Home blood pressure – a handy how to guide

High blood pressure is the single most important risk factor for cardiovascular disease. This group of diseases, which includes heart attack and stroke, is responsible for 1 in 4 deaths worldwide and 1 in 3 deaths in Australia. Recently, the National Heart Foundation demonstrated that less than 1% of people diagnosed with high blood pressure would modify their lifestyle to reduce their risk of heart disease (1). Up to 50% of people with high blood pressure are completely unaware they are at risk.

Why is blood pressure important?

“High blood pressure doesn’t necessarily have any symptoms. Unless we measure it accurately we often don’t know if we have high blood pressure” warns Prof. James Sharman from the Menzies Institute for Medical Research.

It is critically important that blood pressure is regularly measured using a validated blood pressure device (more on that below).

What is blood pressure?

You’ve probably had your blood pressure taken during a routine check-up with your GP, or before you donate blood or plasma at the local blood bank (kudos to all you good Samaritans!). You may have noticed that the reading is one number over another number, for example, 120/80. These two numbers are measurements of the pressure of the blood moving through your arteries (tubes that carry oxygen enriched blood from the heart to your cells). The larger, top number, is the “Systolic” blood pressure – the maximum pressure your blood will reach as the blood is pumped out of the heart. The lower, bottom number, is the “Diastolic” blood pressure, which is the lowest pressure the artery will have, as the heart is refilling between beats.

So why is blood pressure so dangerous?

Generally, the pressure of our blood reduces as it travels from our heart out along our arteries to our smaller blood vessels where it is passed along to our cells via even smaller tubes called capillaries. The force of the blood being pushed through these tubes by the heart lessens as the blood gets further away from the heart and reaches its destination. When we have high blood pressure, the blood that reaches our cells can have such high forces that it damages organs including our brain, kidneys and eyes, causing rupturing of the capillaries.

Blood pressure measurement: the good, the bad and the ugly

The good:

Measuring blood pressure is extremely important to identify people at risk of problems related to high blood pressure. There are many different ways blood pressure can be measured. Doctors measure your blood pressure, either using an automated device with a cuff at your arm or manually with a pressurized cuff and a stethoscope to listen for sounds at your arm to measure blood pressure. Doctor-measured blood pressure has several limitations, including the phenomena called ‘white coat hypertension’ where the doctor records a high blood pressure reading because the patient is tense due to the situation or setting. Perhaps they’re nervous about visiting their doctor, perhaps they’re nervous about what the blood pressure reading will say, but they normally have a healthy normal blood pressure when calm. This elevated blood pressure when nervous is an evolutionary feature of the “fight or flight” response. When anxious or feeling in danger, our blood pressure increases to keep oxygen supply to the brain, and to make sure we have oxygen in our system to supply our muscles if we need to run. Think about how you might feel before a speech or presentation at work – your heart starts to race, you get flushed – what you may not be able to tell is you also have an elevated blood pressure in that moment.

Therefore, the gold standard method of measuring blood pressure is away from the doctor and using a device that measures your blood pressure automatically over 24 hours. The 24 hour method gives an indication of what your blood pressure is like when you’re undertaking your usual activities. The blood pressure numbers from the 24 hour method can be more accurately linked to risk of heart attacks and strokes than other methods of measurement. Enabling patients to measure their blood pressure at home can empower patients to have an active role in managing their cardiovascular health, and allow doctors to monitor the effect of medications.

Patients are often asked to buy a blood pressure monitor to perform at-home measurements. However, it can be quite difficult to know what type of device to buy and what the differences are. Are all blood pressure monitors created equal?

The bad:

There are rigorous international protocols developed to test the accuracy of new blood pressure monitors. If a blood pressure monitor passes this testing, it is said to be validated. However, before becoming available for sale it is not essential for new devices to undergo this validation testing. This means many monitors available on the market may not provide an accurate indication of blood pressure.

Doctor Dean Picone from the Menzies Institute for Medical Research recently investigated the types of blood pressure monitors available for purchase in Australia. He found there were almost 1000 monitors available but as few as 7% had been validated. Non-validated monitors are less likely to be accurate than validated ones (2).

