Duggan et al., 2018. Systemative review of pulmonary function and cognition in aging.

Duggan, E.C., Graham, R.B., Piccinin, A.M., Clouston, S., Muniz-Terrera, G., & Hofer, S.M. (2018). A systematic review of pulmonary function and cognition in aging. The Journal of Gerontology: Series B, gby128. DOI: https://doi.org/10.1093/geronb/gby128

Year: 
2018
Status: 
complete
Abstract: 

Background: Substantial research is dedicated to understanding the aging-related dynamics among individual differences in level, change, and variation across physical and cognitive abilities. Evaluating replicability and synthesizing findings has been limited by differences in measurements, samples, study design and statistical analyses which confound between-person differences with within-person changes. Here, we systematically reviewed longitudinal results on the aging-related dynamics linking pulmonary function and cognitive performance.

Methods: PRISMA guidelines were used to systematically review longitudinal studies of pulmonary function and cognition.

Results: Only four studies thoroughly investigating cognitive and pulmonary longitudinal associations (three or more measurement occasions) were identified. Expanded review criteria identified three studies reporting two measurement occasions, and seven studies reporting one measurement of pulmonary function or cognition and two or more measurements of the other. We identified numerous methodological quality and risk for bias issues across studies.

Conclusions: Despite documented correlational associations between pulmonary function and cognition, these results show there is very limited research thoroughly investigating their longitudinal associations. This highlights the need for longitudinal data, rigorous methodological design including key covariates, and clear communication of methods and analyses to facilitate replication across an array of samples. We recommend systematic study of outcome measures and covariates, inclusion of multiple measures (e.g., PEF, FEV1, and FVC), as well as application of the same analytic approach across multiple datasets.

Johnson et al., 2014. Modification of genetic influences on adiposity between 36 and 63 years of age by physical activity and smoking in the 1946 British Birth Cohort Study

Johnson, W., Ong, K. K., Elks, C. E., Wareham, N. J., Wong, A., Muniz-Terrera, G., & Hardy, R. (2014). Modification of genetic influences on adiposity between 36 and 63 years of age by physical activity and smoking in the 1946 British Birth Cohort Study. Nutrition & diabetes, 4(9), e136.

Year: 
2014
Status: 
complete
Abstract: 

Background: Previous studies reporting on the interaction between physical activity and genetic susceptibility on obesity have been cross-sectional and have not considered the potential influences of other lifestyle behaviours. The aim of this study was to examine modification of genetic influences on changes across age in adiposity during mid-adulthood by physical activity and smoking.

Methods: The sample comprised 2444 participants who were genotyped for 11 obesity variants and had body mass index (BMI), waist circumference-to-height ratio (WHtR), physical activity and smoking measures at 36, 43, 53 and 60–64 years of age. A genetic risk score (GRS) comprising the sum of risk alleles was computed. Structural equation models investigated modification of the longitudinal GRS associations by physical activity (active versus inactive) and smoking (non-smoker versus smoker), using a latent linear spline to summarise BMI or WHtR (multiplied by 100) at the age of 36 years and their subsequent rates of change over age.

Results: Physical activity at the age of 36 years attenuated the GRS associations with BMI and WHtR at the same age (P-interaction 0.009 and 0.004, respectively). Further, physical activity at the age of 53 years attenuated the GRS association with rate of change in BMI between 53 and 63 years of age (by 0.012 kg m−2 per year (95% confidence interval (CI): 0.001, 0.024), P-interaction 0.004). Conversely, smoking at the age of 43 years showed a trend towards augmenting the GRS association with rate of change in WHtR between 43 and 63 years of age (by 0.012 (95% CI: 0.001, 0.026), P-interaction 0.07). Estimated GRS effect sizes were lowest at all ages in the healthiest group (e.g., active non-smokers).

Conclusions: Healthy lifestyle behaviours appeared to attenuate the genetic influence on changes across age in BMI and central adiposity during mid-adulthood. An active lifestyle and not smoking may have additive effects on reducing the genetic susceptibility to obesity in adults.

Marioni et al., 2015. The epigenetic clock is correlated with physical and cognitive fitness in the Lothian Birth Cohort 1936

Marioni, R. E., Shah, S., McRae, A. F., Ritchie, S. J., Muniz-Terrera, G., Harris, S. E., Gibson, J., Redmon, P., Cox, S.R., Pattie, A., & Corley, J. (2015). The epigenetic clock is correlated with physical and cognitive fitness in the Lothian Birth Cohort 1936. International journal of epidemiology, 44(4), 1388-1396.

Year: 
2015
Status: 
complete
Abstract: 

Background: The DNA methylation-based ‘epigenetic clock’ correlates strongly with chronological age, but it is currently unclear what drives individual differences. We examine cross-sectional and longitudinal associations between the epigenetic clock and four mortality-linked markers of physical and mental fitness: lung function, walking speed, grip strength and cognitive ability.

