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The common activity that’s worsening your health

The common activity that’s worsening your health

Alistair Gardiner|March 30, 2021

In today’s working world, many of us are sitting most of the day in front of our computer—especially with the shift to telemedicine appointments. Research indicates that those in office-based professions spend 70%-85% of their workday seated—and all of that sitting is detrimental to our cardiovascular, metabolic, and mental health, according to a recent study published in BMC Musculoskeletal Disorders.Man holding his lower back

Sitting for prolonged periods of time is worse for your health than you think.

The pandemic has made matters worse. Reports point to decreases in physical activity in general since the virus prompted lockdown restrictions and stay-at-home orders. One study found that more than 40% of US adults were sitting for more than 8 hours a day during April 2020. 

Does so much sitting really translate to worse health? How does it affect the body and the mind? Here’s how this sedentary lifestyle changes us, according to the latest research.ADVERTISEMENT -SCROLL TO KEEP READING

The health impacts of being sedentary  

Evidence suggests that not using our bodies for long periods of time takes a toll on our well-being. Prolonged periods of sitting have been linked to metabolic disorders like increased blood pressure, high blood sugar, obesity, and high cholesterol levels, according to the Mayo Clinic. Extensive periods of sitting are also associated with an increased risk of cardiovascular disease and cancer mortality. 

A review published in The Lancet found that those who sit for more than 8 hours a day with no physical activity had a mortality risk similar to that caused by obesity and smoking.  

According to the BMC article, prolonged sitting is also associated with type 2 diabetes incidence and all-cause mortality. Other studies have demonstrated that sitting can lead to musculoskeletal problems such as neck and shoulder pain.

Why you should get moving

The good news? Countering these negative effects is simple, at least in theory. You need to stay active. The authors of the aforementioned Lancet study analyzed data from more than 1 million subjects and found that those who engage in 60-75 minutes of moderate-to-intense physical activity a day effectively ameliorated the adverse outcomes of prolonged sitting. 

Other research has found that even just replacing some of your sitting time with standing can help. One review published in Mayo Clinic Proceedings examined nine clinical trials focused on the effects of standing rather than sitting on factors including fasting blood glucose, fasting insulin, and lipid levels; blood pressure; body fat mass; weight; and waist circumference. The average difference in standing time between the control group and the intervention group was 1.33 hours per day. While they didn’t observe major differences in every outcome measured, researchers did find that those who spent more time standing had significantly lower body fat mass values and fasting blood glucose levels. They concluded that replacing a few hours of sitting with standing could be used as an adjunctive intervention to help mitigate cardiovascular risk factors and assist in preventing diabetes. 

Similarly, the BMC review concluded that breaking up periods of prolonged sitting with standing or light exercises could help mitigate the ill effects of too much sitting. The review examined the range of physiological mechanisms affected by sitting for too long and hypothesized that some of these factors may be affecting cognitive function.

Researchers analyzed studies that showed how long periods of sitting increase hyperglycemia, autonomic stability, inflammation, adverse hormonal changes, and restrictions in cerebral blood flow. Together, the researchers argued, these factors may negatively affect cognitive performance. 

Intermittent standing or low-to-moderate physical activity may improve cognitive function by mitigating the adverse vascular and hormonal changes that result from too much sitting, they found. Breaking up prolonged periods of sitting was shown to have positive effects on postprandial hyperglycemia, insulin resistance, inflammatory markers, the regulation of hormones like cortisol, and cortical and peripheral arterial blood flow. The authors linked all of these mechanisms to possible improvements to cognitive function. 

Movement guidelines

To mitigate the risks of too much sitting, experts advise following the US government’s Physical Activity Guidelines for Americans, which states that everyone should get a minimum of 150 minutes of physical activity per week. 

Beyond this, we should take a break from sitting every 30 minutes and find ways to fit in more standing and walking throughout the day, according to the Mayo Clinic. Tips include: Stand while you talk on the phone or watch TV; try working at a standing desk; hold “walking meetings” with colleagues, rather than sitting around a conference table; or (for the adventurous) set up a treadmill at your workstation, so you can stay active throughout the day.

