With Covid-19 likely to linger for some time yet, PROFESSOR FRANCES WILLIAMS from King’s College London and her team, ROGER COMPTE BOIXADER and ISABELLE GRANVILLE SMITH, explain how the pandemic has affected rates of low back pain and discuss whether patients with long Covid may be more susceptible to chronic low back pain.
The pandemic has increased back pain incidence
We have all experienced significant and abrupt disruption to routines both at work and home because of Covid lockdown and restrictions on freedoms. Those with low back pain have reduced seeking medical attention, management, and support – but back pain cases have begun to escalate, perhaps because many are working from home in sub-optimal conditions and lack the exercise of traveling to and around the workplace.
Up to half of the people responding to questionnaires throughout the UK, Europe, and the US have experienced new back pain episodes since the pandemic began. The SARS-CoV-2 virus induces the illness Covid-19, which is associated with symptoms in many different organ systems. At the beginning of the pandemic, Covid-19 was thought to be mainly a respiratory disorder. However, nearly two years down the track it is recognised that it may affect multiple body systems.
Myalgia or widespread muscle pain and unusual joint pain are commonly reported symptoms of Covid-19. Such pain likely reflects the immune response to viral infection, including the production of cytokines and other inflammatory mediators. These have been well documented in Covid-19 patients as well as multiple other infections including flu. The production of autoantibodies has been detailed in some patients and is the subject of current research efforts.
How the body produces these antibodies is influenced by our genetic make-up, and our genes may be responsible for the type of response we have to a virus. Genetic diversity in Covid-19 patients has been associated with illness severity and outcome. But that is to be expected. In fact, it has long been recognised that our response to viral or bacterial infection is regulated through our host genetics. Individual differences and genetic predisposition are currently the core hypotheses of many studies aiming to decipher the response to SARS-CoV-2 and the development of long Covid.
Long Covid, or post-acute Covid syndrome, describes symptoms that persist past the usual infective period of two or three weeks. “Long” when referring to Covid-19 symptoms has differed between research groups, but now the National Institute for Health and Care Excellence (NICE) has reasonably proposed symptoms lasting beyond 12 weeks from the first day of symptoms.
This is because many viral infections have effects that last for several months as a normal part of the illness. The Covid Symptom Tracker app from King’s reports that around 5% of people logging symptoms on the app have gone on to become “long-haulers”. Other estimates are higher – a study from Imperial College London including half a million participants found as many as 37.7% of Covid-19 patients still experience one or more symptoms at 12 weeks. Different methods of data collection and interpretation of symptoms may explain the dissimilarity of these estimates. Nevertheless, with infection so common in the general population and new infections continuing, the number having long Covid in the UK is likely to increase.
People experience long Covid in different ways, and there are currently no tests or biological markers for the condition. People tend to experience long Covid symptoms in waves or intermittently – some days patients seem to be recovering, and the next they are so sick they can barely get out of bed. An additional problem is that only around half of those who have been sick with Covid-19 display any immunity, meaning re-infection is possible, which may be confused with long Covid. As the symptoms of Covid-19, long-haul symptoms are extremely varied. Below are the more commonly reported symptoms:
- breathlessness or shortness of breath
- poor sleep
- mood disorders: anxiety/depression
- heart palpitations/chest restriction or pain
- unusual muscle pains
- poor concentration or “brain fog”
- loss of, or altered sense of, smell or taste
- persistent cough.
Two of the most common symptoms of long Covid are fatigue and myalgia. Fatigue is far more debilitating than feeling tired or run down, it can be so extreme that people may be unable to get out of bed. Myalgia can range from a dull, persistent ache to a very sharp, nerve-type pain.
Post-acute Covid syndrome, like SARS-CoV-2, can affect several biological systems at once. Two post-Covid symptom clusters have been identified; the first dominated by respiratory symptoms and the second by fatigue complaints. Such findings may go some way toward helping researchers untangle whether post-acute Covid syndrome is really one disorder – or in fact, several different post-viral illnesses.
Who gets long Covid?
The short answer is anyone can get long Covid, but there is a slightly increased risk in certain groups. The UK government and the National Institute for Health Research (NIHR) have supported the Longitudinal Health and Wellbeing National Core Study aimed at understanding how and why long Covid comes about. Diagnosing and treating physical and psychological long Covid triggers is an important goal of the work. Trials of current medications used for other conditions and collaborative work with many clinic centers are included within the project.
Twin research at King’s College London is contributing to one of these longitudinal cohort studies; it will use electronic health records and other patient data about Covid-19 and long Covid for more than one million participants. An important new finding of the study noted that as age increases, up to 70, so does the occurrence of long Covid. There were also slightly higher rates of long Covid seen in the following:
- those with a high BMI (overweight or obese)
- people with asthma
- people with poor mental health (pre-pandemic)
- people with poor physical health (prepandemic).
Other research has found patients who had more serious Covid-19 illnesses and people who smoke or vape are more likely to develop long Covid. Poor pre-pandemic mental health and general health are new conditions to be associated with long Covid. In the future, we may gain a better understanding of how the contributions from genetic variability, general health, and socio-economic characteristics lead patients to experience Covid-19 and if they develop long Covid.
Are back pain and long Covid linked?
Back pain is common, but the good news is that there is no current evidence linking long Covid with an increased risk of developing or experiencing back pain. For example, the Covid symptom tracker app data, which early in the pandemic showed loss of smell and taste as a significant predictor of infection, has shown the proportion of people reporting unusual muscle aches and pains are similar for those with both Covid-19 and long Covid.
As early as April 2020, research from China reported those with rheumatic diseases, which are mostly autoimmune, were more likely to experience higher levels of inflammatory markers – akin to that experienced during a rheumatological flare as well as worse respiratory distress or failure than their counterparts without the rheumatic disease. However, autoantibodies can be produced during Covid-19 by people without autoimmune disorders and may be found to be a precursor to long Covid muscle and joint pain. The good news is that despite great initial concern autoimmune patients would be at increased risk from SARS-CoV-2, that has not been the case.
Covid-19 inflammation can, in rare cases, produce myositis or painful swelling of the tissue around the spine. This could be a potential cause of back pain during long Covid. However, we are still in the early days of understanding the long-term effects of Covid on the body and the prognosis for long-haulers. Research is currently focused on understanding individual responses to the virus and long Covid. Trials using existing medications, such as blood thinners and statins, are also being explored to treat long Covid. We must continue collecting data to better understand the risks of long Covid – and the reasons why it develops.