We already know that the elderly and people with underlying diseases tend to be more severe after suffering from the new coronavirus disease (COVID-19). As the epidemic develops globally, more clinical phenomena suggest another potential risk factor for severe illness: overweight and obesity.
In response to this topic, Nature Reviews Endocrinology, a sub-Journal of Nature, has recently published a review article in collaboration with scholars from the German Diabetes Research Center and Harvard University. Combining this review article and related research, we briefly review the existing evidence of obesity and COVID-19 severe risk.
Early research data
A retrospective study of 24 critically ill patients diagnosed in the Seattle area of the United States, published in the New England Journal of Medicine, is one of the earliest studies to report BMI data. Among them, 3 patients had normal BMI, 7 were overweight, 13 were obese, and 1 had missing data. Although the sample size is too small for meaningful statistical analysis, it can still be observed that 85% of obese patients require mechanical ventilation and 62% of obese patients die, which is significantly higher than non-obese patients (the proportion of corresponding patients 64% and 36% respectively).
Subsequently, data from different countries and regions further supported concerns about the impact of obesity.
Among the 383 COVID-19 patients in Shenzhen, China, overweight was associated with an 86% increase in the risk of severe pneumonia compared with normal-weight patients, and the risk of severe disease was 142% higher in obese patients.
The data of 3,615 confirmed patients published in the Clinical Infectious Diseases by the New York University School of Medicine shows that the hospitalization rate of obese patients (BMI ≥ 30 kg / m2) has more than doubled among people under 60 years of age. The risk of requiring intensive care has also increased significantly.
In another retrospective analysis of 4013 COVID-19 patients in New York, BMI> 40 kg / m2 is the second largest independent predictor of hospitalization risk, with a 6-fold increase in risk, second only to aging. The researchers noted, "It is worth noting that the chronic disease most closely related to critical illness is obesity, whose risk is much higher than cardiovascular or lung disease."
A university hospital in Lille, France, reported data on 124 COVID-19 patients in the journal Obesity, showing that BMI ≥35 kg / m2 is associated with a 6.36-fold increase in the risk of requiring invasive mechanical ventilation. This association is not affected by Whether the patient has the influence of co-morbidity. What surprised the researchers is that the only risk factor for many young patients is obesity, and the disease progresses very quickly.
Potential ways obesity affects the risk of severe illness
Previous studies on obesity and respiratory diseases suggest that mechanisms that mediate high-risk mechanisms include respiratory mechanics damage, increased airway resistance, and gas exchange function damage, as well as low respiratory muscle strength and low lung capacity. Pathophysiological characteristics.
Regarding COVID-19, the author of the above-mentioned French Lille study believes that the "culprit" of obesity leading to serious risk is inflammation. His colleagues found that inflammation-related systemic fibrin deposition may affect blood oxygen transport during autopsy, which helps Explain the reasons why some obese patients do not perform well after receiving mechanical ventilation.
New York University School of Medicine research authors also agree that "obesity is a pro-inflammatory disease", and some inflammatory markers are very important in distinguishing critically ill patients, such as the early rise of C-reactive protein and D-dimer. There is a strong correlation between mechanical ventilation or death.
The authors of the "Nature" review article suggested the association between obesity and other complications. Overweight and obese people are also often associated with related metabolic health problems, such as abnormal blood pressure, blood lipids and blood sugar. Cardiovascular diseases, diabetes, chronic kidney disease and other common chronic diseases are also closely related to obesity. In addition, they specifically pointed out that the common insulin resistance of obese people is also one of the important independent determinants of abnormal metabolic health, poor cardiac function and cardiovascular disease mortality.
The Paradox of Obesity
However, in previous studies on obesity and pneumonia, the phenomenon of "survival paradox" has also been observed-although obesity increases the risk of pneumonia and the difficulty of intubation and ventilation after illness, the incidence of obesity in pneumonia patients The risk of death may be reduced.
A meta-analysis by Shanghai Changzheng Hospital on the data of nearly 3 million patients showed that the risk of pneumonia in overweight and obese people increased significantly by 33%. For every 5 kg / m2 increase in BMI, the risk of pneumonia increased by 4%. The overweight and obese people have a 13% lower risk of death. For every 5 kg / m2 increase in BMI, the risk of death decreases by 5%.
Potential countervailing factors for this phenomenon include that obese patients may receive more aggressive treatment, and that their own metabolic reserves are relatively high, which may also eliminate certain metabolic and inflammatory stress.
Although most of the previous COVID-19 studies have not analyzed the effects of obesity, we also see that relevant evidence is gradually accumulating.
The author team of "Nature" believes that the existing evidence suggests that high BMI may be an important risk factor for the development of severe illness. Considering that obesity is the main risk factor for a variety of comorbid diseases and is generally related to metabolic health abnormalities, in order to better assess the complications and severe risks of COVID-19 patients, and to determine the independent effects of BMI and related metabolic characteristics, it is recommended In addition to the routine in-hospital examination indicators, measurement of physical and metabolic indicators such as BMI, waist and hip circumference, blood glucose and insulin levels were increased. At the same time, the author team calls for more reports to improve our understanding of COVID-19 and better improve our disease prevention and diagnosis.