects of lead exposure. Although we were not particularly interested in characterizing the change of the LV itself, imposing a longitudinal LV structure on the repeated multivariate exposure measures could result in high efficiency gains for the exposure-disease association. We examine the biases of maximum likelihood estimators when assumptions about the measurement model for the longitudinal latent exposure variable are violated. We adapt existing instrumental variable estimators to the case of longitudinal exposures and propose them as an alternative to estimate the health effects of a time-changing latent predictor. We show that instrumental variable estimators remain unbiased for a wide range of data generating models and have advantages in terms of mean squared error. Copyright © 2017 John Wiley & Sons, Ltd.

Psychometric properties of the Perceived Stress Scale (PSS): measurement invariance between athletes and non-athletes and construct validity

Background

Although Perceived Stress Scale (PSS, Cohen, Kamarack & Mermelstein, 1983) has been validated and widely used in many domains, there is still no validation in sports by comparing athletes and non-athletes and examining related psychometric indices.

Purpose

The purpose of this study was to examine the measurement invariance of PSS between athletes and non-athletes, and examine construct validity and reliability in the sports contexts.

Methods

Study 1 sampled 359 college student-athletes (males = 233; females = 126) and 242 non-athletes (males = 124; females = 118) and examined factorial structure, measurement invariance and internal consistency. Study 2 sampled 196 student-athletes (males = 139, females = 57, M_age = 19.88 yrs, SD = 1.35) and examined discriminant validity and convergent validity of PSS. Study 3 sampled 37 student-athletes to assess test-retest reliability of PSS.

Results

Results found that 2-factor PSS-10 fitted the model the best and had appropriate reliability. Also, there was a measurement invariance between athletes and non-athletes; and PSS positively correlated with athletic burnout and life stress but negatively correlated with coping efficacy provided evidence of discriminant validity and convergent validity. Further, the test-retest reliability for PSS subscales was significant (r = .66 and r = .50).

Discussion

It is suggested that 2-factor PSS-10 can be a useful tool in assessing perceived stress either in sports or non-sports settings. We suggest future study may use 2-factor PSS-10 in examining the effects of stress on the athletic injury, burnout, and psychiatry disorders.

Cross-Sectional and Longitudinal Associations between Egg Consumption and Metabolic Syndrome in Adults ≥ 40 Years Old: The Yangpyeong Cohort of the Korean Genome and Epidemiology Study (KoGES_Yangpyeong)

Since the 1970s, the public has been advised to limit egg consumption even though there is little evidence of any harmful effect of eggs on blood cholesterol. The purpose of this cross-sectional and prospective study was to evaluate the potential association between egg consumption and metabolic syndrome (MetS) and MetS components in adults ≥ 40 years in KoGES_Yangpyeong. Yangpyeong is a rural area in South Korea. A total of 2,887 subjects (men 1,115, women 1,772) were recruited from 2005 to 2009, based on a physical examination and questionnaires administered using standardized protocol. After excluding subjects who had MetS at baseline, 1,663 subjects (675 men, 958 women) were followed for 3.20 years (range: 0.34–8.70). During the follow-up period, MetS occurred in 289 subjects. More than 3 eggs per week was significantly associated with decreased risk of MetS in both men (RR = 0.46, 95% CI, 0.26–0.82, P for trend = 0.1093) and women (RR = 0.54, 95% CI, 0.31–0.93, P for trend 0.0325) compared to non-users. There was a cross-sectional inverse relationship between egg consumption and abdominal obesity in men and women. Also, prospectively, higher egg consumption in men was associated with a decreased risk of high fasting blood glucose (RR = 0.39, 95% CI, 0.22–0.67, P for trend = 0.0042) and high triglycerides (RR = 0.42, 95% CI, 0.22–0.80, P for trend = 0.1080). In conclusion, our findings suggest that higher egg consumption may reduce the risk of MetS both in men and women, and the risk of high fasting blood glucose and high triglycerides in men. Current guidelines regarding egg consumption may need to be re-visited for healthy middle-aged and elderly people.

