A new study published on the preprint server medRxiv* in August 2020 shows that heart rate variability assessments, used to evaluate the health of the heart and blood vessels, are useful in identifying changes in health and well being throughout lockdown related to COVID-19.
Lockdown and Loss of Physical Activity
As the COVID-19 pandemic spread in France, a lockdown was declared, and it stayed in place for eight weeks, from March 17 to May 11, 2020. While instituted as a necessary and lifesaving measure, its fallout cannot be ignored. For instance, it led to restrictions on outdoors and group activity, which probably reduced the general tendency to physical activity.
Indeed, a survey by a French public health institute showed that almost half the population said their physical exercise had been reduced, and about 60% of them said they walked less. On average, over 7 hours were spent just sitting, for over a third of the population. Only less than a fifth reported increased activity during this period.
Study: Effects of COVID-19 lockdown on heart rate variability. Image Credit: TheVisualsYouNeed / Shutterstock
Exercise and Mental Health
Exercise is essential for heart health and psychological well being too. One of the commonly used methods to assess cardiovascular health in athletes is heart rate variability (HRV). This is used to identify how well the sympathetic and parasympathetic nervous systems are coordinating in modulating cardiovascular tone.
Parameters of HRV
Some of the parameters include a low-frequency (LF) band, which shows both these influences but mostly sympathetic, originating from the normal vascular tone and the central regulation of sympathetic tone. The latter changes with arterial blood pressure and baroreflexes.
The high-frequency (HF) band reflects parasympathetic influence, mostly via respiration-linked changes in the sinus rhythm; the normal heartbeat changes with breathing. The parasympathetic tone goes up with exercise.
When either of these branches is not functioning correctly, hypotonia occurs and reflects poor cardiovascular condition. Such HRV assessments have been shown to be useful in evaluating stress, recovery, and well-being. The current study was meant to report, for the first time, the changes in HRV and their relationship with psychological states from the time the lockdown began. They set out to test their idea that parasympathetic- and sympathetic-related parameters would show a decline and increase, respectively, in line with negative and positive feelings of well being over the lockdown period.
The Study Participants
The study included 95 patients who had HRV monitoring devices fitted before the lockdown began. All were 18 to 60 years old and were non-smokers, healthy, active adults. All had taken at least 40 tests from January 1, 2020 to May 31, 2020, with 10 or more tests before, during or after the lockdown. This provided, say the investigators, “a unique opportunity to describe the HRV behavior in 95 healthy people.” The only limitation is that the physical activity of the participants could not be ascertained.
Most of the participants were men, with a median age of 37 years. About 20% reported increased well-being on the Visual Analog Scale (VAS). The rest reported no change or deterioration.
The decreased well-being group (80%) showed reduced parasympathetic activity, with a raised heart rate but a reduced root mean square of the successive differences (RMSSD) another measure. LF and HF also increased, in the recovery period, relative to both before and during the lockdown. This is attributed to the numerous changes leading to cardiovascular detraining. This reduces the extent of parasympathetic tone.
Implications and Future Actions
The relationship between isolation, physical activity, and reduced well-being is established. The lockdown isolated many people, leading to a lack of exercise, which in turn caused more mental stress or anxiety, and even lower immunity. Loss of group activity opportunities also removed the motivation for many individuals, as well as a loss of required resources.
In the other group reporting increased well-being, the reverse was seen, with increased sympathetic alterations. The study notes: “The fact that increased RMSSD, LF and HF (associated with decreased HR) were also observed post lockdown, is a marker of an effective and lasting improvement in cardiovascular fitness.” When both systems are hypertonic, the physical performance is at its peak, and this accounts for both LF and HF increasing at the same time along with a reduction in the heart rate at rest.
There was a moderate association between subjective well-being and HRV. The researchers say, “The more active people during the lockdown may have felt better. These later results emphasize the usefulness of HRV as a global index of heath in the general population.”
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.