Many of the health changes associated with urbanization are thought to be a direct result from reductions in physical activity levels. As physical activity is well documented to be protective against many ailments, such as cardiovascular disease, type 2 diabetes, and some types of cancer, urbanization has the potential to negatively impact human health.  A recent study has indicated that the urbanization additionally may have widespread effects on the joints of its citizens.

In a study from Nicholas Holowka and Ian Wallace, Harvard University, the University of Buffalo, and the University of New Mexico, knee cartilage thickness was examined via ultrasonography in children living in both urban and rural Kenya. Western Kenya is an ideal location to study the effects of urbanization as many small communities still practice small-scale farming while being closely located to the more populated city of Eldoret. Children from ages 8 to 17 were recruited in order to see how knee cartilage thickness changed throughout childhood.

As loss of knee cartilage thickness is a risk factor for the development of osteoarthritis, this study aimed to uncover any differences in risk for developing knee osteoarthritis later in life due to urbanization. Interestingly, despite the study focusing only on osteoarthritis, a disease often associated with old age, the rate of reduction in knee cartilage thickness was still significantly less in the rural children compared to the children living in an urban environment. For the urban participants, knee cartilage thickness declined an average of .11mm per year during childhood. However, the rural children only saw knee cartilage thickness reduced an average of .047 mm per year. These results suggest that urbanization results in a greater risk for knee osteoarthritis, which can be seen even within childhood. So what is causing this increased risk in urbanized children?

One hypothesis that has been suggested is that the increased risk of knee osteoarthritis for those living in urban environments is due to dietary changes and increased fat accumulation. This theory holds that the dietary changes of urbanization promotes low-grade inflammation from the release of adipokines from excess adipose tissue. Adipokines, such as leptin, are cell signaling proteins that are secreted from fat tissue and can promote inflammation throughout the body. However, as mentioned previously, there were no differences between rural and urban children in terms of BMI in the current experiment and yet, knee cartilage thickness was still reduced in children living in urban areas. This would be unlikely if obesity-derived low-grade inflammation was the main culprit for loss of knee cartilage.

A similar study as the current investigation conducted within an urbanized country may help provide more insight. This study revealed that there was an association with low levels of physical activity and decrements in knee cartilage thickness within children.  Animal studies  also confirm that  decreased physical activity through unloading promotes  a loss of cartilage, potentially due to  metabolic changes in chondrocytes. In the current study, children who were overweight did not show a correlation in a reduction in knee cartilage thickness. Taken together, these results suggest that physical activity levels, but not obesity, are likely responsible for the decrements in knee cartilage thickness seen within urbanized environments.

For those living in an urbanized country with a market-based economy, these results are potentially troubling. The health consequences of urbanization likely extends far beyond just obesity, as seen by the current study. And these changes and risk factors are already present within children living in urbanized environments. Additionally, this study challenges one of the commonly held paradigms of what constitutes healthy living. So often the numbers on the scale are considered the gold standard measurement that reflect overall health and wellness. However, physical activity levels, regardless of fitness levels and BMI, may play an important role as well.

Indeed, osteoarthritis rates are very prevalent within the United States, especially within the aging population. As many as 10-13% of Americans over 60 will be diagnosed with osteoarthritis. As living within an urbanized environment has been shown to be correlated with reductions in physical activity levels, this may not come as a big surprise. However, research such as the current study is vital in providing a clear understanding of the health issues deriving from urbanization. As the topic is increasingly investigated and the wide-spread effects of urbanization on human health is understood more thoroughly, hopefully these challenges can be met with better preventative health measures.

Many of the current risk prediction algorithms place the most emphasis on age as a contributor in developing CVD. Consequently, CVD risks for many younger adults are often underestimated. A recent study from vascular physiopathologists in Spain searched for a new method to estimate CVD risk for this population using a technique called proteomics, by quantifying risk of CVD in young adults based on the proteins found in their plasma. They were particularly interested in oxidative stress markers, because oxidative stress is associated with the development of CVD. Oxidative stress occurs when you have more free radicals than antioxidants in your body, which damages your cells.

The study placed younger adults into three groups: healthy participants, participants with risk factors for CVD, and those who had already experienced a cardiovascular event. Among the proteins found in the participants' plasma samples, the team identified more irreversible oxidation of certain amino acids in those who had experienced a cardiovascular event, compared to healthy adults. 

The results indicate that oxidation is progressive with the development of CVD. Additionally, there were increases in the antioxidant response for both the adults with CVD risk factors and patients who had already experienced a cardiovascular event. This antioxidant boost is assumed to be a response to the increased oxidative stress seen with CVD.

Ultimately, these results revealed exciting findings that both markers of oxidative stress and the antioxidant response are altered in those at risk for CVD. Thus, these biomarkers may be clinically useful in developing better tests to quantify the risk of CVD in young adults.