If you need an extra push, you might find some useful tips in the findings of a study published in BMJ, which analyzed the impact of a multicomponent intervention to reduce sitting time. Subjects received a height-adjustable workstation, informational seminars and training sessions, and even a vibrating timer-cushion to remind the subjects that they’d been sitting for too long. Researchers found that, after 1 year, those in the intervention group were sitting for an average of 83 minutes fewer per day than the control group. Additionally, subjects in the intervention group reported improvements in job performance, work engagement, occupational fatigue, daily anxiety, and quality of life.

For those who find themselves sitting for prolonged periods, the evidence suggests you should probably swap out your current workstation for a standing desk, and if you’ve got a day of pencil-pushing and keyboard tapping ahead, make sure you take regular breaks.

For more ideas on combating sedentary behavior, click here

Withdrawal of hormone therapy and increased risk of cardiovascular disease

. 2016 Jun;19(3):249-51. doi: 10.1080/13697137.2016.1175237. Epub 2016 Apr 14.

Withdrawal of hormone therapy and increased risk of cardiovascular disease

A Pines  1 Affiliations


Many menopause specialists follow the principle of prescribing postmenopausal hormone therapy (HT) for the shortest duration needed, in order to decrease the risk of some related serious adverse effects, such as breast cancer. Based on several large studies, it seems, however, that withdrawal of HT may be associated with immediate, though small increased risk of coronary heart disease and stroke. Cessation of HT correlates with increased risk of fractures as well. This information should be relayed to hormone users while discussing the continuation of HT with their health-care provider, but, since the potential cardiovascular harm is actually very small, it should not deter symptomatic women from using HT when needed.

We know hand dryers can circulate germs through the air. Why are they still used everywhere?


We know hand dryers can circulate germs through the air. Why are they still used everywhere?

March 29, 2021 1.20pm AEDT


  1. Christian Moro Associate Professor of Science & Medicine, Bond University
  2. Charlotte Phelps PhD Student, Bond University

Disclosure statement

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.


Bond University

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Airborne contaminants, dirty toilet seats, mould and mildew: long before the coronavirus pandemic came around, the hygiene-focused among us knew public washrooms are grimy places.

Most adults visit the bathroom around 8-10 times a day. With an average hand-drying time of 30 seconds, we can expect between 4-5 minutes of daily dryer use per person (and more for people with an overactive bladder or similar disorders).

In an attempt to facilitate the hand washing process, are hand dryers adding to the filth by blowing contaminants around? And if so, why are they still common?

The need to dry

Drying hands is an essential part of the hand washing process. Wet hands can further the spread of microbes, since moisture facilitates their transfer from the skin to other surfaces.

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Compared to shaking your hands dry after a wash, using an air dryer or paper towel greatly reduces the number of surface bacteria that remain.

Warm air dryers remove moisture from the hands through evaporation, while jet air dryers remove it by using sheer force to disperse the droplets into the air.

Bathroom wall with both paper towels and air dryer.
Some bathrooms offer both paper towels and air dryers. Should you prioritise one of them? Christian Moro

It’s worth remembering hand dryers don’t create microbes and there’s usually only minimal bacteria on their nozzles, too. In many cases air dryers can even be fitted with filters that help clean and remove contaminants from the air.

Put a lid on it!

Nonetheless, while dryers themselves aren’t necessarily unclean, their forced air can help circulate bacteria around the space. This is why the main focus should be on preventing bacteria from surfaces ever becoming aerosolised (entering the air) in the first place.

If a toilet’s lid is left open when it’s flushed, a fine aerosolised mist of microbes enters the air. And this cloud of faecal matter can spread over an area of up to six square metres.

Research has shown even after flushing many times, a toilet can continue to emit contaminants into the air. In other words, a person infected with a virus could be spreading these germs for several hours after visiting the bathroom.

Public washrooms can therefore act as reservoirs for especially nasty bacteria, such as those which are resistant to antibiotics.

So are paper towels the solution?

Read more: Coronavirus and handwashing: research shows proper hand drying is also vital

Problems with paper

Paper towels remove water by absorption and take contaminants with them when they’re binned. However, they can cause plumbing problems if flushed down the toilet, which require time and money to fix.