“People looking to buy a blood pressure monitor are inundated with choice and are potentially more like to buy a monitor that could be inaccurate due to the high prevalence of lower cost, non-validated monitors and lack of information available on validation” says Dr. Picone

The ugly:

Now you may be thinking that even if a blood pressure monitor hasn’t been validated it’s probably better than not measuring your blood pressure at all. This is not the case. Accurate blood pressure measurement is essential to inform clinical decisions about lifelong therapy to prevent the leading cause of death worldwide. The ramifications of inaccurate measurements span from someone unnecessarily receiving lifelong medication to the flip side of someone not receiving medication when they require it, meaning they could unknowingly be left at higher risk of heart attacks and strokes.

Among the plethora of non-validated devices available, there’s the emergence of wrist-based wearables, commonly known as activity trackers, that claim to measure blood pressure. To date, the technology does not exist to accurately measure blood pressure without the inflation of a cuff and these activity trackers do not use cuff inflation to obtain the blood pressure measurement. The method of blood pressure measurement from these monitors is unclear. Essentially, activity trackers cannot be recommended for blood pressure measurement because of uncertainty about the accuracy of the readings.

Dr. Picone and Prof. Sharman demonstrated most devices available in Australia were not tested for accuracy (2)

The good news:

Prof. Sharman and Dr. Picone, alongside international colleagues who are experts in blood pressure, are working to improve international standards, ensuring the validation of blood pressure devices so that consumers can have confidence in their accuracy.

“To help consumers identify validated blood pressure monitors, we have developed this practical resource which describes all the validated device listings available globally and how to search them.”

The tool is designed for use by the general public, health professionals and policy makers to promote the uptake and use of validated blood pressure monitors and is currently being translated to several languages other than English.

What can you do?

Measuring your blood pressure at home is extremely valuable in helping your doctor make clinical decisions. Prof. Sharman and Dr. Picone have some helpful tips to make those readings as accurate and useful as possible.

How to measure your blood pressure (3)

10 easy steps to accurately measure your blood pressure at home:

  1. Use an upper arm device (not a wrist cuff or one you wear on a wristband) with a correct cuff size (within the range indicated on the cuff).
  2. Use a validated, accurate device. You can check for reliable devices here. If you don’t want to buy a device, you can hire or borrow one from some pharmacies and medical clinics.
  3. Measure your blood pressure at around the same time, morning and evening, over seven days (five day minimum).
  4. Measure before taking medication, food or exercise, and as advised by your doctor (for instance, before visiting the doctor or after a medication change).
  5. Don’t smoke or drink caffeine 30 minutes before measuring, and don’t measure if you’re uncomfortable, stressed or in pain.
  6. Avoid distractions or talking during the measurement. Sit quietly at rest.
  7. Perfect posture – both feet flat on the floor, back supported and the cuff applied directly to your bare upper arm with your arm supported at heart level.
  8. Take two measurements with one-minute rest in between.
  9. Keep a diary that records each measurement either by paper or electronically, templates can be found here.
  10. Provide your doctor with your readings, by email or via telehealth.

There are many things you can do to reduce your risk of heart disease and lower your blood pressure. We recommend you check out the Heart Foundation website for more information – they even have some heart healthy recipes.

This article was written by Niamh Chapman, Dr. Dean Picone and Prof. James Sharman from the Blood Pressure Research Group at Menzies Institute for Medical Research, University of Tasmania, with editing help from Kelsey Picard.


Professor Sharman’s Blood Pressure Research Group is working on a series of studies ranging from understanding the basic human physiology of blood pressure to exploring new methods for improving patient diagnosis and care. People have been led to believe blood pressure measurement is easy and reliable. But unfortunately in some people this simply isn’t the case. To try and address this problem we’re collaborating with cardiologists at the Royal Hobart Hospital to try and understand the factors contributing to blood pressure measurement inaccuracies.

