By Neha MathurReviewed by Aimee MolineuxFeb 8 2023

In a recent study published in JAMA Internal Medicine, researchers performed a prospective cohort study among 1981 female nurses to investigate whether maintaining a healthy lifestyle decreases the risk of post–coronavirus disease 2019 (COVID-19) condition (PCC) following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

They assessed six modifiable healthy lifestyle factors, body mass index (BMI), alcohol consumption, smoking, diet, exercise routine, and sleep. The follow-up with all the eligible participants continued for more than a year from April 2020.

Background

Over 23 million Americans have developed PCC, which makes it a major public health burden. Its increasing prevalence worldwide, especially among unvaccinated and severely ill individuals, calls for a better understanding of PCC causes. A healthy lifestyle benefits both innate and adaptive immunity. Thus, adopting and adhering to healthy lifestyle habits (e.g., a balanced diet and adequate sleep) could lower the likelihood of severe COVID-19 and mortality. Nevertheless, there is an urgent need to understand the association between adopting these habits before SARS-CoV-2 infection and the risk of developing PCC.

About the study

In the present study, researchers administered seven sequential surveys between April 2020 and November 2021 to identify female nurses with confirmed SARS-CoV-2 infection and PCC characterized by a minimum of four weeks of symptoms. Additionally, they explored whether a preinfection healthy lifestyle was associated with fewer PCC symptoms.

The researchers considered these healthy lifestyle habits - never smoking, alcohol consumption between five to 15 grams per day, a healthy diet with a higher score (>40) on the Alternate Healthy Eating Index–2010, and at least 150 minutes per week of moderate to vigorous exercise.

The study cohort comprised 32249 female nurses enrolled in the Nurses’ Health Study II, who responded to the COVID-19 substudy baseline and other survey questionnaires. All these women, residents of the United States of America (USA) aged between 25 and 42 years, reported pre-SARS-CoV-2 infection lifestyle habits for two years, 2015 and 2017.

The team used Poisson regression to estimate PCC relative risk (RR) correlated with six healthy lifestyle habits. Also, they calculated the population attributable risk percentage (PAR) that denoted the proportion of PCC cases that hypothetically would not have occurred if all participants were in the low-risk group. Finally, they conducted ten sensitivity analyses.

Results

After 19 months of follow-up, the final study cohort had 1981 female nurse participants having an average age of 64.7 years. These participants returned the 2017 questionnaire within an average of 35 months of SARS-CoV-2 exposure. Of participants who reported a positive SARS-CoV-2 test during follow-up, 44% reported PCC. Among these, 87% experienced PCC symptoms lasting two months, and 56.5% also experienced occasional PCC-related daily life deficits.

The researchers noted that all six healthy lifestyle factors were associated with a lower PCC risk, with BMI between 18.5 to 24.9 and sleep of seven to nine hours per day being the most strongly associated factors. They outlined three biological mechanisms to explain the observed associations.

First, all six unhealthy lifestyle choices increase the risk of chronic inflammation that might have predisposed affected individuals to excessive release of cytokines after infection. Together, this increased the risk of long-term complications in multiple organs. Second, these habits might have disturbed adaptive autoimmunity, as seen in PCC-affected individuals.

Third, these habits, such as smoking and excessive alcohol intake, predispose people to blood clotting anomalies, another biological change in people experiencing PCC. Among PCC-affected study participants with higher preinfection healthy lifestyle scores, all COVID-19 symptoms were less prevalent, except for smell/taste disorders and headache.

Conclusions

The study results indicated that adherence to a healthy lifestyle had a dose-response association with the risk of PCC, accounting for sociodemographic factors and comorbidities. Given that these associations were causal, participants with five or six healthy lifestyle habits before contracting SARS-CoV-2 infection would have been at a 50% lower risk of PCC equivalent to combined PAR of all six lifestyle factors, i.e., 36%. Nevertheless, maintaining a healthy weight and taking adequate sleep conferred the greatest benefit for PCC prevention.

Future research should investigate whether adopting healthy lifestyle habits could decrease the risk of developing PCC and similar chronic diseases after COVID-19 or reduce their severity.