Additionally, paper towels need to be continuously purchased, restocked and disposed of as waste — all of which leads to increased costs. In a worst-case scenario towels may run out, prompting people to exit without drying their hands at all.

Granted, in a hospital setting a dryer’s forced air may move microbes onto items handled by health professionals and patients, such as phones or stethoscopes. So paper towels may be a more suitable option here.

But they still don’t provide an entirely sterile environment and can be contaminated by microbes circulating in the area.

Toilet paper stuck to shoe leaves bathroom
If contaminated paper towels are discarded on the floor, people stepping on them can transfer germs via their shoes to outside areas. Shutterstock

Weighing the environmental impact

Although hand dryers do produce carbon emissions, studies have shown warm air dryers (which rely on evaporation) generate up to 70% more emissions than newer, fast jet dryers (which force out a rush of cold air).

Environmentally speaking, warm air dryers and paper towels perform roughly the same, on average.

Using recycled paper towels doesn’t seem to help much, either. This is because they can’t be recycled further, due to chemicals added to increase their absorptive properties as well as the overall energy required to manufacture them.

In the US, around six million tonnes of paper towels end up in landfill each year.

The dry debate continues

Some research has concluded paper towels make a more hygienic method for drying hands. Meanwhile, aggressive jet hand dryers seem to have shown the greatest potential for dispersing bacteria and particles over wider distances.

But there isn’t a clear winner in practise. A recent critical review concluded there wasn’t enough research weighing up both options and that until more robust studies were conducted, evidence-based public policy recommendations couldn’t be made.

This echoes both the World Health Organisation’s and Centre for Disease Control’s hesitance to offer recommendations for whether drying hands with air dryers is more or less effective than using paper towels.

Read more: The great bathroom debate: paper towel or hand dryer?

Tips for a healthy bathroom regimen

While hand dryers can circulate contaminants around a space, the aim should be to stop germs from becoming aerolised in the first place. If the contaminants aren’t in the air to begin with, their dispersion from hand dryers is less of a worry.

No standing on the toilet seat.
Common sense goes a long way in bathroom hygiene. Shutterstock

Health education on this front is important. Simple recommendations include:

  • closing the toilet lid before flushing
  • wearing a mask where recommended or required, especially for those who have respiratory tract symptoms or a cough
  • coughing or clearing your throat directly into a tissue and immediately throwing it in the bin
  • washing your hands regularly with soap and water and not forgetting to dry them, as wet hands are more likely to spread bugs and diseases.

In areas where infection control and prevention are paramount, such as hospitals or food production areas, measures such as increased airflow and air filters can also help.

The bottom line

Using paper towels comes with recurring costs, logistical problems and environmental considerations. Meanwhile, air dryers can further circulate vapourised bacteria.

Managers of public washrooms have much to consider when deciding which method of hand drying to provide. In some scenarios, hand dryers do present as a better option, which is why we continue to see them in public washrooms.

Regardless of what option you choose, don’t forget drying is an essential part of the hand-washing process. Both air dryers and paper towels are, by a long way, better than using nothing at all.

Yes, COVID vaccines are front and centre. But don’t forget about your flu shot


Yes, COVID vaccines are front and centre. But don’t forget about your flu shot

March 24, 2021 5.51am AEDT


  1. Ian Barr Deputy Director, WHO Collaborating Centre for Reference and Research on Influenza

Disclosure statement

Ian Barr has shares in an influenza vaccine producing company. The Centre receives funding from the Australian Government and from other industry based sources.


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As the nights begin to close in and the temperatures cool, it’s clear winter is approaching again.

With the winter season comes the risk of the usual winter lurgies, most of which result from respiratory infections. Some of the usual suspects include rhinoviruses (the common cold), RSV (respiratory syncytial virus), and influenza.

This year, of course, we’re also contending with the possibility that SARS-CoV-2 (the virus that causes COVID-19) could escape from its quarantine status and circulate alongside these other viruses.

We don’t know yet how the winter season will play out in terms of respiratory viruses. But one important way we can prepare for it is by getting a flu vaccine.

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What will winter bring?

