Considering the 24-Hour Activity Cycle in Older Adults

Abstract

Older adults are often advised to engage in more moderate-to-vigorous physical activity (MVPA). Although MVPA offers significant health benefits, focusing solely on MVPA may be difficult for many in this population due to their typically higher levels of sedentary behavior (SB). Increasing light-intensity physical activity (LIPA) can offer similar health benefits and be a more achievable starting point for inactive older adults. The 24-hour activity cycle provides a conceptual model that can assist healthcare providers in promoting physical activity. This model emphasizes the interaction between four key behaviors (i.e., sleep, sedentary behavior, LIPA, and MVPA) and presents a holistic approach to optimizing the balance of these activity behaviors. This article outlines strategies to help older adults increase their physical activity and reduce sedentary time within the 24-hour activity cycle, promoting sustainable, long-term behavior change in this population.

“In older adult patients, engaging in more PA of any intensity level will most likely cause a decrease in their SB.”

Introduction

Engaging in physical activity (PA) significantly helps to decrease an individual’s risk of various diseases and chronic conditions. In this issue, Piercy et al. discussed the importance of increasing moderate-to-vigorous intensity PA (MVPA) in older adults ¹ to decrease their risks of falls ² and enhance their ability to perform daily activities. ¹ While MVPA offers significant health benefits, increasing light-intensity physical activity (LIPA) can also improve various aspects of physical and cognitive health^3,4 and is a beneficial approach for this population. ⁵ This is particularly relevant for inactive individuals who spend large amounts of time in sedentary behaviors (SB), which significantly increase the risk of mortality and type 2 diabetes.^6-8 Despite the known benefits of LIPA and the negative impacts of SB, there are no specific guidelines or recommendations targeting these behaviors.^1,9 In this article, we discuss a new paradigm, the 24-hour activity cycle (24-HAC), that provides a more holistic model for healthcare providers when assisting older adult patients in reducing their SB.

The 24-Hour Activity Cycle

The 24-HAC consists of the interaction and integration of four behaviors: (1) sleep, (2) LIPA, (3) MVPA, and (4) SB.^5,10-13 This model delineates that these behaviors share a finite amount of time within a day, and all compete for time within the 24-HAC.^6,14 Per the 24-HAC, increasing PA requires replacing SB with MVPA or LIPA as multiple behaviors cannot co-occur, but can have an impact on one another. For example, engaging in LIPA can improve sleep quality. ¹⁵ In addition, long bouts of SB can have a negative impact on sleep quantity. ¹⁶ Despite knowing about the interactions between sleep and PA, many studies examine sleep, SB, LIPA, and MVPA individually. ¹⁷ The 24-HAC allows healthcare providers to holistically view an individual’s activity rather than only considering a single behavior.

The interactions between the 24-HAC behaviors have been widely studied and have been found impactful in developing intervention strategies for sustainable behavior change in youth.^18,19 As both PA and sleep are considerable concerns in youth, understanding the interactions of those behaviors with SB provides a clear direction for intervention. For instance, when SB was replaced with MVPA or sleep, youth fitness levels improved. ²⁰ In this case, replacing SB with sleep or PA was a beneficial trade. However, this model has yet to be used in older adults with most behaviors being examined independently. For example, LIPA has been shown individually to reduce all-cause mortality in adult women ²⁰ and SB has been shown to individually increase all-cause mortality.^6,7 Yet, the potential interaction between LIPA and SB remains unknown. ²¹ As the use of the 24-HAC has been effective for behavior change in youth, it can be a strong strategy to apply to older adult populations.

Sedentary Behaviors

For older adults, one of the main concerns is the long bouts of SB that occur.^22,23 On average, the general population spends 34% of their day sleeping, 39% engaged in SB, 24% engaged in LIPA, and 3% engaged in MVPA. ²⁴ Older adult populations have the highest amounts of SB, ²² creating an imbalance within their 24-HAC. Specifically, older adults in the United States tend to spend 60% of their day engaged in SB. ²³ The reduction of SB in this population should be a primary goal of individuals practicing lifestyle medicine.