However, what happens when one of these companies publicly claims to be able to predict the risk of infection from a disease?

WHOOP is a wearable fitness technology company that has received media interest for claims of being able to predict risk of COVID-19 earlier than the onset of noticeable symptoms. They claim that monitoring the user’s resting respiration rate (taken when the user's breathing rate is the lowest, at night) can help in early detection of the virus. COVID-19 is, first and foremost, a respiratory tract infection that can cause respiratory distress. If the WHOOP app notices any abnormal variation in the user’s resting breathing rate, wearers may receive a notice that they are at risk of being infected by COVID-19. By being able to identify any abnormality in respiration, users could potentially get tested and isolate themselves earlier than they would otherwise.

The company, which has financial backing from the co-founder of Twitter Jack Dorsey and NBA basketball player Kevin Durant, received even further attention when pro-golfer Nick Watney was alerted, accurately, via the WHOOP app that he may have COVID-19. This led to the PGA tour acquiring WHOOP straps for its employees and athletes. But besides anecdotal accounts, what is the scientific evidence that this fitness strap can accurately predict COVID-19 infection from respiration rate?

Only one study exists examining WHOOP’s claims regarding COVID and, despite media outlets reporting this paper as scientific evidence of the validity of the device, it has yet to be peer-reviewed. Incidentally, this study was funded by WHOOP, and was also a collaborative effort with researchers from Central Queensland University and WHOOP. Laying aside the bias of being conducted and funded by WHOOP, this study, at least on the surface, seems to have positive results. WHOOP's algorithm to track respiration rate was able to identify 20 percent of COVID-19 positive individuals two days before those users started reporting symptoms, and 80 percent of positive cases by day three of reported symptoms. Identifying a COVID-19 infection this early would allow patients to get tested and isolate themselves much earlier, potentially slowing the spread of the disease.

Unfortunately, the positive results seem less impressive when diving into the study's methods. WHOOP was tasked with creating an algorithm that could monitor nightly variation of respiration rate and identify abnormal readings as a possible COVID-19 infection. However, no long-term investigations studying nightly variation in respiratory rate have been conducted. The investigators’ solution was to use their own user’s data in order to create a baseline for normal nightly respiratory variation. This supplementary dataset used 25,000 users' nightly data, accounting for 750,000 nights of sleep. By doing so, WHOOP's study works under the assumption that their device is fully accurate in its ability to measure respiration rate.

Since these devices were originally intended for promoting positive behavioral changes such as increased physical activity and improved quality of sleep, precise accuracy (as required in clinical medicine) was not necessary. Currently, only one peer-reviewed paper validating the WHOOP strap’s accuracy in measuring respiration rate at night exists. The results were  positive and conclude that WHOOP is accurate compared to the gold standard, inductance plethysmography, which measures the movement of the chest and abdominal wall to calculate respiratory rate. However, the number of participants in this study was low, and the researchers only used one night of sleep to evaluate the strap’s accuracy. A larger, more extensive clinical study would likely be required to validate the accuracy of the WHOOP strap.

Potential problems also exist in the inclusion criteria for subjects. For this investigation, all subjects were already WHOOP customers and either had already begun self-reporting COVID-19 symptoms or had been tested for COVID-19 infection. This choice in inclusion criteria represents a methodological problem as the population used in this study may not be representative of the general population as a whole. Using only WHOOP users could affect the sensitivity of the algorithm as the demographics may not accurately reflect the general populace. And by only including subjects that were already self-reporting COVID-19 symptoms or had already undergone testing, subjects experienced a much higher rate of infection than the general population.  Although the algorithm identified many of the COVID-19 positive cases in their investigation, its ability to predict infection in much larger populations with lower rates of infection, as well as ailments with similar symptoms, remains untested.

Indeed, monitoring respiration rate in a population that likely has been exposed to COVID-19 may in fact be a potential tool for early detection. However, variation of respiratory rate is also a common symptom for many ailments such as mild infections. Unfortunately, WHOOP’s algorithm shows no ability to discriminate between a possible COVID-19 infection from any other pathological condition that features a variation in respiration, likely limiting any potentially useful application.

WHOOP's studies leave many unanswered questions regarding their strap's relative accuracy, as well as ability to predict risk of COVID-19 infection in a clinically useful way. And yet it is entirely possible that the fitness band does everything that it is purported to do. However, when a brand or company takes a step into the realm of clinical medicine — by claiming ability to predict risk of infection from disease, for instance — such claims need to be rigorously investigated.

Unfortunately for WHOOP, there is a lack of empirical evidence that would likely prevent this type of technology from being widely used in the fight against the spread of COVID-19 infection. WHOOP represents a useful reminder to maintain a healthy skepticism when dealing with claims from a company, especially in regards to the health and wellbeing of the consumer.