Dr Picone is a Postdoctoral Research Fellow with the Blood Pressure Research Group at the Menzies Institute for Medical Research. His PhD studies focused on the accurate measurement of blood pressure and he is currently continuing research in this area.


(1) https://www.heartfoundation.org.au/media-releases/fatal-but-forgotten-high-blood-pressure-threat

(2) Picone DS, Deshpande RA, Schultz MG, et al. Nonvalidated Home Blood Pressure Devices Dominate the Online Marketplace in Australia: Major Implications for Cardiovascular Risk Management. Hypertension. 2020;75(6):1593‐1599. doi:10.1161/HYPERTENSIONAHA.120.14719

(3) Unger T, Borghi C, Charchar F, et al. 2020 International Society of Hypertension Global Hypertension Practice Guidelines. Hypertension. 2020;75(6):1334‐1357. doi:10.1161/HYPERTENSIONAHA.120.15026

Marvellous microbes: How to make a sourdough starter culture at home

Recently, many of us have been baking up a storm and sourdough bread has become the poster child of social isolation. However, this is not a new trend. In fact, humans have been baking bread for tens of thousands of years.

Baking bread has really taken off amidst this global pandemic, but what has caused the recent rise (no pun intended) in the popularity of sourdough? Perhaps necessity due to barren supermarket shelves or limiting unnecessary travel for food, curiosity or even boredom? Whatever the reason, when we bake sourdough we are actually performing science experiments in our kitchens.

Whether you want to give Sourdough baking a try, you’re curious about the science behind your bread, or there is room for improvement in your sourdough crafting skills, Microbiologist Dipon Sarkar from the University of Tasmania is here to tell us about the science of sourdough, the health benefits of eating it and how you can bake your own. The truth is, sourdough contains all kinds of fascinating chemistry and biology.

“Fermentation is the oldest preservation technique that we humans know. It is the way that bacteria breed. They break down glucose and other carbohydrates and produce acids in some cases and in other cases alcohol but in all cases, the energy that the bacteria use to live” Dipon explains

Baking bread harnesses the fermentation capabilities of ‘baker’s yeast’, Saccharomyces cerevisiae. Fermentation is where the yeasts or bacteria break down the carbohydrates (long sugar chains) like starch into single sugars and produce CO2 gas. These gasses (or yeast farts, as Dipon likes to call them) get trapped in the dough, forming bubbles which cause the bread to rise. Sourdough is different from regular white bread due to the “starter culture” which you add to the dough. This “culture” is a scientific term for a group of specific microscopic organisms (like bacteria and fungi) grown in a controlled way. The sourdough starter culture contains a mixture of yeasts and lactic acid bacteria (Lactobacilli) which occur naturally in the flour. The lactic acid bacteria in the culture break down the starch into simple sugars that the yeasts can use, while producing lactic and acetic acid. These acids give sourdough bread its tangy flavour and chewy texture as they modify proteins such as gluten in the flour. These acids also lower the pH of the bread which gives the bread a longer microbial shelf life, as the lower pH prevents the growth of bread mould fungi (1).

Sourdough is not a new trend.

“Sourdoughs have existed for a long long time” says Dipon

Humans have been making bread for tens of thousands of years before instant baker’s yeast was cultured and sold for baking purposes. In fact, Aboriginal Australians were some of the earliest known bakers – harvesting native seeds and grinding them into flour on grindstones to make bread. Natural yeasts on these seeds would ferment the sugars to produce bread that was then cooked over hot coals (2).

Sourdough is healthier than regular white breads, as the lactic acid bacteria are able to release important minerals in flour, such as iron, magnesium, calcium and zinc, which are otherwise bound to phytic acid in the flour (3). The bacteria’s break down of phytic acid means these minerals are available for our bodies to absorb. Thank you, good bacteria!

So, how do you create a starter culture?
You mix water and flour and leave it to ferment for about a week, though if your kitchen is particularly cold (ahem.. Tasmania..) it may take up to two weeks.

“As long as the flour is un-bleached, you can use it to make sourdough culture” advises Dipon.

