A few days ago, there was an updated report on critical care for coronavirus patients in hospitals in England, Wales and Northern Ireland.
ICNARC report on COVID-19in critical care 17 April 2020.
Sometimes a single table can be illustrative, and this one gives the characteristics of those who end up in critical care. Covid-19 patients have been compared to viral pneumonia cases, and initially I went along with that comparison, finding relatively little difference, other than that men and Black and Asian patients (Indian and Pakistani) are more affected by Covid-19. I also noted that people who did not have co-morbidities requiring daily help with living were also to be found in critical care units.
This specific pandemic aside, there is a general problem in data analysis: what counts as a fundamental background measure? Age and sex are usually agreed to fit the bill, and the coronavirus shows differences, hitting the elderly and males more strongly. Social class? Race? Religion? All those are measured in many medical studies. Deciding what is fundamental is more problematic. Ideally it should be biological and likely to be causal.
What if one looks for something obvious to the naked eye?
Look at Table 1. What strikes you?
To my eye, it is striking that 74% of Covid-19 patients in intensive care are over-weight, compared with 60% for viral pneumonia patients.
This is very bad, but here is the context: in the UK in 2017/18, 62.0% of adults aged 18 and over were overweight or obese, up from 61.3% the previous year. So, it is bad, but that is the usual level of obesity in the UK population. Covid patients are higher even than that level.
(There is a case for saying that setting normal body weight index at 25 is too high. Hong Kong and Singapore use 23 as the cut-off for healthy weight, and when some researchers suggested that for the UK some time ago, it was rejected as being, although medically desirable, too demanding for public acceptance. Realpolitik.)
Rather than go on to find another set of explanations for the racial differences, why not see how over-weight each of the racial groups are? By the way, “Asian” in the UK means Indian sub-continent: Indian, Pakistani, Bangladeshi.
The Chinese control their body weight, Black citizens far less so, and all the others are at roughly at the same, somewhat lower levels of excess. Here are the same figures ranked:
Black people are twice as over-weight as Chinese people. Being too fat is bad for health, particularly leading to higher rates of type 2 diabetes, heart disease, stroke and some 10 cancers. The hazard ratio for being over-weight has been calculated at 1.5 so that the chance of dying in a defined period is about 50% higher. Smoking complicates the interpretation of results, so the weight figures are generally calculated for non-smokers.
Since obesity is so widespread in the UK, obesity is apt to be seen as the norm in biological terms.
Some researchers studying racial differences in health list the higher levels of these illnesses as separate causes which contribute to the observed racial differences. That is, they argue that some racial groups are facing both obesity and diabetes 2, without making too much of the fact that most of the latter disorder comes from the former behaviour. The other approach is to see those illnesses as largely caused by a failure to regulate food intake. From that perspective, apparent race differences could be differences of a different sort: not something which gives the virus preferential access to an opening in the genetic code, but a behavioural difference, (with a possible genetic cause), which then gives patients an additional burden so that they are less able to survive.
There is a complication, but it requires accepting that race is biologically real. The complication is that health problems seem to go up in Chinese people at BMI 23. Also, people from the Indian sub-continent start getting health problems at around that level. (In 1998 the US guidelines were that unhealthy weight began at BMI at 27.8 so bringing that down to 25 increased the apparent level of obesity, though it might have encouraged maintenance of healthy weight in some citizens).
The Nurses Health Study, for example, tracked patterns of weight gain and diabetes development in 78,000 U.S. women, to see if there were any differences by ethnic group. (1) All women were healthy at the start of the study. After 20 years, researchers found that at the same BMI, Asians had more than double the risk of developing type 2 diabetes than whites; Hispanics and blacks also had higher risks of diabetes than whites, but to a lesser degree. Increases in weight over time were more harmful in Asians than in the other ethnic groups: For every 11 pounds Asians gained during adulthood, they had an 84 percent increase in their risk of type 2 diabetes; Hispanics, blacks, and whites who gained weight also had higher diabetes risks, but again, to a much lesser degree than Asians. Several other studies have found that at the same BMI, Asians have higher risks of hypertension and cardiovascular disease than their white European counterparts, and a higher risk of dying early from cardiovascular disease or any cause. (2–4)
Researchers are still teasing out why Asians have higher weight-related disease risks at lower BMIs. One possible explanation is body fat. When compared to white Europeans of the same BMI, Asians have 3 to 5 percent higher total body fat. (5) South Asians, in particular, have especially high levels of body fat and are more prone to developing abdominal obesity, which may account for their very high risk of type 2 diabetes and cardiovascular disease. (6,7) In contrast, some studies have found that blacks have lower body fat and higher lean muscle mass than whites at the same BMI, and therefore, at the same BMI, may be at lower risk of obesity-related diseases. (8,9) (Keep in mind, though, that in the U.S., the prevalence of obesity is higher in non-Hispanic blacks than in non-Hispanic whites, so the overall burden of obesity-related diseases is still higher in this group.
Interesting what empirical enquiry throws up: if non-Hispanic blacks could maintain body weight at BMI 25 or so, they would have a lower risk of obesity-related diseases than whites of the same BMI. They are more muscular, a racial difference that means that blood test results for glomerular filtration rates have to be corrected by about 21%. The NHS has put this correction for “Black African descent” on all blood tests for a decade, without arousing any fuss. Evolutionary differences in bodies cause no problems when they are classified as medical.
Patients who are very over-weight may be too fat to breathe properly, an obvious possibility, since those extremely obese are often visibly too fat to walk properly, and are prone to knee problems. Additionally, or optionally, there may be something about fat which provokes and inflames cytokine storms.
Either way, the burden of fat is a burden to the patient, and given the demands of care, to society as well. Our herd is too fat for our own good. We may not like being described as a herd, but that’s what we are to a virus. Herd immunity, acquired by exposure or vaccination, denies the infectious agent the living warm hosts it needs to propagate. Denied stepping stones, some vulnerable bodies in the herd are relatively safe. The probability of infection is reduced, as it will be for a while because of the lockdown, and might continue to be for a while if masks and socially distancing and other restrictions are maintained. However, if the herd has many members who are too fat, they will be more at risk of all viruses, and more likely to have co-morbidities as a consequent of being over-weight.
At this point in an average academic discussion, it would be usual to list all the other possible factors which may be involved in racial differences: extended family structures, jobs which require interacting with the public, cramped housing, and so on. All those may indeed contribute to vulnerability to the disease. However, reducing weight is something which can be done simply by eating less.
One factor is enough for today.