Physical Activity Helps Preserve “Executive Function” into Old Age: Study

This study was originally published in Frontiers in Neursocience, August 23, 2016.

Authors:

  • 1Health Psychology, Institute of Applied Health Sciences, University of Aberdeen, Aberdeen, UK
  • 2Behavioural Science Centre, Stirling Management School, University of Stirling, Stirling, UK
  • 3UCD Geary Institute, University College Dublin, Dublin, Ireland

Physically active lifestyles and other health-enhancing behaviors play an important role in preserving executive function into old age. Conversely, emerging research suggests that executive functions facilitate participation in a broad range of healthy behaviors including physical activity and reduced fatty food, tobacco, and alcohol consumption. They do this by supporting the volition, planning, performance monitoring, and inhibition necessary to enact intentions and override urges to engage in health damaging behavior. Here, we focus firstly on evidence suggesting that health-enhancing behaviors can induce improvements in executive function. We then switch our focus to findings linking executive function to the consistent performance of health-promoting behaviors and the avoidance of health risk behaviors. We suggest that executive function, health behavior, and disease processes are interdependent. In particular, we argue that a positive feedback loop may exist whereby health behavior-induced changes in executive function foster subsequent health-enhancing behaviors, which in turn help sustain efficient executive functions and good health. We conclude by outlining the implications of this reciprocal relationship for intervention strategies, the design of research studies, and the study of healthy aging.

Introduction

Physical activity has been described as “the best buy in medicine” (Loprinzi, 2015). Having an active lifestyle not only reduces the risk of chronic conditions (Warburton et al., 2006), it also helps preserve cognitive function (Sofi et al., 2011) and in particular, higher level “executive” function (EF) into old age (Colcombe and Kramer, 2003), and by doing so may enhance subsequent activity levels and foster a range of other health protective behaviors, producing long-run health benefits (Loprinzi, 2015). In the same way, engagement in other health behaviors could yield similarly reciprocal cognitive and behavioral benefits and reduce the incidence of chronic disease.

 KEY CONCEPT 1. What is Executive Function?
EF is an umbrella term for the related but distinct processes involved in the effortful control of goal directed behavior. Largely mediated by the prefrontal cortex, EF has been summarized as “.… the co-ordinated operation of various processes to accomplish a particular goal in a flexible manner” (Funahashi, 2001) and encompasses three main factors:

• mental flexibility/set shifting (strategically shifting attention between goals and flexibly adapting thinking to suit the situation),

• monitoring and updating working memory (evaluating and updating goal relevant information held in mind), and

• inhibition of prepotent responses (suppressing inappropriate, dominant, or habitual responses when necessary).

 In this review we propose that a set of self-reinforcing positive feedback loops link health-protective behaviors and EF. First, we provide an overview of research linking physical activity and other health-enhancing behaviors to increases in EF. Second, we examine emerging evidence pointing to EF as a key driver of the successful adoption and maintenance of physically active lifestyles and health promoting behavior. Third, we propose an integrated reciprocal account whereby EF and health behavior are linked through a feedback loop that could confer substantial health benefits over time. Finally, we outline implications for intervention strategies and study design.

In the context of cognitive function, higher-level EFs are of critical importance as they provide the self-regulatory resources needed to effectively plan and execute goal-directed behaviors (Hofmann et al., 2012b). Specifically, the EFs are the higher-order cognitive processes involved in the planning, initiation, sequencing and monitoring of complex goal directed behavior (<a href="http://journal.frontiersin.org/article/10.3389/fnins.2016.00386/full#B115" onclick="__gaTracker('send', 'event', 'outbound-article', 'http://journal.frontiersin.org/article/10.3389/fnins.2016 discover here.00386/full#B115', 'Royall et al., 2002');">Royall et al., 2002; Lezak et al., 2004) and can be thought of collectively as the processes which enable top-down control of behavior, thoughts, and emotion. While the concept is notoriously difficult to define, there is broad agreement that the term covers three distinct but overlapping processes: mental flexibility, working memory, and inhibition (Miyake et al., 2000; Miyake and Friedman, 2012).

Over the lifespan, the combined influence of these three facets of EF allows health promoting goals to be pursued despite the presence of distraction, tempting situational cues, and visceral desires (Hall and Marteau, 2014). EF typically declines in old age, potentially compounding age related declines in health as EF plays an important role in carrying out tasks including chronic illness management (Tomlin and Sinclair, 2016) and in allowing health-enhancing behaviors to be enacted and health-damaging behaviors to be resisted (Hall et al., 2008a; Williams and Thayer, 2009). Perhaps as a result, those with better EF tend to avoid chronic illness and live longer even following the diagnosis of a chronic illness (Duff et al., 2009; Hall et al., 2009, 2010). Fully understanding the cognitive factors associated with positive health behaviors and with healthy aging in general is vitally important in the context of our rapidly aging population. By 2050, the World Health Organization anticipates that 1.5 billion people will be aged 65 or over (World Health Organisation, 2011) so ensuring that health is preserved into old age is a key goal for health scientists.

In addition to influencing health outcomes, EFs are themselves influenced by health-related behaviors and the resulting disease processes in several ways. For example EF is less efficient in individuals who exercise less than others (Colcombe and Kramer, 2003), who are obese (Debette et al., 2011) or who show evidence of systemic inflammation (Komulainen et al., 2007; Trollor et al., 2012). We suggest that positive feedback loops exist whereby EF sustains health protective behaviors which in turn protect cognitive function and physical health into old age (McMinn et al., 2013). In our previously published paper (Daly et al., 2015), the catalyst for this review, we provided a demonstration of this idea in the area of physical activity, showing not only that higher levels of EF lead to increased future levels of physical activity, but also that higher levels of physical activity contribute to future improvements in EF.

This original paper was written in the context of (a) a substantial evidence base linking physical activity level to improvements in executive functioning, and (b) suggestions from the literature that the opposite may also be the case i.e., that efficient EF may facilitate future engagement in physical activity. Our study was designed to test this by modeling the directionality of the physical activity—EF relationship.

Using data collected from 4555 older adults over 6 years (4 study waves) of the English Longitudinal Study of Aging (ELSA), we ran three separate sets of analyses. Firstly, we examined the cross-sectional association between physical activity and executive functioning for individuals across the four study waves using multilevel modeling adjusting for age, sex, education, wealth, and long-standing illness. Next we examined how changes in physical activity related to simultaneous changes in executive functioning by conducting a fixed effects analysis to test whether within-person variation in physical activity was associated with within-person variation in executive functioning. By examining within-person variation in this way, any effects of non-observed time-invariant confounders (i.e., factors such as genetics, early adversity etc.) are essentially ruled out as they would not be expected to vary within people over time. Finally, we used longitudinal multilevel modeling to test whether physical activity at one point in time could be used to predict changes in EF and whether the efficiency of EF could predict subsequent engagement in physical activity.

These analyses revealed that physical activity and EF were closely interlinked and that the association between the two remained after controlling for demographic and health characteristics. Furthermore, we demonstrated that dynamic within-person changes in EF corresponded with parallel changes in physical activity, largely ruling out the possibility that non-observed, time-invariant confounders had produced the association. Critically, we found evidence that the relationship between physical activity and EF is bidirectional. Those with poor EF showed subsequent decreases in their rates of participation in physical activity and older adults who engaged in sports and other activities involving physical exertion tended to retain high levels of EF over time.

In the present review we describe in more detail the evidence supporting the existence of a bidirectional, reciprocal link between physical activity and EF and expand this idea to incorporate other health protective behaviors.

Read full study here.