Using the 24-HAC to reduce SB, means replacing SB with MVPA, sleep, or LIPA. An effective strategy to make this adjustment is to break up long bouts of SB with small bouts of LIPA throughout the day. ²⁵ As such, replacing as little as one hour of SB with LIPA has immense benefits, especially for inactive individuals.^6,12 Further, using this strategy provides increased adherence to PA as MVPA can be challenging for inactive older adults. Therefore, for sustainable behavior change in older adults with considerable SB, increasing PA should primarily come from trading off time spent engaged in SB for time engaged in LIPA, which may be a more achievable and lasting approach.^4,6,26

Strategies to Reduce Sedentary Behaviors

When advising older adult patients to increase their engagement in PA, a mistake may be made when immediately shifting to MVPA, especially in inactive individuals. Healthcare providers can use a stepwise approach to increase PA in this population. Specifically, having inactive older adult patients engage in LIPA and gradually increase their intensity level to MVPA overtime. Although the benefits of MVPA in this population are clear, ¹ focusing solely on increasing MVPA may be difficult for individuals who are already inactive and may struggle to meet MVPA recommendations. ²⁷ Even if they attempt to meet these guidelines, adherence may be challenging. This may explain the conflicting results in studies that explore the relationship between MVPA and SB in this population.^6,10,16,28

Consistent with the 24-HAC the majority of SB can be replaced by more active alternatives, even if they are non-exercise activities.^6,29 In other words, shifting less healthy behaviors into more active categories (e.g., LIPA) should be the focus of a stepwise approach. Slow and steady increases in PA engagement may be easier and more beneficial for older adults.^4,26 Specifically, activities of daily living may break up large bouts of SB, ⁶ as these are competing behaviors. ¹⁴ For example, watching TV can be broken up by short walks. These modifications are not an addition of activity but an adjustment to how time is spent within the 24-HAC.^10,12 Since SB compete for time within the 24-HAC of patients, it is important that healthier behaviors prevail in this competition and this will most likely be achieved through small, gradual adjustments for realistic and lasting behavior change.

Healthcare providers can identify key motivators for behavior change by starting discussions about their patients’ values regarding their health and life as a whole.^1,13,30 Supporting these values appropriately for positive behavior change may increase patient autonomy and motivation. ³⁰ For example, if an older adult patient wants to play with their grandchildren easily, healthcare providers can use this family value to support engagement in PA. If one of a patient’s values is cleanliness, engaging in regular household chores may easily compete for time spent in SB. ⁶ Again, framing changes in PA as a shift in one behavior (i.e., SB) into another, more healthful behavior (i.e., LIPA) will support lasting behavior change. Many activities of daily living that are considered LIPA (e.g., walking, gardening, cleaning, cooking) are proven competitors against SB and sedentary hobbies (e.g., watching TV, sitting).^1,6,10,13,31 Overall, any activity that competes with SB, regardless of intensity, is beneficial for inactive older adults.^1,6,13

In addition to competing behaviors, older adults also experience barriers to engaging in their community. ³² In order to mitigate these barriers, providers can create a list of free transportation options, routes to community engagement opportunities (e.g., how to get to the YMCA from the provider’s office), or events that may be walkable for their patients.^1,33 Specifically, engagement in community (e.g., YMCA, retirement homes) has been shown to increase PA engagement in older adult populations. ³³ Building personal relationships in the community can provide additional education, awareness, and planning for patients which can be beneficial to behavior change. ³¹ For example, older adults can utilize their community to decrease the time engaged in SB by meeting with others in their neighborhood to go for a casual walk a few days a week.^6,33 One excellent example of this is community gardening. ⁶ All of these activities have been shown to promote LIPA while reducing SB.

Conclusion

In older adult patients, engaging in more PA of any intensity level will most likely cause a decrease in their SB. This is important as replacing just one hour of time spent engaged in SB with a competing behavior, specifically LIPA for inactive individuals, can improve overall health.^6,12 The 24-HAC can assist healthcare providers in conceptualizing new opportunities for patients when monitoring their daily behaviors and understanding how their (in)active behaviors impact their health. ¹³ Healthcare providers can use the strategies to make recommendations for replacing SB with PA of any intensity within 24-HAC to support adult patients throughout the behavior change process. This model is consistent with creating slow, gradual changes in behavior and will ultimately foster long-term adherence.