Some bakers prefer to use stone ground or wholemeal flour as it often contains more of the microbes that create a good fermentation culture.
After about a week you should notice bubbles being produced from the culture – a good sign that the yeasts are alive and fermenting! The culture should double in size every 5-7 days, which is also approximately the length of time that you need to feed the culture for once it is established. Yes, because the starter is a living culture, you need to keep it alive, and like any pet, it will need food (flour), water, and love. Think of it as a modern day tomagotchi for any 90s kids reading this.

You will need:

  • Flour
  • Water (tap is fine)
  • A glass jar (around 750mL)
  • Kitchen scales

Day 1: Start your culture!

Add 100g of flour (whole wheat, or white) and 100g of water to the jar and mix with a fork. The mixture should be the consistency of thick pancake batter. You may need to add some extra water if it seems too thick.

Cover loosely and leave in a warm (~24°C) spot for 48 hrs. If you live in a cold house (and let’s be honest, we’re posting this how to blog right at the beginning of winter in Tasmania, so it is cold) you can find a warm spot perhaps on top of your fridge, in the hot water cylinder cupboard or you could set up a lamp pointed at the culture, so the light is giving off a small amount of heat. I took my culture into the office with me, so it wouldn’t sit in an unheated house all day. True love.

Day 2: Keep an eye out

You do not need to do anything today but look at your culture.
You may see some bubbles already, or you may not. Either is okay.
If you notice a black watery layer on the top of your culture at any point, do not be alarmed, this is called “hooch” and is a sign your culture needs to be fed. Hooch is the yeasts producing alcohol because they have not been fed fresh flour and have not been recently mixed leading to a low oxygen environment (this is how alcohol is made, feeding yeasts sugar to ferment in a low oxygen environment). You just need to pour off the liquid and feed the sourdough (below).

Day 3: Feeding time

By now you should see some bubbles, and the culture should have a fruity aroma, if not, feed it anyway:

Remove half the culture from the jar with a spoon and dispose of it. The culture will double in size with each feeding so you need to dispose of some.
Add 100g of flour and 100g of water and mix into the starter culture. Leave in the warm spot for 24 hrs.

Days 4, 5, 6: Repeat

Repeat the feeding process every day, removing half the culture and adding flour and water.

You will notice the culture will rise between feedings and should have bubbles throughout.

Day 7: IT’S ALIVE!

By day 7 you should notice that the culture doubles in size when left for 24 hrs. You can place a rubber band on the outside of the jar to mark the level when you feed it to see the change in size over time.

The texture should be thick and spongey with lots of bubbles and should have a pleasant smell. You can also try the “float test” by placing a spoonful of starter in a cup of water. If it floats on the surface, it is now ready to be used in your sourdough recipe!

Once your starter is properly established and has this spongey, marshmallow texture before each feeding consistently, you can begin to neglect it a little more. You can keep the culture somewhere cooler – perhaps on the kitchen bench or even in the refrigerator to really slow its growth – The lactic acid bacteria grows better in cooler temperatures, so keeping your culture cool can increase the sour flavours of the bread. This slower growth means you can feed your culture whenever you take some out to make bread, weekly works best.

Now go ahead and marvel at some microbes, get some loaves in your life and bake away the boredom! Keep us updated on your progress by tagging @ThatsScienceTas on social media.

Dipon Sarkar

Special thanks to our expert guest, Dipon Sarkar! Dipon is a PhD student at the Tasmanian Institute of Agriculture, University of Tasmania, specialising in food science and food safety.

This article was written by Kelsey Picard with thanks to Kate Johnson and Niamh Chapman for editing assistance, and to Lachlan Tegart for supplying photos.


  1. CORSETTI, A. & SETTANNI, L. 2007. Lactobacilli in sourdough fermentation. Food Research International, 40, 539-558.
  2. PASCOE, B. 2014. Dark Emu: Black Seeds: Agriculture or Accident? Magabala Books. Broome, W.A.
  3. LEENHARDT, F., LEVRAT-VERNY, M.-A., CHANLIAUD, E. & RÉMÉSY, C. 2005. Moderate Decrease of pH by Sourdough Fermentation Is Sufficient To Reduce Phytate Content of Whole Wheat Flour through Endogenous Phytase Activity. Journal of Agricultural and Food Chemistry, 53, 98-102.