In 2020 there was a paucity of seasonal winter viruses. Only rhinoviruses circulated widely, while the others were either vastly reduced (for example, we saw a very minimal flu season) or very delayed (RSV circulated later than usual in some states until spring or even summer).

So what’s going to happen in 2021? Will it be similar to 2020, or will it be like 2019, which saw very high levels of influenza? Or perhaps something completely different?

We simply don’t know for sure. With COVID-related restrictions having eased in all Australian states and territories — albeit to varying degrees — people are free to move around, come together in crowds, and attend schools, universities and offices.

These activities promote the transmission of respiratory viruses, which explains why we saw such different trends in the usual winter lurgies last year, when we were mixing much less.

Read more: RSV is a common winter illness in children. Why did it see a summer surge in Australia this year?

But the virus circulation needs to start from somewhere. While some viruses are happy to circulate domestically, like rhinoviruses and adenoviruses, others, like influenza, are largely transported into the country each year. So it’s possible that if Australia’s international borders remain closed through winter, we may again have a less serious flu season in 2021.

On the other hand, if borders are opened and the flu does take hold, people might have reduced immunity to the viruses given the missed season last year, and be more susceptible.

A hand holds a thermometer. There is a cup of tea and tablets on a table in the background.
Last winter we saw significantly fewer cases of the flu than usual. Shutterstock

A vaccine is your best bet

In the face of this uncertainty, the usual adage prevails: “prevention is better than cure”. The best measure we can take is to get our influenza vaccine.

The flu vaccines available in Australia in 2021 under the National Immunisation Program are:

  • for children aged six months to five years — Vaxigrip Tetra® (Sanofi) and Fluarix® Tetra (GSK)
  • for children and adults aged five to 64 years — Vaxigrip Tetra®, Fluarix® Tetra and Afluria® Quad (Seqirus)
  • for adults aged 65 and over — Vaxigrip Tetra®, Fluarix® Tetra, Afluria® Quad and Fluad® Quad (Seqirus).

The Fluad® Quad vaccine, which is slightly different and more potent than the others, is the preferred vaccine for the over-65 age group. It contains a component called an adjuvant, which helps boost the immune response in elderly people.

This season’s flu vaccines are made up of four different viruses — two influenza A types and two influenza B types. The 2021 vaccines have two changes (both in the influenza A types) from the 2020 influenza vaccines.

It’s very hard to predict in advance which strains will circulate, but the World Health Organization provides guidance on this every year, and recommends which components of the vaccine should be updated accordingly.

All the influenza vaccines used in Australia are inactivated virus vaccines, meaning the virus contained in the vaccine doesn’t replicate, so you can’t get the flu from the vaccination.

Read more: Flu vaccines are updated every year. We can learn from this process as we respond to COVID variants

In addition to the flu vaccines under the National Immunisation Program, a new vaccine called Flucelvax® Quad (Seqirus) is available through retail outlets, like pharmacies, for people aged nine years and older.

This vaccine is the first influenza vaccine available in Australia which has been produced entirely in cell culture, rather than chickens eggs. This new vaccine may have some benefits over the traditional egg-based vaccines for certain people, for example those with severe egg allergies.

How effective are flu vaccines?

Flu vaccines are only moderately effective at preventing infection with influenza. On average, they offer around 60% protection across the population, although rates can often be higher in children.

While this is lower than we’d like, it’s the best measure we currently have to protect us from influenza infections. There’s also evidence it reduces the more severe consequences of being infected, such as being hospitalized or dying.

Scientists are continuing to work on new flu vaccines that may offer greater protection.

The corridor of a COVID-19 vaccination centre on the Gold Coast.
The COVID vaccine rollout might somewhat complicate the flu vaccine rollout this year. HEALTH QLD/AAP

The practicalities

This year’s vaccines are already becoming available through pharmacies and some GP clinics, and will be available under the National Immunisation Program from GPs and other providers, such as workplace immunisation programs, in April.

The flu season generally starts in earnest around June, so it’s reasonable to get your vaccine any time between now and then.

Under the National Immunisation Program, some groups are eligible to receive the influenza vaccine for free. These include:

  • adults 65 and older
  • all Aboriginal and Torres Strait Islander Australians six months and older
  • children aged six months to five years
  • pregnant women
  • people with certain medical conditions.

