Investigating Moderator Hypotheses in Aging Research: Statistical, Methodological, and Conceptual Difficulties with Comparing Separate Regressions

Physical Activity, Occupational Stress, and Cardiovascular Risk Factors in Law Enforcement Officers: A Cross-sectional Study

OBJECTIVE

This cross-sectional study aimed to assess the interrelationship between leisure-time physical activity (LTPA), occupational stress, and cardiovascular disease (CVD) risk factors in law enforcement officers (LEOs).

METHODS

A total of 229 LEOs completed a survey assessing their LTPA level, occupational stress, and CVD risk factors.

RESULTS

After adjusting for age and sex, physically inactive LEOs are more likely to have one or more CVD risk factors. While high occupational stress was associated with greater odds of CVD risk factors in physically inactive LEOs, stress was not significantly associated with the prevalence of CVD risk factors in active LEOs.

CONCLUSIONS

Our results suggest that occupational stress is associated with the prevalence of CVD risk factors in LEOs. Nevertheless, LTPA might have the potential to mitigate the impact of occupational stress on CVD risk factors.

Chronic Pain and Friendship among Middle-Aged and Older U.S. Adults

OBJECTIVES

This study examines how chronic pain affects friendship in later life. We test whether onset of pain leads to social network activation, as suggested by research on other health conditions (Latham- Mintus, Forth.), or whether pain-an unverifiable and often stigmatizing condition-functions as a "threat to the social self" (Karos et al., 2018).

METHODS

Using longitudinal data from the Health and Retirement Study (HRS; N=4,598; 2006/2008 as Time 1 and 2010/2012 as Time 2), we conducted OLS regressions with the lagged dependent variable approach to assess how new-onset chronic pain predicted (a) respondents' number of close friends and (b) their frequency of in-person meetings with friends, controlling for sociodemographic variables and health conditions.

RESULTS

New-onset severe pain predicted a decrease in number of friends. New-onset moderate pain, in contrast, predicted more friends and more frequent in-person meetings. (Findings were significant or marginally significant depending on model specifications.) Mild pain showed no significant association with either outcome. Pain had a greater effect on men's friendship outcomes than women's.

DISCUSSION

The effects of chronic pain on later-life friendships appear to depend on pain severity, and to differ between men and women. Onset of severe pain serves as a "threat to the social self," while onset of moderate pain contributes to social network activation; both associations are significantly more pronounced among men. These findings highlight the complex associations between health and social outcomes.

The Role of Marital Quality in Physical Health During the Mature Years

Objective: This study examined the role of marital quality in the physical health of mature adults. Method: Participants were from the National Survey of Midlife Development in the United States aged 50+ years who were in their first marriage. Five dimensions of marital quality and four indicators of physical health were used. Results: Regression analyses indicated that marital quality indices accounted fora significant amount of explained variance in physical health. Most notably, higher levels of negative spousal behaviors uniquely contributed to physical health, predicting more physical symptoms, chronic health problems, and physical disability, and poorer perceived health. Discussion: The occurrence of negative spousal behaviors was consistently associated with poorer physical health. The negativity effect observed regarding the costs and benefits of social support in general also applies to the context of marriage in that negative spousal behaviors outweigh positive spousal behaviors in contributing to mature adults’ physical health.

Psychosocial Resources as Moderators of the Impact of Spousal Dementia Caregiving on Depression

This study examines the relationship of personal mastery and perceived emotional support to depressive symptoms for spousal dementia caregivers (CGs) and noncaregiver (NCG) spouses. Although it is well known that caring for a spouse with dementia is stressful and that personal mastery and emotional support may reduce stress, the authors hypothesize that these resources are more important for reducing stress in the difficult situation of dementia care than in everyday life for older persons. In bivariate comparisons, CG levels of perceived support and mastery were lower and depression was higher than for NCGs. Consistent with prior research, a hierarchical multiple regression with combined data shows that CG status was a significant predictor of depressive symptoms. A significant interaction of CG status with personal mastery indicates greater impact of mastery on depression among CGs than among NCGs. This unique finding strongly supports interventions focusing on enhancement of mastery among spousal CGs.