Knitting, baking, and ice-breaking: Transitioning from Social distancing to everyday life

As we grapple with the changes that social distancing and self-isolation have brought to our lives, our experiences begin to align with those of NASA astronauts and Antarctic scientists who live and work in isolation. As we bake, knit, read and contemplate what life will be like when the threat of coronavirus has subsided, our brains are changing.

Associate Professor Kimberley Norris from the University of Tasmania is a clinical psychologist who studies how people respond to extreme and unusual situations like isolation. Kim’s research into how people cope in environments such as Antarctica and Outer Space can provide insights into how our minds are changed by periods with minimal social interaction.

It’s a rollercoaster

Isolation for very short periods of time (less than a few weeks) results in small, and often temporary, mental changes as we essentially give ourselves permission to ‘ride it out’ without making major adjustments. Once isolation has continued beyond a few weeks we start to see some changes in people’s psychology, how we emotionally respond to situations or how resilient we could be to change.

People experience similar patterns of mood fluctuations when isolated for longer periods. Initial excitement subsides causing our mood to stabilise or ‘plateau’, followed by declines in mood and wellbeing. After several weeks, challenges become harder to navigate as we feel like we’ve been dealing with isolation for so long but have to keep going. This is especially difficult when there is no clear end in sight, or if the end date keeps changing. Generally, humans are creatures of community and habit. People like having control and predictability in their lives, it provides comfort and the ability to plan and of course much needed time for fun and leisure!

Kim highlights that “alongside the rollercoaster of emotions brought on by isolation, we can struggle to think, concentrate and remember as well as we would in ‘normal’ circumstances”. This is due to an increase in the number of thoughts our brains have to process (known as “cognitive load”). These thoughts include responding to our new routine and our changed environment. Each day we are receiving more information about the pandemic or adjusting to updated restrictions – that’s a lot to mentally process! As a result, our attention, concentration, memory and problem-solving abilities decrease. This is often temporary and returns to normal within a few months post isolation.

Men and Women may respond differently

Following periods of prolonged isolation, we see changes in the way that men and women respond and engage with the world around them.

“People who identify as male are generally quite independent, strong in their beliefs to cope with most things and they tend to be quite self-sufficient, they keep their challenges to themselves” Kim says.

However, during isolation when your survival can depend on the people around you, males reach out to their immediate network or community for support to work through the challenges of isolation. Men expanding their social networks and reaching out for support during isolation may have many positive mental health benefits that last well beyond isolation. According to Kim, “generally speaking, males who have been in isolation will come back with much stronger social networks and a better ability to reach out to other for help when they need it”

In contrast, women stereotypically already use social support to a much greater extent than men as part of routine life. Kim says,

“They (Women), instead become much more confident in their own abilities”

So, in isolation, many women may be relying more on their own skills and therefore working more independently. As a result of the greater self-confidence and trust in their abilities, women have been shown to be more likely to pursue career changes and opportunities for advancement after periods of isolation.

However, this is a simplification and of course it is often much more complex than this. For example, recent research has shown that the increased caring load during the Covid-19 crisis is bourne largely by women and that women make up 70% of the healthcare workforce (1,2). An increased domestic and caring load and the high proportion of women in healthcare professions may mean that the traditionally cited benefits of isolation may not be felt by many women.

Whether or not we are isolated by choice influences how we cope

There are many situations where people choose to be isolated (known as self-selection), for example people working on remote islands manning lighthouses, in space or in Antarctica. In these situations, people typically receive training to prepare for isolation, which equips them with skills to adjust to isolation. Kim says that this preparation “facilitates better adaptation as it allows the world to feel more predictable, enabling us to feel more in control, and less anxious”.

In contrast, when isolation is thrust upon us, such as isolation due to the COVID-19 pandemic, we have not had a choice to isolate, time to prepare or access to specialist training. The environment and available information are also rapidly changing, so the world can seem much less predictable than before. As we were unable to prepare for isolation, a lot more mental energy is needed to navigate the changing world around us. While this doesn’t mean that we can’t do well without preparation, it makes it a more challenging journey.