For people who don’t fall into these groups, the vaccine costs as little as A$14.99.

Read more: You can’t get influenza from a flu shot – here’s how it works

Influenza vaccines are being rolled out this year alongside the COVID-19 vaccines. With both programs operating at the same time, there may be some confusion and logistical challenges.

The Australian Technical Advisory Group on Immunisation have recommended a 14-day gap between the COVID and flu vaccinations, regardless of which one you have first. This is something both individuals and providers will need to keep in mind and will mean some extra planning this year.


I will continue to work as normal through the lock down. Telephone consults are encouraged for those concerned about visiting the Medical Centre. The staff and doctors have all had their first vaccine against COVID.

Impact of progesterone on skin and hair in menopause

Impact of progesterone on skin and hair in menopause – a comprehensive review

S. Gasser , K. Heidemeyer , M. von Wolff & P. Stute Received 27 Mar 2020, Accepted 09 Oct 2020, Published online: 02 Feb 2021


In clinical practice, micronized progesterone (MP) is frequently recommended to treat signs and symptoms of skin and hair aging in menopausal women. The aim of this comprehensive review was to evaluate whether topically or systemically applied MP may effectively prevent or slow down signs of skin and hair aging. Three out of six identified studies reported an impact of MP on skin aging markers in menopausal women. Of these, two studies reported a benefit: one for topically applied MP, another for systemically applied combined menopausal hormone therapy (MHT) comprising MP as progestogen for endometrial protection. Tolerability and safety of MP were good. However, there was no study investigating the impact of MP on menopausal scalp hair. In conclusion, delay of skin aging comprises lifestyle adjustment, antioxidants, and several esthetic procedures. In menopausal women, MHT displays beneficial effects on skin aging. There is poor quality but promising scientific evidence for MP displaying anti-aging skin effects in menopausal women. However, good quality studies are needed.

Covid Vaccine.

I had my Astra- Zeneca Covid Vaccine shot yesterday. Twenty four hour later I have had minimal side effects. A bit tired, and some muscle aches. Women tend to react more than men, and the staff were vaccinated earlier this week and had more pain, swelling at the injections side, fatigue and some headaches. Those symptoms are receding now. My view is that this is a small price to pay to avoid getting Covid. In future you are most likely not going to be able to travel anywhere without a signed certificate of having completed a course of one of the Covid Vaccines.

Best preventive ‘medicine,’ and it’s not what you think

ew AJM article cites best preventive ‘medicine,’ and it’s not what you think

Alistair Gardiner|March 16, 2021

When it comes to preventive medicine, you might think of healthy behaviors like eating well, taking vitamins, getting enough sleep, or seeing your doctor or dentist for regular check-ups. So it may surprise you to learn that a recent article in the American Journal of Medicine (AJM) has identified the best preventive “medicine” for a variety of maladies.Man running with dog in park

Here’s one surprising form of preventive “medicine” every doctor should know about.

The “medicine” in question? Dogs. Yes, you read that right. Dogs. 

According to the article, our pet dogs offer us more than companionship and joy—they provide a whole range of health benefits. 

Our furry friends became the first animals we domesticated between 20,000-40,000 years ago; today, there are roughly 89 million pet dogs in the United States. According to a 2019/2020 pet owner survey, more than 63 million households in the United States have at least one dog.   

And that’s a healthy trend, according to research. 

“Whether [dogs] are terrestrial angels without wings (as many believe) or a highly-evolved species of wolf with an instinctive love of humans, their well-documented mental and physical health benefits should strongly encourage physicians to recommend dog ownership to their patients,” the author wrote.

Evidence is robust enough that the CDC has jumped on the canine bandwagon, noting that having a dog is linked to lower cholesterol levels, lower blood pressure, decreased triglyceride levels, less loneliness, and more. 

Here’s a look at the research behind why dog ownership is great for physical and mental health.


Sometimes dogs leave us no choice but to get up and go—and such physical activity can be great for our health. According to the AJM article, more than half of all preventable deaths result from poor lifestyle choices, and lack of physical inactivity is at the top of that list.