Methods: DNA methylation-based age acceleration (residuals of the epigenetic clock estimate regressed on chronological age) were estimated in the Lothian Birth Cohort 1936 at ages 70 (n = 920), 73 (n = 299) and 76 (n = 273) years. General cognitive ability, walking speed, lung function and grip strength were measured concurrently. Cross-sectional correlations between age acceleration and the fitness variables were calculated. Longitudinal change in the epigenetic clock estimates and the fitness variables were assessed via linear mixed models and latent growth curves. Epigenetic age acceleration at age 70 was used as a predictor of longitudinal change in fitness. Epigenome-wide association studies (EWASs) were conducted on the four fitness measures.

Results: Cross-sectional correlations were significant between greater age acceleration and poorer performance on the lung function, cognition and grip strength measures (r range: −0.07 to −0.05, P range: 9.7 x 10−3 to 0.024). All of the fitness variables declined over time but age acceleration did not correlate with subsequent change over 6 years. There were no EWAS hits for the fitness traits.

Conclusions: Markers of physical and mental fitness are associated with the epigenetic clock (lower abilities associated with age acceleration). However, age acceleration does not associate with decline in these measures, at least over a relatively short follow-up.

Rast et al., 2014. The identification of regions of significance in the effect of multimorbidity on depressive symptoms using longitudinal data: an application of the Johnson-Neyman technique.

Rast, P., Rush, J., Piccinin, A., & Hofer, S. M. (2014). The identification of regions of significance in the effect of multimorbidity on depressive symptoms using longitudinal data: An application of the Johnson-Neyman technique. Gerontology60(3), 274-281.

Year: 
2014
Status: 
complete
Abstract: 

Background: The investigation of multimorbidity and aging is complex and highly intertwined with aging-related changes in physical and cognitive capabilities, and mental health and is known to affect psychological distress and quality of life. Under these circumstances it is important to understand how the effects of chronic conditions evolve over time relative to aging-related and end-of-life changes. The identification of periods in time where multimorbidity impacts particular outcomes such as depressive symptoms, versus periods of time where this is not the case, reduces the complexity of the phenomenon. 

Objective: We present the Johnson-Neyman (JN) technique in the context of a curvilinear longitudinal model with higher-order terms to probe moderatorst and to identify regions of statistical significance. In essence, the JN technique allows one to identify conditions under which moderators impact an outcome from conditions where these effects are not significant. 

Methods: To illustrate the use of the JN technique in a longitudinal sample, we used data from the Health and Retirement Study. Analyses were based on time-to-death models including participants who died within the study duration of 12 years. 

Results: Multimorbidity differentially affects rates of change in depression. For some periods in time the effects are statistically significant while in other periods the same effects are not statistically different from zero. 

Conclusion: The JN technique is useful to continuously probe moderating effects and to identify particular interactions with the model for time when certain effects are or are not statistically significant. In the context of multimorbidity this method is particularly useful for interpreting the complex interactions with differential change over time.

Clouston et al., 2015. Educational Inequalities in Health Behaviors at Midlife: Is There a Role for Early-life Cognition?

Clouston, S. A., Richards, M., Cadar, D., & Hofer, S. M. (2015). Educational inequalities in health behaviors at midlife: Is there a role for early-life cognition? Journal of health and social behavior, 56(3), 323-340.

Year: 
2015
Status: 
complete
Abstract: 

Education is a fundamental cause of social inequalities in health because it influences the distribution of resources, including money, knowledge, power, prestige, and beneficial social connections, that can be used in situ to influence health. Recent studies have highlighted early-life cognition as commonly indicating the propensity for educational attainment and determining health and age of mortality. Health behaviors provide a plausible mechanism linking both education and cognition to later-life health and mortality. We examine the role of education and cognition in predicting smoking, heavy drinking, and physical inactivity at midlife using data from the Wisconsin Longitudinal Study (N = 10,317), National Survey of Health and Development (N = 5,362), and National Childhood Development Study (N = 16,782). Adolescent cognition was associated with education but was inconsistently associated with health behaviors. Education, however, was robustly associated with improved health behaviors after adjusting for cognition. Analyses highlight structural inequalities over individual capabilities when studying health behaviors.

Robitaille, 2014. Physical Activity And Cognitive Functioning in the Oldest Old

Robitaille, A., Muniz, G., Lindwall, M., Piccinin, A. M., Hoffman, L., Johansson, B., & Hofer, S. M. (2014). Physical activity and cognitive functioning in the oldest old: within-and between-person cognitive activity and psychosocial mediators. European Journal of Ageing, 11(4), 333-347.