Body-related sport and exercise motives and disturbed eating attitudes and behaviours in adolescents

Motives underlying sport and exercise involvement have recently been hypothesized as potential factors influencing the positive association between sports/exercises involvement and disturbed eating attitudes and behaviours (DEAB) among adolescents. Nevertheless, very few studies have examined this hypothesis or the moderating role of gender, context of practice, performance levels and sport type on these relationships. In this study, these questions were addressed among 168 male and 167 female French adolescents involved in various types, contexts and performance levels of sport and exercise. Participants were asked to indicate their main motives for involvement in sport practice and to self-report DEAB (generic DEAB, vomiting-purging behaviours, and eating-related control) on a French adaptation of the Eating Attitudes Test-26. The results shared positive associations between body-related sport and exercise motives and most of the DEAB subscales. Furthermore, they show that the relationship between body-related sport and exercise motives and Vomiting-Purging Behaviours differs according to involvement in individual and competitive sports and exercises.

Moderation analysis using a two-level regression model

Moderation analysis is widely used in social and behavioral research. The most commonly used model for moderation analysis is moderated multiple regression (MMR) in which the explanatory variables of the regression model include product terms, and the model is typically estimated by least squares (LS). This paper argues for a two-level regression model in which the regression coefficients of a criterion variable on predictors are further regressed on moderator variables. An algorithm for estimating the parameters of the two-level model by normal-distribution-based maximum likelihood (NML) is developed. Formulas for the standard errors (SEs) of the parameter estimates are provided and studied. Results indicate that, when heteroscedasticity exists, NML with the two-level model gives more efficient and more accurate parameter estimates than the LS analysis of the MMR model. When error variances are homoscedastic, NML with the two-level model leads to essentially the same results as LS with the MMR model. Most importantly, the two-level regression model permits estimating the percentage of variance of each regression coefficient that is due to moderator variables. When applied to data from General Social Surveys 1991, NML with the two-level model identified a significant moderation effect of race on the regression of job prestige on years of education while LS with the MMR model did not. An R package is also developed and documented to facilitate the application of the two-level model.

Demystifying moderators and mediators in intellectual and developmental disabilities research: a primer and review of the literature

BACKGROUND

Intellectual and developmental disability (IDD) researchers have been relatively slow to adopt the search for moderators and mediators, although these variables are key in understanding how and why relationships exist between variables. Although the traditional method of causal steps is useful for describing and understanding moderators and mediators, it is not sufficient for statistical analysis.

METHODS

The theoretical and statistical processes of evaluating moderators and mediators are explained in terms familiar to IDD psychologists, using examples from IDD literature. Moderator and mediator analyses in five leading IDD journals are assessed for patterns of usage.

RESULTS

Although the number of publications in the past decade exceeds previous years, the field is still behind others in both the quantity and quality of the use of moderators and mediators.

CONCLUSION

The field as a whole will advance if the recent theoretical and technical advances outlined in this paper are employed.

The role of age and social motivation in developmental transitions in young and old adulthood

Two diary studies investigated the role of social approach and avoidance motivation in important developmental transitions in young and old adulthood. Study 1 comprised a sample of young adults (N = 93, M = 21.5 years) who moved out of their parental homes. The sample of Study 2 consisted of older adults (N = 69, M = 76.95 years) who moved into senior housing. In both studies, participants reported their habitual social approach and avoidance motives as well as their daily social experience and subjective well-being over the course of 2 weeks. In line with the literature, social approach motives and age were related to higher subjective well-being, whereas social avoidance motives were negatively associated with subjective well-being. Time since the transition was an important moderator of the association between social avoidance motives and negative outcomes. With increasing time from the transition, the negative effects of social avoidance motives decreased. The positive effects of social approach motives remained fairly stable over time. Importantly, age did not moderate any of the associations between social motivation and outcomes. Results are discussed in terms of transition-related instability and age-related stability.

Allostatic load in an environmental riskscape: the role of stressors and gender

Stressors are theorized to be associated with higher allostatic load (AL), a concept of physiological wear measured as a composite of physical biomarkers. Risk of high AL may vary by gender and may be intensified in places with significant environmental risks, otherwise known as 'environmental riskscapes'. Yet, no study has examined the relationship between stressors, gender, and allostatic load in an environmental riskscape. Using primary data collected in a sample (N=1072) exposed to various environmental and social stressors, we find that long-term residence in Texas City (30 or more years), residential proximity to petrochemical plants, perceived poor neighborhood conditions, and daily hassles are associated with higher allostatic load components. Variation in AL differs by gender and the types of biomarkers examined. Gender moderates the effect of length of residence in Texas City on cardiovascular health risk. We discuss our findings in light of current research on stressors, gender, allostatic load, and double jeopardy within environmental riskscapes.

