Overcoming Sedentary Behavior

KEY POINTS

  • • Sedentary behavior, particularly at high levels (more than seven hours of sitting or lying down during waking hours per day), is associated with increased risk of all-cause mortality and mortality from cardiovascular disease and Type 2 diabetes, as well as some cancers.
  • • Regular, moderate to vigorous physical activity can offset many of the increased risks associated with sedentary behavior.
  • • Benefits of moderate to vigorous physical activity are particularly strong for individuals with high levels of sedentary behavior and who are currently inactive.

INTRODUCTION

Considerable research has emerged over the past decade in the area of sedentary behavior (1). Good data are now available to suggest that sedentary behavior increases the risk of a variety of conditions including coronary heart disease (CHD) and Type 2diabetes (T2DM). Sedentary behavior is defined as “any behavior which is characterized by an energy expenditure of 1.5 METs or less, while in a sitting, reclining, or lying posture (2).”

In addition to its negative association with health outcomes, sedentary behavior is highly prevalent in the United Statespopulation. Data from the U.S. National Health and Nutrition Examination Survey (NHANES) indicate that children and adults in the US spend approximately 7.7 hours per day (55% of monitored time) being sedentary (3). Thus, reversing this sedentary behavior trend in the United Statescould generate significant health improvements. The current chapter examines sedentary behavior and its relationship to various health issues using the framework established by the Physical Activity Guidelines for Americans 2018 Advisory Committee Scientific Report (1).

SEDENTARY BEHAVIOR AND ALL-CAUSE MORTALITY

The PAGA 2018 Scientific Report rated the evidence for a relationship between the greater amount of time in sedentary behavior and all-cause mortality as strong (1). Based on a total of nine systematic reviews and meta-analyses that consisted of twenty original studies, a significant relationship between sedentary behavior and all-cause mortality was revealed (4-11). In addition, some of the studies showed that TV viewing or screen time were also related to all-cause mortality (12, 13). There also appears to be a dose-response relationship between sedentary behavior and allcause mortality (7,9). The studies that have been reviewed showed that for every one hour increase in sitting time, or for more than seven hours a day sitting, there were dose-related responses to increased sedentary behavior and all-cause mortality (7). A similar response was revealed between TV viewing and all-cause mortality where, once again, using different criteria, a dose-response relationship was found (9).

An inverse relationship exists between the amount of moderate to vigorous physical activity and sedentary behavior when it comes to all-cause mortality (10, 11). The adverse effects on all-cause mortality from sedentary behavior are strongest amongst people who have low amounts of physical activity. This relationship is illustrated in Figure 14.1.

Individuals who were found to have greater than seven hours of sedentary behavior and also low levels of moderate to vigorous physical activity substantially increased their risk of all-cause mortality. Individuals who accumulated between 16 and 30 MET hours per week of moderate intensity physical activity substantially low'ered their risk of all-cause mortality, even if they were sedentary for more than seven hours per day (11).

To put this in perspective, the PAGA 2018 recommends between 10 and 15 MET hours per week of physical activity. There are additional benefits for individuals

Hours per Day Sitting

FIGURE 14.1 Relationship between sitting and all-cause mortality, stratified by amount of moderate-to-vigorous physical activity.

(Adapted from data found in Ekelund et al. 2016. 2018 Physical Activity Guidelines Advisory Committee. 2018 Physical Activity Committee Scientific Report. Washington, DC US Department of Health and Human Services; 2018. Part F, Chapter 2, Sedentary Behavior.)

who achieve greater than 30 MET hours per week, although the incremental benefit is relatively small compared to the benefit of meeting the recommended dosage of moderate to vigorous physical activity outlined in the PAGA 2018 document. Individuals who have sedentary occupations (such as office work), thus, will particularly benefit from following the guidelines for moderate to vigorous physical activity on a weekly basis.

There has also been some suggestion that taking breaks in sedentary behavior may reduce its adverse health effects related to all-cause mortality. Some research exists in this area, although further research is required to determine whether or not periodic breaks in sedentary behavior will ameliorate some of the adverse health effects of high levels of this behavior.

The relationship between sedentary time and moderate to vigorous physical activity is depicted graphically in Figure 14.2 (1).

Daily Sitting Time

Moderate-to-Vigorous Physical Activity

Risk of all-cause mortality decreases as one moves from gray to black.