Research shows that exercising regularly can significantly reduce all-cause mortality, cardiovascular disease, and cancer mortality. Working out has been shown to help combat or prevent 26 chronic conditions, including hypertension, type 2 diabetes, cognitive decline, and others. 

Evidence indicates that dog ownership is strongly associated with lowering risks of cardiovascular conditions and mortality. In short, having a dog means more frequent walks. 

“Credible evidence demonstrates that owning a dog, with its walking obligation, is strongly associated with a lower risk of cardiovascular conditions and death (hazard ratio = 0.77, 95% confidence interval = 0.73-0.80),” wrote the author. 

In fact, studies show that dog owners are four times more likely to achieve the 150 minutes per week of physical activity that’s recommended as a minimum by the US government’s Physical Activity Guidelines for Americans.  

Past studies have reached the same conclusion. One review published in the Journal of Physical Activity and Health examined 29 studies and found that roughly two-thirds of dog owners walk an average of 160 minutes per week and a median of four times per week. Another study, published in BMC Public Health, suggested that those who have a dog walk an average of 22 minutes more per day than those who don’t—and they sit around less, too. 


Rates of some immune-related conditions (from asthma to multiple sclerosis) are still on the rise, likely as a result of improvements in sanitation, vaccines, and antibiotics—eliminating some of the microorganisms that have kept our immune systems in balance. According to the author of the AJM article, this appears to have resulted in a trend of overstimulated immune systems, which mistakenly attack proteins like pollen or peanuts, or even the body’s own tissues. As it stands, around one in five children live with asthma and allergies, or autoimmune disorders like Crohn disease, lupus, MS, and others. 

Dogs, however, could be the antidote to this. The author noted that dogs share a number of “favorable microorganisms,” which live on their fur and in their mouths, with children. Exposure to these microbes can help protect against allergic diseases. The article cites a study that examined children living on farms, in close proximity to bacteria in barns and on animals, and found that these kids were far less likely to develop allergies or autoimmune diseases in comparison to nonrural children. 

Mental health

Even prior to the lockdowns and social restrictions of the coronavirus pandemic, mental health issues were prevalent, the author noted. Before COVID-19, the National Academies of Sciences, Engineering and Medicine reported that more than a third of adults 45 years and older felt lonely, and a quarter of those 65 or older were considered socially isolated. These conditions don’t just impact people’s emotional states, they can impact physical health, too. According to the AJM article, “loneliness and social isolation are significantly associated with a 50% increased risk of dementia, 29% increased risk of heart disease, 32% increased risk of stroke, and a greater risk of all causes of premature death.”

The companionship of living with a dog can help mitigate this. The author noted that dog ownership is associated with reduced rates of depression and can particularly help for subgroups like single individuals, homeless youth, older individuals who’ve lost a spouse, and elderly women.

For example, service dogs have been assigned to those with post-traumatic stress disorder (PTSD), and there’s plenty of evidence that this practice helps, the author wrote. PTSD can lead to depression, substance abuse, and suicidal tendencies, and it impacts roughly 14% of all military veterans returning from war zones. Research has shown that having a service dog can significantly reduce the symptoms of PTSD and can lead to increased social interaction in general. 

Blood clots: five reasons they may happen

Blood clots: five reasons they may happen

March 17, 2021 4.45am AEDT •Updated March 17, 2021 5.12am AEDT


  1. Adam Taylor Professor and Director of the Clinical Anatomy Learning Centre, Lancaster University

Disclosure statement

Adam Taylor is affiliated with the Anatomical Society.


Lancaster University

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A digital rendering of a blood clot travelling through a vein.
Blood clots can form in the lungs, brain, heart, or veins. SciePro/Shutterstock

There’s been a lot of concern in recent days about blood clots, particularly after reports from Germany of people developing cerebral vein thrombosis – a blood clot in the brain – after receiving the Oxford/AstraZeneca vaccine. Other European countries have raised concerns about potentially increased risks of pulmonary embolisms and deep-vein thrombosis following vaccination.

However, AstraZeneca says there is currently no evidence that clots are associated with the vaccine, and the number of blood clots reported after having the vaccine is no greater than what would occur normally.

