Introduction:
The prevalence of sedentary lifestyles poses a significant challenge to public health, particularly among older adults. The shift towards more desk-bound and screen-centric routines has given rise to a myriad of health concerns, ranging from cardiovascular issues to cognitive decline. Recognizing the impact of a sedentary lifestyle on the well-being of older individuals is paramount for devising effective interventions to manage and mitigate these risks. The nature of sedentary behavior plays a crucial role, with television watching consistently linked to poorer health outcomes. This could be attributed to television being a passive, sedentary behavior often accompanied by snacking. Research on the most detrimental type of sedentary behavior yields varied findings. Optimal health outcomes are associated with short sedentary bouts interspersed with intermittent physical activity, light physical activity, muscle training, intermittent interruptions during work-related sedentary periods, and rest combined with physical activity.
What Is a Sedentary Lifestyle?
A sedentary lifestyle is a behavior in which the individual engages in insufficient physical activity, negatively impacting health. Despite this, the health risks associated with sedentary behaviors remain unknown. Limited spaces for exercise influence it, increased occupational sedentary behaviors and the widespread use of television and video devices.
The impact of a sedentary lifestyle on the human body involves various mechanisms, including the reduced activity of lipoprotein lipase, impaired metabolism of lipids and carbohydrates, decreased cardiac output, and activation of the sympathetic nervous system, leading to reduced insulin sensitivity and vascular function.
Additionally, changes in the insulin-like growth factor axis and sex hormone levels elevate the risk of hormone-related cancers. Extended sedentary time disrupts the gravitostat, affecting the body’s weight homeostasis and contributing to weight gain, adiposity, and chronic inflammation – known risk factors for cancer. The adverse effects of sedentary behaviors encompass increased all-cause mortality, cardiovascular disease mortality, cancer risk, and the likelihood of metabolic disorders, musculoskeletal issues, depression, and cognitive impairment.
What Physiological Changes Occur During a Sedentary Lifestyle?
The specific mechanisms underlying the diverse adverse effects of sedentary behavior on the human body are not fully understood. However, several hypotheses have been proposed to comprehend the overall impact of sedentary behavior on physiological processes. Some of the effects involve:
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Metabolic Dysfunction: Sedentary lifestyles are linked to metabolic dysfunctions, including elevated plasma triglycerides and reduced insulin sensitivity. Lipoprotein lipase (LPL) concentration, a cellular-level protein, plays a role in these metabolic processes. Low LPL concentration is associated with decreased plasma HDL cholesterol levels, contributing to conditions such as severe hypertension, diabetes-induced dyslipidemia, metabolic disorders related to aging, metabolic syndrome, and coronary artery diseases. Physical inactivity further diminishes LPL activity in skeletal muscles, signaling impaired lipid metabolism.
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Bone Mineral Density Reduction: Sedentary behavior is associated with decreased bone mineral density. Studies on healthy adults undergoing 12 weeks of bed rest showed a one to four percent reduction in mineral density in the lumbar spine, femoral neck, and greater trochanter. The balance between bone resorption and deposition influences this relationship, with evidence suggesting that bed rest elevates bone resorption markers without influencing bone formation markers.
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Vascular Health Impact: Limited evidence suggests that sedentary behavior may negatively affect vascular health. A study on healthy women undergoing 56 days of head-down bed rest revealed a decrease in endothelium-dependent vasodilation and an increase in endothelial cell damage. Notably, these alterations in vascular function were prevented through aerobic exercise and muscle training.
What Is the Impact of Sedentary Lifestyle on Older Adults?
1. Sedentary Lifestyles, Mortality, and Morbidity (Cardiovascular Diseases and Other Causes):
A sedentary lifestyle is strongly linked to increased risks of cardiovascular diseases (CVD), diabetes mellitus (DM), cancer, and premature mortality. Both total daily sedentary time and television viewing time correlate with higher all-cause mortality risk. Individuals with over 10 hours of daily sitting have a significantly increased risk of all-cause mortality. Television viewing for more than 6 hours daily is associated with a twofold higher risk than watching less than 2 hours, emphasizing the impact of sedentary behavior on overall mortality.
Sedentary time, encompassing sitting, television or screen viewing, and leisure time while sitting, is independently associated with all-cause mortality, CVD incidence or mortality, certain cancers (breast, colon, colorectal, endometrial, and ovarian), and type 2 DM. Notably, the adverse effects are more pronounced among those with minimal physical activity. High physical activity slightly offsets the risk for all-cause mortality, emphasizing the importance of addressing sedentary behavior alongside physical activity.
2. Sedentary Lifestyles and Metabolic Diseases:
- Diabetes Mellitus: Increased sedentary time correlates with higher prevalence and risk of type 2 DM.
- Hypertension: Sedentary behavior influences blood pressure through various mechanisms, including reduced metabolic demands, systemic blood flow, and increased sympathetic nervous system activity, contributing to hypertension.
- Dyslipidemia: Sedentary behaviors lead to metabolic dysfunction characterized by elevated blood triglyceride levels, reduced HDL-cholesterol levels, and diminished insulin sensitivity. Physical activity has a contrasting effect, negatively associating with blood triglyceride levels.
- Obesity: Sedentary time correlates significantly with waist circumference and metabolic risk scores, independent of Moderate-to-Vigorous Physical Activity (MVPA). Increased sedentary time is associated with weight gain, and breaking sedentary habits can aid in obesity treatment.
3. Sedentary Lifestyles and Cancer Risk:
Sedentary behavior is closely linked to cancer prevalence and mortality. Prolonged sitting increases the risks of colorectal, endometrial, ovarian, and prostate cancers. Increased total sitting time and television viewing time positively correlate with colon and endometrial cancer risks. Sedentary behavior induces metabolic dysfunctions and chronic inflammation, contributing to hormone-related cancers.
4. Sedentary Lifestyles and Osteoporosis: Sedentary behavior negatively correlates with bone mineral density, particularly in adult women, impacting the total femur and all hip sub-regions. The sedentary behavior's duration, rather than the frequency, influences bone mineral density.
5. Sedentary Lifestyles and Musculoskeletal Diseases: Extended sedentary time is correlated with chronic knee pain, with individuals exceeding 10 hours of daily sedentary time experiencing higher incidence. Increased physical activity is associated with less chronic knee pain, emphasizing reducing sedentary time.
6. Sedentary Lifestyles and Other Diseases:
- Depression: Mentally passive sedentary behaviors, such as television viewing, correlate positively with depression risks, while mentally active sedentary behaviors show no significant correlation. The mechanism involves reduced social interactions and limited time for physical activities.
- Cognitive Function: The relationship between sedentary behavior and cognitive function is uncertain. Replacing sedentary time with moderate-to-vigorous physical activity and sleep improves cognitive function in older adults, highlighting the potential benefits of reducing sedentary behavior for cognitive health.
Conclusion:
A sedentary lifestyle presents a spectrum of detrimental health effects, encompassing heightened risks of all-cause mortality, Cardiovascular Disease (CVD) mortality, cancer, and various metabolic and musculoskeletal diseases, including Diabetes mellitus (DM), hypertension, dyslipidemia, knee pain, and osteoporosis. These negative health impacts' severity unequivocally escalates with prolonged daily sedentary times. Hence, it is imperative to minimize sedentary time as much as possible. In situations where extensive exercise is not feasible, incorporating light physical activity is beneficial, and individuals are encouraged to increase their physical activity levels as circumstances permit gradually.
