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Article Analysis: Pandemic Blood Pressure Increase

Article Analysis: Pandemic Blood Pressure Increase
Photo Credit: OurTIme

Article Link: National Heart, Lung, and Blood Institute

Hypertension, or high blood pressure, is a major health concern for the United States, with a diagnosis level of nearly 50% among Americans aged 20 and over in 2018.[1] The represents an increase of nearly 20% from the late 1980s (41.4% in 1988 to 49.6% in 2018)[1], and has led to an increased burden on medical professionals, who reported 33.6 million physician visits in 2018 that cited hypertension as the primary concern.[2]

Hypertension is classified as abnormally elevated pressure in a person's arteries and is detected using a blood pressure cuff. Anyone who has been to a doctor's office is familiar with the saying "your blood pressure is X over Y," with x representing the systolic blood pressure and y the diastolic. Systolic blood pressure is the pressure created by the heart as it beats, and can be thought of as the amount of work needed to circulate blood through the entire body. If arteries are clogged or scarred, it takes more effort to pump blood and thus results in a higher systolic number. Diastolic, by contrast, is the pressure in the blood vessels when the heart is between beats, or at rest. Combined these number provide a good indicator of overall circulatory system health. Though there is some debate, the high end cutoff for normal blood pressure values is typically 120/80 for adults.

Beyond scarred or clogged arteries, other factors impact heart health that can contribute to elevated blood pressure levels. These are typically divided into two different categories:
- Intrinsic: Age, Family History, Gender, Ethnicity [3]
- Modifiable: Exercise Level, Obesity, Sleep Apnea, Smoking, Excessive Drinking, Diabetes, High Cholesterol, and Stress [3]

Stress is the culprit we will discuss in this week's article review. The article, Rise in Blood Pressure Observed Among US Adults During the COVID-19 Pandemic, by Laffin et al. tracks trends in blood pressure for patients from 2018-2020. Their findings indicate a correlation between rising baseline blood pressure levels in US adults as a response to the COVID-19 pandemic and subsequent lockdowns.

Everyone has stressors on their body that can stem from any aspect of their lives, work, family, mental health, etc. and it is the response to these stressors that dictate how much they may impact one's overall health. At its most basic, one can think of stress as the toll taken on a person by the physical and mental tasks and loads they undertake. When these loads are too great or the individual is not equipped to deal with them effectively, they can negatively impact health.

In addition to the stressors many of us immediately think of, work, children, relationships, there is a baseline level of stress that exists in the world. This baseline stress can be influenced by the overall well-being of a society and its citizenry. It is obvious that this baseline has elevated over the last two years due to the COVID-19 pandemic and a charged political climate. Did this elevated background stress increase blood pressure in Americans as would be expected?

Study Methods:
Laffin et al. utilized data collected from nearly 600,000 individuals through an employer sponsored wellness program offered by Quest Diagnostics. Little information is provided about this program, however it is likely an opt-in program where employees are rewarded for providing health data under the guise of helping monitor and improve health outcomes.

Using these data points, the researchers created a longitudinal study where they compared blood pressure data from 2018 to 2019 and two time periods in 2020 (Jan-Mar and Apr-Dec). These timeframes were chosen as most locations began to experience high case volumes and local restrictions due to COVID-19 in late March/early April of 2020.

NOTE: A longitudinal study is one where researchers measure the same participants over a period of time and compare the results. In this case, patients were only included in the study if they had valid blood pressure readings from all three calendar years.

Participant Data:
The final number of participants in the study was 464,585, a group that was 53.5% women with a mean age of 45.7 and standard deviation of 11.1 years. It is likely that the combination of group cohort size and standard deviation values indicate this is a good sampling for the study. There could still be bias introduced however, as there is no indication of race, smoking, or other factors that could sway the numbers. For example, people willing to include themselves in work-sponsored health reporting may be less likely to be smokers and thus could impact the data differently.

Overall, I would be content with using this data for this purpose because of the size of the data set and the overall simplicity of the data involved. There is no qualitatively measured component in blood pressure. That said, if we were to create this study in a perfect world we would control for blood pressure cuff type, time of data collection, and prevent self-reporting.

