New research from the United Kingdom suggests several factors that increased the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection involved higher alcohol use, Asian/Asian British ethnicity, and obesity. In addition, moderate but not vigorous exercise of more than 10 hours a week was associated with lower susceptibility to infection.
The study “Determinants of pre-vaccination antibody responses to SARS-CoV-2: a population-based longitudinal study (COVIDENCE UK)” was published on the preprint medRxiv* server.
Study: Determinants of pre-vaccination antibody responses to SARS-CoV-2: a population-based longitudinal study (COVIDENCE UK). Image Credit: NIAID
Details on the COVIDENCE UK study
The COVIDENCE UK observational study began on May 1, 2020, where researchers measured the rate of COVID-19 infection in people 16 years and older living in the United Kingdom.
Participants completed an online questionnaire that asked questions regarding potential COVID-19 symptoms experienced since February 1, 2020, any COVID-19 tests results, if available, and self-reporting of any potential COVID-19 risk factors. A total of 88 potential risk factors for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were studied.
Follow-up questionnaires recorded information on positive COVID-19 test results and symptoms for acute respiratory infection.
Another part of the study involved analyzing antibody titers from participants. Antibody testing began in November 2020 and included participants who were not vaccinated or who gave dried blood spot samples on or before the date of their first COVID-19 vaccination.
Of the 11,130 participants involved in the antibody study, there were 1,696 who tested positive for SARS-CoV-2 antibodies. About 70% of seropositive cases were women, and 95.7% identified as White with a median age of 62.3.
Factors associated with increased risk of COVID-19 illness
A total of 28 factors were independently correlated with the risk of SARS-CoV-2 seropositivity.
There were four main factors — people of Asian ethnicity, being a frontline healthcare or social care worker, international travel, and having a high BMI (≥25 kg/m²) — that were strongly associated with increased risk of COVID-19 infection and high antibody titers in infected patients.
Other factors such as low educational level, sex hormone therapy, light physical activity, use of vitamin D supplements, and increased drinking (15 or more units per week) were correlated with increased infection.
“High levels of alcohol intake are known to negatively affect immune response through several mechanisms, which supports our finding of increased risk among participants consuming more than 15 units of alcohol a week,” explained the research team.
When it comes to exercise levels, the researchers observed a decreased risk of COVID-19 when participants exercised for more than 10 hours per week.
Combined IgG, IgA and IgM anti-S titers in seropositive participants by ethnicity, frontline worker status and COVID-19 severity Log-transformed anti-spike IgGAM ratios are shown for all seropositive participants (n=1774) by ethnic group (A), frontline worker status (B), and COVID-19 severity (C), with horizontal lines showing median and IQR. (A) ‘Black’ indicates people of Black, African, Caribbean, and Black British origin. ‘Mixed or other’ indicates people of mixed, multiple, or other ethnic origins. (C) COVID-19 severity was classified as ‘asymptomatic’ (non-hospitalized participants who either did not report any symptoms of acute respiratory infection or whose symptoms were classified as having <50% probability of being due to COVID-19); ‘symptomatic, not hospitalised’ (non-hospitalized participants reporting symptoms of acute respiratory infection that were classified as having ≥50% probability of being due to COVID-19); and ‘hospitalised’ (participants hospitalized for treatment of COVID-19). IgGAM=IgG, IgA, and IgM.
The researchers hypothesize that there could be a J-shaped relationship between the amount of exercise and infection risk, which could explain why vigorous exercise did not receive the same benefits as moderate exercise. For example, moderate exercise can increase the immune response, but drawn-out high-intensity exercise can increase one’s susceptibility to infection.
Passive smoking and prescribed paracetamol use were both associated with reduced risk of COVID-19 illness.
A limitation to the research study is the make-up of the participants. The cohort was self-selected, so several groups, including people younger than 30, people of low socioeconomic status, and non-White ethnic groups, were underrepresented.
Another study limitation involved the inclusion of asymptomatic infections during the titer analysis. Because of the inclusion, they could not adjust for the timing of infection onset, making it difficult to learn how antibody responses changed over time.
Because this was an observational study, there is always the chance that some associations may be explained by other variables not measured in the study. For example, the researchers found that passive but not active smoking lowered the risk of seropositivity compared with people who never smoked. However, this result should be taken with caution because of the dangers associated with smoking — unless a plausible protective mechanism can be established.
Future research should involve modifiable risk factors for seropositivity, antibody titers, and other factors correlated with protection from COVID-19 illness to better understand what kind of person is most at risk for reinfection and what preventative measures can be taken.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.