Why sitting for long periods of time is bad for your health

Whether in the office, on the road, or at home, most of us sit down to do what we do well every day.

However, due to impaired vascular function, sitting in one place for long periods of time can increase the risk of serious health conditions, including cardiovascular disease and type 2 diabetes.

In 1953, epidemiologist Jeremy Morris found that London bus drivers were more likely to develop heart disease if they passed their bus conductors.

Given that the two groups of workers are demographically the same (in terms of age, gender and income range), why are there such stark differences?

Morris’ response was that the job of a bus conductor requires them to stand up and regularly climb the stairs of London’s iconic double-decker buses to sell tickets to passengers, while drivers remain seated for long periods of time.

This is a foundational study for research into the link between physical activity and coronary artery health.

London bus drivers will never again reign as kings in the way that Bifour did, but Morris’ results are more relevant than ever.

Since the COVID-19 pandemic, we have seen a major shift to working from home, which likely means we spend more time sitting.

Without the usual tasks of collecting water from a cooler or moving from one conference room to another, it’s easy for employees to remain seated at their desks for hours without getting up.

(But office culture changed our working lives so much as early as the 1980s that some researchers joked that humans had become Homo cedens (meaning “seated man”) rather than Homo sapiens.)

Sitting for long periods of time is a type of sedentary behavior, which is characterized by a significant decrease in energy expenditure when in a sitting or lying position.

Typical sedentary activities such as watching TV, playing games, driving, and desk work.

Sedentary behaviour is associated with an increased risk of cardiovascular disease, type 2 diabetes and premature death, and sitting time in particular has been found to be an independent risk factor for a range of health conditions.

In 2020, the World Health Organization proposed measures to reduce sedentary behavior.

The researchers noted that prolonged sitting is one type of typical sedentary behavior that shows a significant reduction in the energy expenditure required to sit or recline. Typical sedentary behaviors include watching television, playing games, driving, and desk work.

Sedentary behaviour is associated with an increased risk of cardiovascular disease, type 2 diabetes and premature death, and sitting time in particular has been identified as an independent risk factor for a range of health conditions.

For 2020, the World Health Organization has proposed measures to reduce sedentary behaviour.

Since 2010, researchers have been keen to point out the root cause of sedentary behaviour and lack of physical activity: even if you exercise enough every day, you still spend too much time sitting.

But for people who are physically inactive, the risks of sedentary behavior are even higher.

Needless to say, sitting for long periods of time aggravates vascular dysfunction, especially in the legs.

According to Sabi Pipo, the vascular system is responsible for maintaining blood and lymphatic fluids, which form part of the immune system, traveling through the blood vessels.

David Dunstan, a physiologist at the Physical Activity and Nutrition Institute at Deakin University in Melbourne, Australia, has extensively studied the effects of prolonged sitting and possible interventions.

“The main reason is that when you sit, your muscles become less active,” Dunstan says. “When you sit in a chair, the chair takes all the responsibility.”

The combined effects of decreased muscle activity, reduced metabolic demand, and gravity reduce blood flow to the leg muscles, causing blood to pool in the calf.

The biomechanics of sitting also reduce blood flow because the legs are usually bent.

Researchers suggest that sitting in one place for 120 to 180 minutes is not healthy.

Reduced leg muscle activity reduces metabolic demand. Since metabolic demand is the primary determinant of blood flow, leg blood flow also decreases. When sitting, blood pools in the calves when bending the legs, and one study of 21 young healthy volunteers found that calf circumference increased by about 1 cm (0.4 in) in 2 hours. Metabolic demand also reduces blood flow.

Normal blood flow creates friction, called arterial shear stress, against the endothelial cells of blood vessel walls. In response to this force, endothelial cells secrete vasodilators, such as adenosine, prostacyclin, and nitric oxide, to keep blood vessels well dilated and maintain the vascular system’s ability to self-regulate (commonly known as homeostasis).

However, when blood flow is reduced, shear stress is relieved and endothelial cells produce vasoconstrictors such as endothelin-1, which narrow the blood vessels. In a vicious cycle, vasoconstriction reduces blood flow further and increases blood pressure to maintain blood flow. Hypertension is one of the major risk factors for cardiovascular disease.

“That’s it [vascular dysfunction] “This is one potential mechanism,” Dunstan adds, “but the reality is that we can’t pinpoint the exact mechanism, and there may be multiple mechanisms.”

Although the underlying mechanism is hypothetical, recent studies support this theory. One study of 16 young, healthy men found that sitting for 3 hours increased leg blood volume, peripheral vascular resistance, diastolic blood pressure, and leg circumference. Another study found that prolonged sitting increases blood pressure. Researchers agree that 120 to 180 minutes of continuous sitting is probably the threshold for not spending too long in the same sitting position, but vascular dysfunction generally increases with increased sitting time.

Sitting for long periods of time after eating a high-fat meal can be harmful.

The musculoskeletal system can also be affected: prolonged sitting leads to loss of muscle strength, reduced bone density, and an increase in adipose tissue, both total and visceral fat.

In addition, sitting for long periods of time can be accompanied by physical discomfort, work stress, increased depression, and can even lead to bedsores.

Dr Dunstan, who also specialises in type 2 diabetes research, said sedentary behaviour after meals leads to higher blood sugar and insulin levels. Reduced insulin sensitivity and impaired vascular function both contribute to an increased risk of cardiovascular disease and type 2 diabetes.

Society is encouraging people to be more sedentary. As efficiency increases, we don’t need to move around as much. – Benjamin Gardner

Despite these well-known potential consequences, why do we still sit for long periods of time, and how can we break the habit?

“I think people are becoming more sedentary because of what society is encouraging,” he said.

“It’s not that anyone is sitting there on purpose; it’s just that we’re more efficient now and we don’t need to move around as much,” said Benjamin Gardner, a social psychologist specializing in habitual behavior at the University of Surrey, who studies why people sit for long periods of time.

In 2018, Gardner and his colleagues found that unique social barriers exist to encourage people to stand up in meetings.

“We recommend giving this a try. [standing up] “We had three different meetings, and interviewed them after each one to see how they would do, and the results surprised us,” Gardner said. “After one formal meeting, they felt they were like sand.”

Getting up often and taking a short walk or climbing the stairs can also help.

Wearable technology can also help remind us to move: One promising new study shows that wearable devices called accelerometers can provide 24-hour data on an individual’s behavioral patterns, such as sitting, standing, sleeping and exercising.

As Dunstan pointed out earlier, the device allows you to customize the amount of time you spend sitting and standing to suit you, and automatically sends you reminders when you’ve been sitting too long.

But using the technology is not without its drawbacks: some people have complained about not being able to or sending messages.

Above all, Gardner and his colleagues recommend frequently switching between sitting and standing positions.

The premise of breaking up sitting time by simply standing up is simple, but the health benefits are huge, especially for less active people.

Wheelchair users and people with limited mobility can benefit from certain adaptive exercises.

For many of us, modern life and work can make it difficult to avoid sedentary behaviour, but making small changes to your daily routine, like stretching more, fidgeting or standing up to make a cup of tea, can help break the habit.