NOTE: Standard deviation is a measure of how much statistical variability there is in a group. The standard deviation for a classroom of kindergarteners would be low as all the students are around 5 years old. A standard deviation of 11.1 years indicates a wide variety of ages in the patient groups.

Example of Normal Distribution of Ages in the Data Set

The above graph is a quick representation of the normal distribution of a dataset with the qualities present here (mean = 45.7, sd = 11.1, size = 464,585). While there is no indication that the data is truly a normal distribution, this is an effective way of understanding how the dataset appears at a glance.

Blood pressure values did not appear to change between 2018 and 2019 or from Jan-Mar 2020 to 2018/2019. The researchers did find a statistically significant increase in both systolic (between 1.10mm Hg and 2.50mm Hg on average) and diastolic pressure (between 0.14mm Hg and 0.53mm Hg on average) for readings taken between April and December of 2020. This appears to indicate that exposure to the pandemic and its ramifications has led to increased blood pressure in US adults. (All p<0.0001)

NOTE: A probability value or p-value is a statistical representation of how likely an event or observation is to be random. A higher p-value indicates a greater chance that a result is random and scientists typically use a p-value of 0.05 as the cutoff point for significant results. This means that there is just a 5% chance the observed events or results can be attributed to random chance. For this study, a p-value of <0.0001 means there is a 0.01% chance the increases in blood pressure are attributable to random chance.

The researchers also then categorized individuals based on American BP Guidelines (categories = normal, elevated, stage 1 hypertension, stage 2 hypertension) and compared these designations over time. They found that a greater portion of patients were categorized in the next higher category (normal to elevated, elevated to stage 1) during the pandemic months of Apr-Dec 2020 when compared to previous years.

The only other metric they looked at, based on the data provided was weight. The researchers found no evidence for weight gain during the pandemic and thus ruled it out as a cause of the blood pressure change.

Blood Pressure Change Comparisons (Systolic and Diastolic)

Looking at this first half of their visualization, we can see the variation observed from 2019 to 2018 (blue line) and the variation observed from 2020 to 2019 (red line). Right around March 2020, blood pressure values began to climb over their previous year counterpoints, however this visualization makes the systolic increases appear much more dramatic than the diastolic. If I was creating this image, I would have normalized the values to a percentage over the baseline (for example 2.5mm Hg systolic is a 2% increase, while 0.5mm Hg diastolic is 0.6% increase). I don't think these images capture those values very well.

Visualization Continued

I like the second half of this image even less than the first. I feel as though the way the chart is created is manipulative, indicating the changes in blood pressure are more impactful than they may actually be. Below are two quick mockups I did using the provided data for the male, age 65-88 years group. As you can see, stacking the increase on top of the previous baseline systolic blood pressure values (set to 120 since no average was reported in the study) changes the perception of the increase. The second has the x-axis adjusted to the normal values for systolic blood pressure (90-120mm Hg). We can see here that increase is still present but appears much less damning. How data is reported in visualizations can have an even bigger impact than what data is reported.

The researchers conclude that blood pressure has risen during the pandemic months of April to December 2020 and have identified the COVID-19 pandemic and associated restrictions as a cause. I think this is oversimplified, as the 2020 US Presidential Election was also highly stressful during this time and should be included in the stressors that affected American's health in 2020. I would be willing to acknowledge that the overall blood pressure of Americans appears to hav elevated in 2020 and COVID-19 is a contributor. Additionally, if the patients are having their blood pressure taken in a doctor's office, it could be indicative of less an increase in baseline blood pressure and more an increased apprehension about being out in public.

I also don't want my comments on the presentation of the data to bely the importance of their findings. As the researchers mentions, a small increase in the population blood pressure (even just 2mm Hg on average) can be indicative of increased heart attack, stroke, or heart related illnesses in the coming months/years. This is a serious issue and shows just how much the background stressors in society can impact the overall health of the population.

[1] - https://www.cdc.gov/nchs/data/hus/2019/021-508.pdf
[2] - https://www.cdc.gov/nchs/data/ahcd/namcs_summary/2018-namcs-web-tables-508.pdf
[3] - https://www.heart.org/en/health-topics/high-blood-pressure/why-high-blood-pressure-is-a-silent-killer/know-your-risk-factors-for-high-blood-pressure