FIGURE 14.2 Relationship among moderate-to-vigorous physical activity, sitting time, and risk of all-cause mortality.

(Adapted from data found in Ekelund et al. 2016. 2018 Physical Activity Guidelines Advisory Committee. 2018 Physical Activity Committee Scientific Report. Washington, DC US Department of Health and Human Services; 2018. Part F, Chapter 2, Sedentary Behavior.)

As this figure shows, the more sedentary time an individual participates in, the more the risk of all-cause mortality, unless they are physically active. Physical activity, as shown in this figure, largely can ameliorate the increased risk of sedentary behavior.

SEDENTARY BEHAVIOR AND CARDIOVASCULAR DISEASE MORTALITY

The risk of mortality from cardiovascular disease (CVD) and its relationship to sedentary behavior is very similar to the relationship between sedentary behavior and all-cause mortality (6, 10). The PAGA 2018 Scientific Report documented that increased physical activity of ameliorated increases in sedentary behavior. In addition, there was strong evidence that there was a dose-response relationship. Thus, the more physical activity an individual participates in, the more the increased risk of sedentary behavior is reduced. As depicted in Figure 14.3 sedentary behavior of greater than five hours a day starts to significantly increase the risk of cardiovascular disease and it is further increased if sedentary behavior is greater than seven hours per day (1).

Hours per Day Sitting

FIGURE 14.3 Relationship between sitting and cardiovascular disease mortality, stratified by amount of inoderate-to-vigorous physical activity.

(Adapted from data found in Ekelund et al. 2016. 2018 Physical Activity Guidelines Advisory Committee. 2018 Physical Activity Committee Scientific Report. Washington, DC US Department of Health and Human Services; 2018. Part F, Chapter 2, Sedentary Behavior).

SEDENTARY BEHAVIOR AND CANCER MORTALITY

The PAGA 2018 Scientific Report judged the evidence between a direct relationship with the amount of time spent in sedentary behavior and higher mortality rates from cancer as limited (10). While a number of studies have reported a significant association, the results were inconsistent. (One study showed a relationship for women only; another one showed one only for television viewing, but not sitting; and one showed a relationship only in current smokers.) Furthermore, cancer is a heterogeneous disease and many of the risk factors for cancer mortality are clearly affected by cancer screening, treatment availability, and efficacy.

The PAGA 2018 Scientific Report also concluded that there was insufficient evidence available to determine whether or not the relationship between sedentary behavior and cancer mortality was modified by physical activity. Evidence among specific types of cancer was moderate (14). For example, moderate level physical activity in sedentary individuals was related to decrease in added risk for breast cancer, ovarian cancer, prostate cancer, and lung cancer.

SEDENTARY BEHAVIOR AND TYPE 2 DIABETES

There is strong evidence that a significant relationship exists between the amount of time spent in sedentary behavior and risk of Type 2 diabetes (T2DM) (4-6, 10, 13). The issue of whether or not there is a dose-response relationship, however, is only supported by limited evidence. The issue of TV viewing appeared to be different between individuals who were active and inactive. Active individuals did not experience elevated risk of T2DM, whereas, inactive participants who reported high TV viewing were at increased risk for Type 2 diabetes (T2DM). More detail about physical activity and T2 DM may be found in Chapter 5.

SEDENTARY BEHAVIOR AND WEIGHT STATUS

Limited evidence supports a relationship between sedentary behavior and weight status (4, 5). The studies that are available in this area showed considerable variations among results. With regard to adiposity, once again studies are quite heterogeneous, allowing only limited support for the concept that sedentary behavior is associated with adiposity.

SEDENTARY BEHAVIOR AND MODERATE TO VIGOROUS PHYSICAL ACTIVITY

There is some evidence that moderate to vigorous physical activity lowers the risk of sedentary behavior (ll). It is important to note, however, that the relative reductions in risk are most significant for those who are the most sedentary. In general, the same relationship holds for CVD mortality as well as for all-cause mortality with significant interaction between level of physical activity and sedentary behavior. Again, the most significant benefits come to those who are the most sedentary. When the data concerning sedentary behavior are stratified by level of sitting or TV viewing, the relationships are still quite similar with the amount of sedentary behavior, sitting or TV viewing significantly increasing the risk of all-cause mortality, while the level of moderate to vigorous physical activity lowers the added risk in a dose-response manner.

