Don’t track your sleep, but do track your daylight exposure
Just because we can get data on almost everything from rest to gut health, it doesn’t mean we should. We ask the experts what is worth monitoring.
Counting steps and plotting sleep were once the main attraction of a fitness tracker. But the latest devices will tell you so much more than how hungry, tired or inactive you are, providing data about irregular heart rhythms, menstrual cycles, gut health and the hours we spend in natural daylight. There is no limit to what we can track with smartwatches and apps, but do we really need to keep such close tabs on every aspect of our health?
Trackers can be “powerful and informative tools” but just because we can track almost everything it doesn’t mean we should, a review published in the International Journal of Environmental Research and Public Health found. Researchers from Daemen University in New York and the University of Ottawa looked at the pros and cons of health trackers and concluded that while they can be useful, the information they provide can be misleading and inaccurate. “Technology is continuously improving,” Jennifer Scheid, an associate professor of physical therapy at Daemen University and lead author of the paper, says. “But there is a lot of variation in the reliability and validity of different devices and the different components of health that they measure.”
Sleep tracking is notorious in creating unhealthy obsessions with poor sleep quality in those who already struggle with insomnia. As one sleep scientist told me, you don’t need a tracker if you regularly get seven to nine hours a night because you know you are well rested, so it tends to be poor sleepers who fixate on the figures they provide. Scheid’s team are planning a study on the impact of sleep tracking and her team highlighted the association of obsessive diet and activity tracking with the development of disordered eating and exercise addiction in vulnerable people.
Dr Nicola Guess, an academic dietitian and researcher at the University of Oxford’s Nuffield department of primary care and health sciences, says that some of the latest data we are becoming fixated with is meaningless anyway. “Patients I see are becoming increasingly anxious and are worrying about things they don’t need to worry about at all,” Guess says. “I see people getting worked up about what their blood glucose, for example, is doing at 2am or 3pm without any clear evidence that the data is helpful to them, and I can’t see that producing a beneficial clinical or mental health outcome.”
Your best bet, Scheid says, is to use information from trackers as a “guide to help monitor positive behaviour change” without becoming over-reliant on the results. “Taking one to two days off tracking per week may be a good idea for some people,” she says. “If not meeting a daily goal set by a watch or app creates anxiety, then that may be a sign that perhaps some time off is needed from using the device or requires the re-evaluation of how the device can be a helpful not hindering health practice.” But beyond steps, heart rate and exercise minutes, is there anything from the new array of data that is worth logging? We ask the experts.
Blood sugar
Why you might want to:
Continuous glucose monitors (CGM) were developed as a medical aid to track the blood sugar of people with diabetes but are now being used by anyone wanting to pay a premium for real-time feedback on blood sugar responses to food, exercise, stress and sleep. A small sensor attached underneath the skin of the upper arm (or stomach) measures how much sugar is in the fluid surrounding your cells every few minutes with data sent to an app on your phone. It’s not cheap. The sensors need replacing after 7-14 days (if they don’t fall off before that as they did when I tried them) and cost upwards of pounds 50 each, although you need to subscribe to a plan to get the full track service. A bright yellow CGM comes as part of the Zoe Nutrition introductory test package (pounds 299.99, zoe.com) and on top of that is the pounds 24.99 a month membership fee. When you first sign up for Levels, another company offering CGM, the cost is pounds 334, which includes the first month of monitors at pounds 129 and the annual membership fee of pounds 205. CGM should be available through the NHS to anyone with type 1 diabetes for whom the measurements are essential.
Worth doing?
Claims are that by better understanding your blood sugar responses you will learn which foods help to maintain an even keel of energy levels and wave goodbye to bad eating habits and extra pounds. “With diabetes your blood sugar does get to a level where it can cause harm and it is essential to track it so that you can adjust insulin doses,” Guess says. “And CGM can be useful for elite athletes planning their energy requirements around performance.” But she says there is no evidence that tracking blood glucose peaks and troughs is beneficial for most people, and that the pancreas does a great job of regulating the release of sugar in the body to keep it within normal levels. “The idea that people are paying a lot of money to track something that is very likely not causing them any harm worries me a lot and I can’t see any good coming from this trend,” she says. “There’s no evidence that anyone with normal glucose tolerance, that is people who do not have diabetes, need to be concerned about glucose spikes after food or a meal, which are totally normal as long as they come back down again.”