As coronavirus restrictions start to ease and we start to return to work and re-enter public spaces, what can we expect?

Every day life will be different

“Life will not simply pick up where we left off. Too much has changed – we have changed as individuals, as well as a society.” Kim says.

We’ve developed new routines and expectations, and we need to create a new normal. Several factors are likely to contribute to nerves about restrictions relaxing and people will vary in how they respond. Generally, people will be fearful of the ongoing risk of transmission of COVID-19, apprehensive about resuming work or sending the kids back to school, and nervous about mixing in large groups again as we’re out of practice! We’re also likely to experience sensory overload as more people are out in public and activities resume – we’ll be exposed to more and louder noise, smells and sights. However, when we establish our new normal, our anxieties will be eased and we will find ourselves developing new habits that help us to navigate our world.

You may be excited for the return to a life with social gatherings and international travel, or you may be apprehensive about re-entering a changed world, having enjoyed the benefits of social distancing.

Whether you’re excited, anxious or a little bit of both, Kim has some tips to ease your transition from self-isolation and social distancing back to everyday life.

Three easy steps

  1. Protect the good things that isolation has given you
    There may be some things about isolation that you like – reduced time pressures, a new hobby, more time with the kids, or improved balance between different aspects of your life. Part of successful adaptation and ‘thriving’ post isolation is making time to continue doing things you enjoyed during isolation. Not only will this help you to find a sense of meaning and purpose in your isolation experience, but more importantly, these type of self-care activities decrease the impacts of sensory and mental overload and help you adapt more effectively.  
  2. Make it a staged transition
    Just because you can do things again, doesn’t mean you have to, and doesn’t mean you have to do it all at once. Give yourself permission to take your time to make the transition – known as ‘systematic desensitisation’, or ‘graded exposure’. Some days you will feel up to the challenge, other days not so much. Be kind to yourself. Be patient. Listen to what your mind and body are telling you. Create opportunities to do things, but without high levels of pressure.
  3. For Now
    Physical distancing combined with social connection leads to good mental health. Stay connected with your family, friends and colleagues via one of the many platforms we have available to us like zoom, skype and phone calls. Don’t wait for it to all be over, take up hobbies, focus on activities which give you a sense of achievement. Choose small tasks remembering to be gentle with your brain, which is working overtime.

Unlike the elite researchers that Kim has worked with, our isolation has been thrust upon us. It’s understandable that we may be feeling anxious. Be kind to yourself and remember that like explorers of Antarctica and space we’re navigating unchartered territory, in our kitchens, homes and brains.

If you or someone you know is struggling please call life line on 13 11 14 or access the websites below for helpful information and resources:

Headspace: http://www.headspace.org.au

Beyond Blue: http://www.beyondblue.org.au

Reach Out: reachout.com

This article was written by Kate Johnson, Niamh Chapman and expert guest Associate Professor Kimberley Norris.

Kimberley Norris is a psychological scientist and clinical psychologist who works across academic, research, and clinical psychology practice settings. She is an Associate Professor in the School of Psychological Sciences at the University of Tasmania. Her overarching research and academic interests are focused on adaptation and resilience, and maximising human health, wellbeing and performance in both normal (e.g. academic) and extreme environments (e.g. Antarctica, space, FIFO).


(1) Workplace gender equality Agency (2020) Gendered impact of Covid-19, viewed 30 May  2020, available: https://www.wgea.gov.au/topics/gendered-impact-of-covid-19.

(2) Boniol, M, McIsaac, M, Xu, L, Wuliji, T, Diallo, K & Campbell, J (2019), Gender equity in the health workforce: Analysis of 104 countries, World Health Organisation, viewed 30 May 2020, available: https://www.who.int/hrh/resources/gender_equity-health_workforce_analysis/en/.

Image 1: Aurora Australis and Image 3: In The Ice, credit : Kimberley Norris