PUBLIC HEALTH IMPACT

High levels of sedentary behavior are associated with increases in all-cause mortality, mortality from CVD and T2DM. High levels of sedentary behavior are also associated with moderate increases in certain cancers such as those of breast, ovary, and prostate.

There is good evidence that moderate or vigorous physical activity can lower the increased risk associated with sedentary behavior. This is particularly striking in individuals who have the highest level of sedentary behavior. For all of these reasons, physicians should assess the level of sedentary behavior in every patient and. if needed, recommend increased levels of moderate to vigorous physical activity. The public health impact on such changes could be very significant.

CONCLUSIONS

Both children and adults in the United Stateshave become increasingly sedentary. The average child or adult in the United States spends 7.7 hours per day being sedentary. This includes screen time, watching TV, and other tasks sitting or lying down. These levels of sedentary behavior have now been clearly demonstrated to increase all-cause mortality and mortality from CVD, T2DM. and some cancers. Levels of moderate to vigorous physical activity can offset the increased risk of sedentary behavior. This is particularly true for individuals who have the highest levels of sedentary behavior and are also inactive. For all of these reasons, physicians should assess the level of sedentary behavior in every patient and, if necessary, recommend increased levels of moderate to vigorous physical activity to lower the increased risk of sedentary behavior.

CLINICAL APPLICATIONS

  • • Sedentary behavior, particularly at levels of greater than seven hours per day, is associated with increased risk of all-cause mortality.
  • • Sedentary behavior is also associated with increased risk of CVD and T2DM as well as some cancers.
  • • Moderate to vigorous physical activity may offset the adverse consequences of sedentary behavior, particularly in individuals who have high levels of sedentary behavior and are also currently inactive.
  • • Physicians should assess levels of sedentary behavior in every patient and recommend increased levels of moderate or vigorous physical activity, if necessary.

REFERENCES

  • 1. 2018 Physical Activity Guidelines Advisory Committee. 2018 Physical Activity Guidelines Advisory Committee Scientific Report. Washington. DC: U.S. Department of Health and Human Services. 2018. Part F. Chapter 2. Sedentary Behavior.
  • 2. Tremblay M. Aubert S. Barnes J, et al. SBRN terminology consensus project participants. Int J Behav Nutr Phys Act. 2017;14(l):75.
  • 3. Matthews C. Chen K, Freedson P, et al. Amount of time spent in sedentary behaviors in the United States, 2003-2004. Am J Epidemiol. 2008:167(7):875-881.
  • 4. Proper K, Singh A. van Mechelen W, et al. Sedentary behaviors and health outcomes among adults: a systematic review of prospective studies. Am J Prev Med. 2011:40(2): 174-182.
  • 5. Thorp A. Owen N. Neuhaus M. et al. Sedentary behaviors and subsequent health outcomes in adults a systematic review of longitudinal studies, 1996-2011. Am J Prev Med. 2011:41(2):207-215.
  • 6. Wilmot E, Edwardson C. Achana F. et al. Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis. Diabetologia. 2012:55( 11):2895-2905.
  • 7. Chau J. Grunseit A. Chey T. et al. Daily sitting time and all-cause mortality: a meta-analysis. PLoS One. 2O13;8(l l):e80000.
  • 8. de Rezende L, Rey-Lopez J, Matsudo V, et al. Sedentary behavior and health outcomes among older adults: a systematic review. BMC Public Health. 2014:14:333. doi:10.1186/1471- 2458-14-333.
  • 9. Sun J. Zhao L, Yang Y. et al. Association between television viewing time and all-cause mortality: a meta-analysis of cohort studies. Am J Epidemiol. 2015:182(11):908—16.
  • 10. Biswas A. Oh P, Faulkner G. et al. Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: a systematic review and meta-analysis. Ann Intern Med. 2015:162(2): 123—132.
  • 11. Ekekmd U. Steene-Johannessen J. Brown W, et al. Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women. Lancet. 2016;388(10051):1302—1310.
  • 12. George S. Smith A. Alfano C. et al. The association between television watching time and allcause mortality after breast cancer. J Cancer Surviv. 2013;7(2):247-252.
  • 13. Grontved A. Hu F. Television viewing and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality: a meta-analysis. JAMA. 2011;305(23):2448—2455.
  • 14. Seguin R. Buchner D. Liu J, et al. Sedentary behavior and mortality in older women: the Women’s health initiative. Am J Prev Med. 2014:46(2): 122—135.
 
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