Summary

A study published in the Brain, Behavior, and Immunity journal indicates that maintaining a healthy lifestyle significantly reduces the risk of severe COVID-19 requiring hospitalization, with fitness and weight management being key factors.

Abstract

The research, led by Professor Mark Hamer and colleagues, analyzed data from 387,109 participants in the UK Biobank study and found that lifestyle behaviors such as physical activity, smoking, alcohol consumption, and body weight have a dose-dependent impact on the likelihood of hospitalization due to COVID-19. Individuals with a lifestyle score of 5 or more had a 4.41-fold increased risk of severe disease. The study highlights that over half of the COVID-19 hospitalizations could potentially have been prevented through healthier lifestyle choices, with being overweight or obese identified as the most significant risk factor, followed by smoking and physical inactivity. The study also suggests that the underlying mechanism linking unhealthy behaviors to severe COVID-19 may involve chronic, low-grade inflammation, as indicated by elevated levels of C-reactive protein.

Opinions

The authors believe that lifestyle interventions could substantially reduce the burden of severe COVID-19 cases.
They suggest that the risk of severe COVID-19 is not only influenced by individual lifestyle factors but also by the cumulative effect of multiple unhealthy behaviors.
The study posits that addressing modifiable risk factors, such as obesity and physical inactivity, could be crucial in mitigating the impact of pandemics like COVID-19.
The research team speculates that some participants may have changed their lifestyle behaviors since the baseline measurement, which could affect the study's findings.
They acknowledge that the study's observational nature means that the population attributable fraction (PAF) might be an overestimate, and interventional studies are needed for confirmation.
The authors conclude that adopting simple lifestyle changes could significantly lower the risk of severe COVID-19 infection.

Being Fit Prevents Severe Covid-19 in a Dose-Dependent Manner

Half of Covid-19 hospitalizations could’ve been prevented by fostering a healthy lifestyle.

Mark Hamer, a professor of sport and exercise medicine, and his colleagues at UK institutions recently had their paper, “Lifestyle Risk Factors, Inflammatory Mechanisms, and COVID-19 Hospitalization: A Community-Based Cohort Study of 387,109 Adults in UK,” published in the Brain, Behavior, and Immunity journal.

This is the first study to investigate how much do health behaviours affect the risk of being hospitalized for Covid-19. And how many cases could have been averted if at-risk individuals fostered a healthier lifestyle.

Poor Lifestyle Score

The study recruited 387,109 people from the UK Biobank study, of whom 760 (0.2%) were hospitalized for Covid-19. Analyzing the health behaviours of these 760 patients, they found that a lifestyle score of ≥5 lead to 4.41-fold increased risk — or 4.41 times as likely — for hospitalization.

The poor lifestyle score is calculated based on:

Smoking history (0=never; 1=past; 2=current).
Physical activity (0=meeting guidelines; 1= active but below guideline; 2=sedentary). Guidelines were ≥150 minutes/week of moderate-to-vigorous physical activity or ≥75 minutes/week of vigorous activity.
Alcohol (0= intake within guidelines; 1= never or very occasional exceeding guidelines; 2= intake exceeding guidelines). Guidelines were <14 units in women and <21 units in men.
Obesity or BMI >30 (0=healthy weight; 1=overweight; 2 = obese).

A poor lifestyle score ≥5 would look like an overweight person who drinks a lot of alcohol, rarely exercise, and smoke cigarettes (1+2+1+2=6). Or it could be an ex-smoker who is inactive, overweight, and sometimes a heavy drinker (1+2+1+1=5).

To reiterate, a poor lifestyle score of ≥5 increased the risk of severe Covid-19 in need of hospitalization by >4 times compared to the optimal lifestyle score of 0. And this effect is dose-dependent with poor lifestyle scores of 1, 2, 3, and 4 leading to 1.58 times, 2.73 times, 2.76 times, and 3.12 times increased risk, respectively.

Individual Lifestyle Factor

Professor Hamer et al. then looked at each health behaviour individually. Adjusting for age, sex, and each health behaviour (to avoid overlapping or compounding effects), they calculated that:

Physical inactivity increased hospitalization risk by 1.32 times.
Smoking increased hospitalization risk by 1.42 times.
Obesity increased hospitalization risk by 2.05 times.
Heavy alcohol intake, alone, did not increase hospitalization risk.

Population Attributable Fraction (PAF)

PAF refers to the measure of how much of cases could be averted if at-risk individuals modified their risk. A PAF of 10%, for example, means that 10% of cases could have been avoided if the risk factor was addressed earlier. In this case of Covid-19 hospitalization:

PAF of active smoking was 13.3%.
PAF of physical inactivity was 8.6%.
PAF of overweight or obesity was 29.5%.
PAF of the three combined was 51.4%.

This means that, in the UK Biobank cohort, poor lifestyle choices of cigarette smoking, sedentary behaviour, and being overweight/obese contributed to over half of Covid-19 hospitalizations. Put it the other way, half of the severe Covid-19 cases could have been avoided by cultivating a healthier lifestyle.

Underlying Mechanism

The current study also examined the levels of C-reactive protein (CRP), a marker of chronic, low-grade, pro-inflammatory state. For each quintile increase in CRP levels, there was a dose-dependent increase in the risk of hospitalization — i.e., 1.18, 1.32, 1.48, and 1.47 times, respectively.

Adjusting for CRP levels blunt the effect estimates of the lifestyle score on the hospitalization risk by 10–16% — “suggesting a possible mediating effect,” the authors wrote. This finding indicates that the reason unhealthy behaviours increase the risk of severe Covid-19 is, partly, due to unresolved chronic, low-grade inflammation in the body.

A Few Things to Consider

As with any other studies, results should be interpreted in light of its limitations:

Baseline health behaviours were measured during the UK Biobank study in 2010. Some participants may have reversed their behaviour after that. The heavy alcohol consumption group that had no increased risk of hospitalization, for example, may have “stopped drinking due to prescribed medication and underlying health conditions,” the authors speculate.
Some covariates were not controlled for — i.e., disease comorbidity, education, and ethnicity.
Cases of Covid-19 being treated outside of hospitals were not studied.
This study is observational and not interventional, so the calculated PAF may be an overestimate.

To Wrap Up

In this cohort study in the UK, unhealthy lifestyle choices is a major risk factor for severe Covid-19 in need of hospitalization. Being overweight or obese was the greatest risk factor, followed by smoking and sedentary behaviour. Heavy alcohol consumption, by itself, was not a risk factor in this study.

However, the overall fitness— encompassing weight, smoking, exercise, and alcohol — has a compounding or cumulative effect on the risk of Covid-19 hospitalization. And this is partly due to the underlying chronic, low-grade inflammation. Importantly, the risk is dose-dependent; more unhealthy behaviours lead to greater risk.

Looking at the bright side, it also means that a healthy lifestyle could prevent cases of severe Covid-19 by about 50% of the time, as shown by the PAF score. “Adopting simple lifestyle changes could lower the risk of severe COVID-19 infection,” Professor Hamer and his team concluded.