Clotting, also known as the coagulation system, is an extremely important function in the human body. Clotting helps prevent excessive blood loss both inside and outside the body when our skin, internal organs or vessels get damaged.

But though it may be a normal and essential process, if a clot becomes dislodged from where it has formed, it can become dangerous – especially if it becomes lodged in an organ, or in an artery that’s too narrow for it to fit through. This is typically known as an embolus. This can block arterial blood flow, which is essential to vital organs and may result in a pulmonary embolism (blood clot in the lungs), ischaemic stroke (clot in the brain) or a heart attack. They can also block veins, such as a deep vein thrombosis in the legs – known as a thrombus.

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Many things can increase a person’s chance of developing a blood clot. Here are five:

1. Obesity

People who are obese are more than twice as likely to develop a thrombus (blood clot in the leg) compared with people of a normal weight. This is because obesity causes chronic inflammation and reduced fibrinolysis (ability to breakdown clots).

Chronic inflammation also happens as a result of having less nitric oxide in the body. Nitric oxide is a molecule that protects the specialised endothelium (the blood vessel’s lining) and prevents cells from sticking to the endothelial surface. Even at an early age, people who are obese have significantly lower levels of nitric oxide. It’s this reduced amount of nitric oxide in obese people that increases damage to the lining of blood vessels, in turn, increasing the risk of clots forming.

2. Smoking

Smoking increases the risk of blood clots forming by up to threefold.

As with obesity, smoking reduces the amount of nitric oxide in the body and encourages the blood to stick together to form clots. This process is driven in part by significantly increased levels of fibrinogen, an important component in clotting, present in the blood of smokers. Chemicals in cigarettes also cause platelets in the blood to stick together. Together, these factors make the blood thicker, making it harder for the heart to pump it around the body, in turn, damaging the inner lining of the blood vessels.

3. Flying and inactivity

Travelling long distances in aircraft, or being immobilised for a long period after major surgery, can increase the risk of blood clots in the form of deep vein thrombosis (DVT) – blood clots in the legs. The typical incidence of DVT is one in 1,000, but it increases up to threefold on flights longer than three hours.

Person holding their leg in pain.
Sitting on a flight can increase risk of blood clots in legs. Boyloso/ Shutterstock

Because the blood is not flowing as much, the cells and proteins in blood settle out and form clumps. When the person starts moving again, these clots can move around the body and block a blood vessel if they are not broken down. Increased body mass index, age and smoking increase the risk of developing DVT from inactivity or on flights.

4. Trauma and cancer

As many as one in four people who have had major trauma, which causes damage to blood vessels – such as if large bones have been broken – develop clots. In such cases, the clot formation is linked to both the injuries to the blood vessels themselves, as well as the often prolonged bed rest associated with treatment and recovery.

Similarly, people with cancer are five to seven times more likely to develop blood clots. This is because some cancers produce increasing amounts of coagulation factors that promote clotting. Cancer also damages healthy tissues, which causes them to swell and clot.

5. Contraceptive pill

Women taking the combined oral contraceptive pill containing artificial oestrogen and progesterone have been found to have a small increased risk of blood clots. Other oral contraceptives show similar levels of increase, with about 6-17 extra events per 10,000 women treated depending on the drug used, compared with women who don’t take the oral contraceptive.

The ingredients in contraceptives increase the levels of several clotting factors circulating in the blood, which increases the odds of blood forming clots in veins.


Research also shows that COVID-19 patients have significantly elevated levels of a molecule that forms when clots are present. This is because COVID-19 attacks the endothelial cells lining blood vessels, causing an increase in clots throughout the body and presenting as a vascular disease. One study also found between 2%-9% of COVID-19 patients develop pulmonary emboli (blood clots in the lungs). And COVID-19 patients are between three to six times more likely to develop blood clots in the veins compared with the rest of the population. Other factors – such as bed rest and age – may increase the risk of blood clots in COVID-19.

But while many factors can increase a person’s risk of blood clots, there’s still no evidence to suggest a link between the AstraZeneca vaccine and blood clots.

Message from Dr Holloway

Out receptionists and telephone system is likely to be very busy this week due to inquiries about the Covid Vaccine. I will ring you if any of you have problems getting through to me for your telephone consult.