Does poor hygiene lead to better immunity against Covid-19? CSIR study answers

New Delhi
October 28, 2020 UPDATED: October 28, 2020 15:12 IST
Does low hygiene lead to better immunity against Covid-19?

A pre-print paper by the Centre for Scientific and Industrial Research (CSIR) has reiterated what US President Donald Trump has said about India and its hygiene standards.

The study by CSIR shows evidence to suggest that the country’s less than desirable hygiene levels have helped Indians fight Covid-19 better than other nations.

The study published in Medrxiv postulates that exposure to pathogens early in life protects people from allergic diseases later in their lives – the theory has been derived from “hygiene hypothesis”.

The study wished to explore if epidemiological data support the correlation between autoimmune diseases’ prevalence, sanitation parameters and how much of the variation in death per million due to Covid-19 is explained by the same.

“An interesting relationship between severity of Covid-19 outcome and several non-communicable disorders such as diabetes, hypertension, cardiovascular illnesses has been noted,” said the study.

“However, the non-communicable disease burden of a country and its apparent relation to CFR due to Covid-19 has not been explored in detail yet,” believe the co-authors of the study.

“As a large population with these disorders lives in the high Human Development Index (HDI) countries, co-morbidities with diabetes, hypertension, cardiovascular disorders and respiratory disorders might have emerged as important determinants of CFR due to Covid-19 in these countries.

“Similarly, the study found that people above the age of 65 are also believed to be at greater risk, with the percentage of such people being significantly more in the higher HDI countries. Thus, co-morbidities with non-communicable diseases and the fraction of people living above the age of 65, being skewed towards the high-income countries, offers possible explanations to the perplexing observation of CFR dichotomy among nations,” highlights the study.

On why there are more deaths in countries with higher GDP, this analysis opens up avenues to consider “immune training” with possibilities of microbiome therapies to supplement improved hygiene and sanitation practices. Hence, people who are more exposed to lower hygiene and sanitation standards may have developed greater “immunity training” than those who live in relatively cleaner environments.

Autoimmunity

One of the manifestations of better hygiene and safe sanitation practices in high GDP countries is the increased incidence in autoimmune disorders. It has been postulated that better hygiene practices could lower a person’s immunity and make the person susceptible to autoimmune diseases. Therefore it was tested if any of the autoimmune diseases showed an association with the LDM variable.

The study which is yet to be peer-reviewed mentioned: “We interestingly find a strong positive correlation with Multiple Sclerosis, Type 1 Diabetes Mellitus, Rheumatoid Arthritis and Psoriasis and a weaker correlation with Asthma.”

Safe sanitation

Lack of sanitation and poorer hygiene practices are known to be responsible for the higher communicable disease burden in the low GDP countries.

“It is, therefore, reasonable to expect that parameters describing safe sanitation and safe drinking water to be correlated negatively with the Covid-19 deaths. Surprisingly we find a contrary observation, where different sanitation parameters are correlated positively with the Covid-19 outcome. It is, therefore, perplexing to note the positive correlation of sanitation parameters.” states the study that is authored by CSIR head, Dr Shekhar Mande.

Immune training

Several studies have reported the protective role of parasitic/bacterial infections in bolstering human immunity, also referred to as immune training. “We observe that the prevalence of communicable diseases such as Malaria and Tuberculosis as well as parasitic diseases such as schistosomiasis, Onchocerciasis have a weak negative correlation with LDM.” the study states.

Upper respiratory diseases, however, show positive correlation which may be indicative of hyperactive immune response in individual suffering from such disorder. These intuitive observations related to communicable diseases with respect to Covid-19 deaths are suggestive of the role of “immune training” and the final disease outcome.