Year: 
2012
Status: 
complete
Presentation Citations: 

Robitaille, A., Muniz, G., Lindwall, M., Piccinin, A.M., Hoffman, L., Johansson, B., & Hofer, S.M. (October, 2012). Physical activity and cognitive functioning among older adults: Within- and between-person cognitive and psychosocial mediators.  Poster session presented at the 41th Annual Scientific and Educational Meeting of the CAG, Vancouver, BC.

Abstract: 

The current study examines the role of social contact intensity, cognitive activity, and depressive symptoms as within- and between-person mediators for the relationships between physical activity and cognitive functioning. All three types of mediators were considered simultaneously using multilevel structural equations modeling with longitudinal data. The sample consisted of 470 adults ranging from 79.37 to 97.92 years of age (M = 83.4; SD = 3.2) at the first occasion. Between-person differences in cognitive activity mediated the relationship between physical activity and cognitive functioning, such that individuals who participated in more physical activities, on average, engaged in more cognitive activities and, in turn, showed better cognitive functioning. Mediation of between-person associations between physical activity and memory through social contact intensity was also significant. At the within-person level, only cognitive activity mediated the relationship between physical activity and change in cognition; however, the indirect effect was small. Depressive symptomatology was not found to significantly mediate within- or between-person effects on cognitive change. Our findings highlight the implications of physical activity participation for the prevention of cognitive decline and the importance of meditational processes at the between-person level. Physical activity can provide older adults with an avenue to make new friendships and engage in more cognitive activities which, in turn, attenuates cognitive decline.

 

Rast & Hofer, 2014. Longitudinal design considerations to optimize power to detect variances and covariances among rates of change: Simulation results based on actual longitudinal studies

Rast, P., & Hofer, S. M. (2014). Longitudinal design considerations to optimize power to detect variances and covariances among rates of change: Simulation results based on actual longitudinal studies. Psychological Methods, 19(1), 133.

Year: 
2012
Status: 
complete
Presentation Citations: 

Hofer, S. M., & Rast, P. (October, 2012). Substantial power to detect variance and covariance among rates of change: Results based on actual longitudinal studies and related simulations. Paper presented at the annual meeting of the Society of Multivariate Experimental Psychology, Vancouver, BC

Abstract: 

We investigated the power to detect variances and covariances in rates of change in the context of existing longitudinal studies using linear bivariate growth curve models. Power was estimated by means of Monte Carlo simulations. Our findings show that typical longitudinal study designs have substantial power to detect both variances and covariances among rates of change in a variety of cognitive, physical functioning, and mental health outcomes. We performed simulations to investigate the interplay among number and spacing of occasions, total duration of the study, effect size, and error variance on power and required sample size. The relation between growth rate reliability (GRR) and effect size to the sample size required to detect power ≥ .80 was non-linear, with rapidly decreasing sample sizes needed as GRR increases. The results presented here stand in contrast to previous simulation results and recommendations (Hertzog, Lindenberger, Ghisletta, & von Oertzen, 2006Hertzog, von Oertzen, Ghisletta, & Lindenberger, 2008von Oertzen, Ghisletta, & Lindenberger, 2010), which are limited due to confounds between study length and number of waves, error variance with GCR, and parameter values which are largely out of bounds of actual study values. Power to detect change is generally low in the early phases (i.e. first years) of longitudinal studies but can substantially increase if the design is optimized. We recommend additional assessments, including embedded intensive measurement designs, to improve power in the early phases of long-term longitudinal studies.

Clouston et al., 2014. The Dynamic Relationship Between Physical Function and Cognition in Longitudinal Aging Cohorts

Clouston, S., Brewster, P., Kuh, D., Richards, M., Cooper, R., Hardy, R., Rubin, M., & Hofer, S. M. (2013). The dynamic relationship between physical function and cognition in longitudinal aging cohorts: A systematic review. Epidemiologic Reviews. Published online 2013 January 24.  doi: 10.1093/epirev/mxs004.

Year: 
2013
Status: 
complete
Abstract: 

On average, older people remember less and walk more slowly than do younger persons. Some researchers argue that this is due in part to a common biologic process underlying age-related declines in both physical and cognitive functioning. Only recently have longitudinal data become available for analyzing this claim. We conducted a systematic review of English-language research published between 2000 and 2011 to evaluate the relations between rates of change in physical and cognitive functioning in older cohorts. Physical functioning was assessed using objective measures: walking speed, grip strength, chair rise time, flamingo stand time, and summary measures of physical functioning. Cognition was measured using mental state examinations, fluid cognition, and diagnosis of impairment. Results depended on measurement type: Change in grip strength was more strongly correlated with mental state, while change in walking speed was more strongly correlated with change in fluid cognition. Examining physical and cognitive functioning can help clinicians and researchers to better identify individuals and groups that are aging differently and at different rates. In future research, investigators should consider the importance of identifying different patterns and rates of decline, examine relations between more diverse types of measures, and analyze the order in which age-related declines occur.