Validation of Yoon's Critical Thinking Disposition Instrument

PURPOSE

The lack of reliable and valid evaluation tools targeting Korean nursing students' critical thinking (CT) abilities has been reported as one of the barriers to instructing and evaluating students in undergraduate programs. Yoon's Critical Thinking Disposition (YCTD) instrument was developed for Korean nursing students, but few studies have assessed its validity. This study aimed to validate the YCTD. Specifically, the YCTD was assessed to identify its cross-sectional and longitudinal measurement invariance.

METHODS

This was a validation study in which a cross-sectional and longitudinal (prenursing and postnursing practicum) survey was used to validate the YCTD using 345 nursing students at three universities in Seoul, Korea. The participants' CT abilities were assessed using the YCTD before and after completing an established pediatric nursing practicum. The validity of the YCTD was estimated and then group invariance test using multigroup confirmatory factor analysis was performed to confirm the measurement compatibility of multigroups.

RESULTS

A test of the seven-factor model showed that the YCTD demonstrated good construct validity. Multigroup confirmatory factor analysis findings for the measurement invariance suggested that this model structure demonstrated strong invariance between groups (i.e., configural, factor loading, and intercept combined) but weak invariance within a group (i.e., configural and factor loading combined).

CONCLUSIONS

In general, traditional methods for assessing instrument validity have been less than thorough. In this study, multigroup confirmatory factor analysis using cross-sectional and longitudinal measurement data allowed validation of the YCTD. This study concluded that the YCTD can be used for evaluating Korean nursing students' CT abilities.

Risk profiles for metabolic syndrome and its transition patterns for the elderly in Beijing, 1992-2009

There have been few reports on the development of metabolic disorders, especially when they are considered as a cluster. The purpose of this study was to describe risk profiles for metabolic syndrome (MetS) in elderly dwellers in Beijing, and to find their transition patterns over time. Data were derived from Beijing longitudinal study of aging, a community-based cohort study hosted by Xuanwu hospital. There were 3,257 elderly people aged 55 years or over recruited in 1992. MetS was assessed for the years 1992, 2000, and 2009. Finally, 363 subjects with complete information for components of MetS in the three years were included in the study. The criteria of MetS recommended by the joint interim statement criteria were adopted. Latent transition analysis was used to calculate the transition probabilities between adjacent visits. A risk typology consisting of four time-invariant groups was detected based on the components of MetS for all subjects. Low MetS risk group, BP risk group, BP-HDL risk group, and BP-FPG-TG risk group were found. The probability of staying at the same status was higher at the two intervals across 18 years. Four latent groups were extracted based on three assessments for the components of MetS, together with their transition patterns. Findings suggested various trajectories for MetS components. Different combinations of intervention strategy might be needed for MetS risk groups.

Effects of long-term developmental patterns of adiposity on levels of C-reactive protein and fibrinogen among North-American men and women: the Spokane Heart Study

This study examined the heterogeneity in BMI development by identifying distinct developmental trajectories. These trajectories were further investigated by relating them to markers of low-grade inflammation later in life. Data from approximately 400 healthy volunteers participating in the Spokane Heart Study were collected in 2-year intervals, and four waves of data were available for the current analyses. Body weight was measured by BMI and low-grade inflammation by high-sensitivity C-reactive protein (CRP) and fibrinogen. Up to date statistical techniques, i.e., latent class growth models, were used to analyse heterogeneity in body weight, and linear regressions were run to analyse possible associations between trajectories of body weight and CRP/fibrinogen levels. Six trajectories were identified (three stable, two increasing, and one decreasing) which differed significantly on CRP/fibrinogen levels, highlighting the importance of weight trajectories. The differences were only partly explained by variations in lifestyle habits.