Daylight
Why you might want to:
We all know exposure to natural daylight boosts the body’s production of vitamin D, but there are other proven health benefits to getting outside. It is known to lift the mood through the release of serotonin, a mood-boosting chemical, in the brain, with Harvard researchers showing it has a powerful effect on emotional and physical wellbeing. A review of 13 studies involving 15,081 children in the Journal of Environmental Research and Public Health showed that 120 minutes of daylight exposure helps to prevent myopia (short-sightedness) and improve healthy vision. Last year a study in PLOS Biology by Timothy Brown, a professor at the environmental research institute at the University of Manchester, and his colleagues outlined the benefits of daylight exposure for synchronising the body’s internal clock. “That also helps to control function and timing of multiple biological processes that are crucial for our wellbeing,” Brown says. Light outside is often 10 to 100 times brighter than indoors, even on a dull day, and now you can track exposure to it with the Time in Daylight feature on Apple Watch series six or later. It uses the device’s ambient light sensor, GPS and motion sensors to detect how much time you spend outside, with Apple recommending a minimum of 20 minutes of daylight exposure each day for adults.
Worth doing?
Many of us don’t spend enough time outdoors to benefit our health and if this prompts you to get up from your desk or sofa more often, it can only be a good thing. Be aware that heavy cloud, shade from trees and buildings, and even a long-sleeve jacket that covers the watch and sensors might affect results, so it’s only a rough guide.
Menstrual cycle
Why you might want to:
Dozens of apps, such as the popular Flo Period and Ovulation Tracker and Clue Period, promise to track a woman’s menstrual cycle and help with everything from planning conception to monitoring pregnancy. Some, such as FitrWoman, NikeSync and CycleMapping, claim to help women sync their workouts and exercise recovery with the hormonal phases of their monthly cycle for better results.
Worth doing?
In a review of nearly 300 studies of 73 different apps, researchers reporting in the journal Human Fertility found that of the 73 per cent of fertility apps offering ovulation predictions, just over 20 per cent were accurate, with the researchers noting “severe limitations when it comes to recording menstrual cycle variability and accurate fertility prediction”. A study by Kirsty Elliott-Sale, a professor of female endocrinology and exercise physiology at Manchester Metropolitan University, found no evidence that adapting workouts to menstrual cycles using an app makes any difference. “A lot of these cycle-tracking apps are not based on sound scientific evidence and don’t track things you don’t tell them,” Elliott-Sale says. “They often base their advice purely on the dates of your period and no hormones or blood levels are involved, so the data means nothing.”
Gut health
Why you might want to:
If you don’t know by now that your microbiome, the vast community of microorganisms including fungi, bacteria and viruses that exist in the gut, plays an important role in wellbeing, where have you been? Researchers have identified “good” and “bad” bacteria that help or hinder our health, and an imbalance of gut bacteria has been associated with a range of digestion, skin and stomach issues, tiredness, weight gain and mood swings. Some apps, such as mySymptoms and Bowelle, offer advice based on symptoms and food intake data provided by the user; others, such as Zoe and Atlas (atlasbiomed.co.uk), offer personalised advice based on results of stool samples submitted and tested in a lab for results of your gut bacteria.
Worth doing?
According to the digestive disease charity Guts UK, you cannot determine “how healthy your gut is from the bacteria found in your poo”. Usually, one faecal sample is taken and the charity says that bacteria from the same person can be different one day to the next. Even if levels of different types of bacteria associated with some diseases show up, they do not necessarily indicate you are at a higher risk of getting that disease. And while the gut microbiome undoubtedly acts like an important organ in the body, Guess says we don’t yet know if tiny modifications to this complex ecosystem of bacteria through diet achieve anything meaningful. “There is no standard microbiome composition to compare against,” she says. “We don’t know the cause and effect of good and bad bugs on weight and health and much less do we know about whether modifying the gut microbiome is going to have any effect on someone’s weight or predisposition to a condition like type 2 diabetes.” Results of a study Guess is preparing to publish provide another blow to gut tracking. “There’s no evidence at all that personalising your diet according to your microbiome does anything to improve blood sugar control,” she says. “In fact we are not yet at the stage to prescribe any specific interventions that will cause long-term changes to gut bacteria composition.”
Heart arrhythmia
Why you might want to:
Fitbits and Apple Watches track irregular heart rhythms. Atrial fibrillation (AF) occurs when electrical impulses that trigger muscle contractions of the heart misfire chaotically. It affects more than 40 million people worldwide and at least 1.5 million people have been diagnosed with the condition in the UK but in about one third of patients there are no symptoms. Left undiagnosed or untreated, it raises the risk for stroke and heart failure.
Worth doing?
“The only part of any fitness tracker that has been approved as a medical device in some watches, for example the Apple Watch series four or later, is the photoplethysmography technology that is used to screen for AF,” Scheid says. However, AF is not the only irregular heart rhythm that exists – others include atrial flutter, ventricular tachycardia, ventricular fibrillation – yet it is the only arrhythmia for which existing technology monitors. Even accurate devices do not continuously monitor for AF and measurements are taken intermittently, which means it could still be missed. “Overall, though, the consensus is that a tracker might detect AF in someone who is otherwise unaware of it and is therefore worthwhile,” Scheid says.
