Introduction

The list of reasons why someone might suffer with long-covid is more or less the same as the list of reasons why anyone might have poor immune function in general. In most cases a careful health history can identify plausible causes of long-covid, as opposed to it being a mystery. If you cut your finger and it doesn’t heal there will be a reason. The same is somewhat true of recovery from SARS viruses, if you don’t recover well, it will be for some good reason.

Overtraining and Long Covid

Long-COVID can be defined as experiencing symptoms beyond four weeks from the initial COVID-19 infection without any other causes explaining its continuation. The precise way exercise might impact the persistence or worsening of COVID-19 symptoms remains unclear. However, some theories propose that physical activity could trigger system imbalances or inflammation, worsening physiological issues associated with long-covid. Moreover, engaging in activity could increase stress or place additional metabolic demands on already compromised systems in people with long-term, potentially prolonging symptoms or impeding recovery.

Poor Diet and Long Covid

The exact mechanism of action that causes long-covid isn’t fully understood. However, theories surrounding chronic inflammation, oxidative stress and gut dysbiosis play a crucial role in the persistence of COVID-19. Due to COVID being a viral infection, it can be assumed that a diet supporting healthy immune function will allow for higher resilience against COVID-19 and the probability of it developing into long-covid. Individuals deficient in vitamins C, D and zinc are at higher risk of frequency and severity of infection. Diets that have excess refined sugars, saturated fats, and processed foods cause chronic inflammation and oxidative stress, in turn predisposing people to prolonged periods of infection. 

Asthma and Long Covid

Long-covid triggers inflammation and lung damage, making airway hyperresponsiveness worse in people with asthma. This can result in breathing problems and reduced lung function. The increase in asthmatic episodes further fuels inflammation and immune dysregulation, creating a positive feedback loop of breathing difficulties. Additionally, asthmatics who have been taking medications like corticosteroids for extended periods can suppress the immune response, further compromising immunity.

Early-Life Stressors and Long Covid 

Stress is a well-documented cause of immunosuppression, and even past stressors can cause susceptibility to poor recovery from viruses in the present day. Early life stressors can significantly impact how individuals experience and cope with COVID-19. Those with a history of early life stressors (aka childhood trauma) may have heightened stress responses, which can exacerbate symptoms and delay recovery. This can also influence health behaviours, such as sleep patterns, diet, and exercise, which are crucial for managing long-term symptoms. Additionally, early life stressors can contribute to mental health challenges, such as anxiety and depression, which are common in long-covid patients. 

Viral Persistence and Long Covid

Long-covid, characterised by persistent symptoms post-SARS-CoV-2 infection, is attributed to viral persistence mechanisms. The virus may evade complete clearance, lingering within host cells or tissues. This persistence perpetuates immune activation and inflammation, driving prolonged symptoms. Remnants of a virus have the potential to cause reactions resulting in long-lasting inflammation of the tissues and even autoimmune responses. When the virus lingers in the body, it disturbs homeostatic balance within cells. This can trigger the perpetual activation of immune cells, making symptoms worse.

Post-Intensive Care Syndrome (PICS) and Long Covid

Post Intensive Care Syndrome (PICS) contributes to the emergence of long-covid by mimicking psychological and emotional difficulties seen in individuals following a severe illness. Signs of PICS include muscle fatigue, cognitive impairments, feelings of anxiety and depression. These symptoms can mirror those seen in long-covid patients. Chronic inflammation, organ failure and extended periods of immobility during severe illness can worsen body system imbalances and slow down recovery, leading to ongoing long-term COVID 19 symptoms. Furthermore, the psychological trauma of surviving a life-threatening condition can weaken normal immune system function. Identifying and managing PICS in patients with long-covid is crucial to ensure care and enhance long-term health outcomes.

Obesity and Long Covid

Obesity is a prime causative factor of various metabolic dysfunctions, chronic inflammation, and multi-organ impairment. Recent evidence suggests that individuals with a body mass index (BMI) over 30 are at increased risk of severe infection and poor outcomes from COVID-19. Obesity is often accompanied by other comorbidities such as hypertension, diabetes, and cardiovascular disease, which are also risk factors for developing long COVID. Excessive subcutaneous fatty tissue around the chest and abdomen restricts lung expansion and decreases vital capacity. Shallow breathing in obesity promotes an increased risk of developing respiratory tract infections. Furthermore, individuals with obesity had higher SARS-CoV-2 viral loads in the upper respiratory tract, allowing for uncontrolled virus replication in the upper respiratory tract and an inefficient immune response in individuals with obesity.