Quantifying and Testing Indirect Effects in Simple Mediation Models When the Constituent Paths Are Nonlinear

Most treatments of indirect effects and mediation in the statistical methods literature and the corresponding methods used by behavioral scientists have assumed linear relationships between variables in the causal system. Here we describe and extend a method first introduced by Stolzenberg (1980) for estimating indirect effects in models of mediators and outcomes that are nonlinear functions but linear in their parameters. We introduce the concept of the instantaneous indirect effect of X on Y through M and illustrate its computation and describe a bootstrapping procedure for inference. Mplus code as well as SPSS and SAS macros are provided to facilitate the adoption of this approach and ease the computational burden on the researcher.

Increase in antidepressant medication in the US adult population between 1990 and 2003

BACKGROUND

The rate of antidepressant treatment in the US has significantly increased in the past decade. There are, however, concerns about undertreatment among traditionally underserved groups and overtreatment in less severely ill individuals. This study examines trends in the prevalence of antidepressant drug treatment in two US general population surveys.

METHODS

The prevalence of antidepressant treatment within a 12-month period was compared in the US National Comorbidity Survey (1990-1992) and the National Comorbidity Survey-Replication (2001-2003). Variations in trends across groups were examined using bivariate and multivariate logistic regression models.

RESULTS

The rate of antidepressant drug treatment increased more than four times between early 1990s and early 2000s. The trend was similar across sociodemographic groups. Younger adults, men and racial/ethnic minorities continued to receive antidepressant treatment at a lower rate compared to middle-aged adults, women and non-Hispanic whites, respectively. The rate of antidepressant treatment increased more in the group of less severely ill individuals than in those with more severe psychopathology.

CONCLUSIONS

Sociodemographic disparities in antidepressant treatment persisted over the last decade in the US, lending support to concerns about undertreatment among traditionally underserved groups, whereas the greater increase in the rate of antidepressant treatment in the less severely ill group lends support to concerns about antidepressant overtreatment in this population.

Utility of traditional and alternative EMG-based measures of fatigue during low-moderate level isometric efforts

Traditional electromyographic (EMG) measures (e.g., amplitude, mean and median frequencies of the power spectra) have demonstrated inconsistent abilities in monitoring localized muscle fatigue at relatively low effort levels. In the present study, several alternative EMG-based fatigue indices were evaluated, derived using a logarithmic representation of the power spectrum, the fractal dimension of the raw signal, and a Poisson distribution fit to the power spectrum. These methods, along with traditional approaches, were applied to EMG data obtained from three separate experiments. In the first two experiments, 24 participants performed sustained isometric shoulder abductions and torso extensions at 30% of maximum voluntary strength (MVC). In the third experiment, another group of 12 participants performed similar shoulder exercises at 15% and 30% MVC, with repeatability assessed at 15% MVC. Both traditional and alternative EMG measures were analyzed for their 'utility', in terms of sensitivity to fatigue, variability, repeatability, and predictive ability. Results demonstrated that parameters derived from fractal analysis and the Poisson distribution demonstrated high utility. These alternative approaches appear promising as fatigue indices for low level isometric tasks.

Combining temporal-envelope cues across channels: effects of age and hearing loss

The goal of this study was to examine the ability to combine temporal-envelope information across frequency channels. Three areas were addressed: (a) the effects of hearing loss, (b) the effects of age and (c) whether such effects increase with the number of frequency channels. Twenty adults aged 23-80 years with hearing loss ranging from mild to severe and a control group of 6 adults with normal hearing participated. Stimuli were vowel-consonant-vowel syllables. Consonant identification was measured for 5 conditions: (a) 1-channel temporal-envelope information (minimal spectral cues), (b) 2-channel, (c) 4-channel, (d) 8-channel, and (e) an unprocessed (maximal spectral cues) speech condition. Performance of listeners with normal hearing and listeners with hearing loss was similar in the 1-channel condition. Performance increased with the number of frequency channels in both groups; however, increasing the number of channels led to smaller improvements in consonant identification in listeners with hearing loss. Older listeners performed more poorly than younger listeners but did not have more difficulty combining temporal cues across channels than in a simple, 1-channel temporal task. Age was a significant predictor of nonsense syllable identification, whereas amount of hearing loss was not. The results support an age-related deficit in use of temporal-envelope information with age, regardless of the number of channels.