Cross-sectional and longitudinal relationships between perceived stress and C-reactive protein in men and women

To date, an examination of the longitudinal relationship between perceived stress and C-reactive protein (CRP) is limited. We explored the relationship between perceived stress and CRP concurrently and across 2 and 4 years in 383 men and women. Multiple linear regressions examined the cross-sectional and longitudinal relationships between baseline stress and counter-stress scores with CRP at baseline, 2 years after baseline and 4 years after baseline, while controlling for covariates (age, smoking status, anti-inflammatory use, oral contraceptive use, physical activity, menopausal status, years since onset of menopause, post-menopausal hormone use and body mass index). Results indicate that stress and counter-stress were not related to CRP in either men or women at study baseline or 2 years later. Across a 4-year time frame, higher stress values were related to higher CRP values in women, but not men. Counter-stress was not related to CRP values in men or women across the 4 years. This study highlights the importance of examining the cross-sectional and longitudinal relationship between perceived stress and inflammation separately in men and women.

Psychometric properties of the adjective rating scale for withdrawal across treatment groups, gender, and over time

The adjective rating scale for withdrawal (ARSW) is commonly used to assess opiate withdrawal in clinical practice and research. The aims of this study were to examine the factor structure of the ARSW, test measurement invariance across gender and treatment groups, and assess longitudinal measurement invariance across the clinical trial. Secondary data analysis of the National Drug Abuse Treatment Clinical Trials Network 000-3, a randomized clinical trial comparing two tapering strategies, was performed. The ARSW was analyzed at baseline, end of taper and 1-month follow-up (N=515 opioid-dependent individuals). A 1-factor model of the ARSW fit the data and demonstrated acceptable reliability. Measurement invariance was supported across gender and taper groups. Longitudinal measurement invariance was not found across the course of the trial, with baseline assessment contributing to the lack of invariance. If change over time is of interest, change from post-treatment through follow-up may offer the most valid comparison.

Measurement invariance of the perceived stress scale and latent mean differences across gender and time

Measurement invariance of the 2-factor model of the Perceived Stress Scale--10-item version (Cohen & Williamson, 1988) was tested across men and women at two time points and in the combined total sample over a 2-year time frame (n = 871). Measurement invariance results indicated that the scale measured the latent factors, stress and counter-stress, equivalently in men and women and over time. With measurement invariance demonstrated, differences in latent means were tested. Results indicated that men had lower levels of frequencies of stressors, and at one time point, higher levels of counter-stress, when compared with women. When examining change in frequencies of stressors and counter-stress over 2 years with the combined male and female sample, stressors remained stable, yet counter-stress increased over time. These findings may aid in the interpretation of results when examining stressors and counter-stress in clinical samples where one would expect stress to increase, whereas positive psychological states decrease.

The metabolic syndrome and coronary artery disease: a structural equation modeling approach suggestive of a common underlying pathophysiology

OBJECTIVE

The purpose of this research was to utilize a structural equation modeling (SEM) approach to simultaneously examine the relationship among the Metabolic Syndrome (MetSyn) and coronary artery calcification (CAC), a surrogate marker for sub-clinical atherosclerosis and coronary artery disease (CAD).

MATERIALS/METHODS

Data were derived from the Spokane Heart Study (SHS), a prospective study designed to examine the role of traditional and non-traditional biological, psychological, and behavioral risk factors predictive of CAC. Study participants included 434 non-clinical healthy volunteers (54% female, 46% male; mean age of 56 years) who were asymptomatic for CAD at enrollment and had complete data for the primary variables of interest (MetSyn components and CAC) during the data collection period (i.e., 2002-2006). A confirmatory factor analysis (CFA) was conducted on the MetSyn factor with the following indicator variables: body mass index, fasting glucose, high-density lipoprotein cholesterol, fasting triglyceride levels, and systolic blood pressure. SEM was used to test the theoretical model that the MetSyn is associated with CAC.

RESULTS

This study demonstrated that body mass index, fasting glucose, fasting triglyceride levels, HDL cholesterol, and blood pressure do cluster together under a single latent factor, and that this latent factor is associated with CAC.

CONCLUSIONS

Our results highlight the possibility that there is a common pathophysiological pathway that could explain the relationship between the MetSyn and CAD. Future studies should examine these relationships in a prospective fashion for early detection and prevention of CAD and to identify ideal time points for clinical intervention.