Vaccination, regular exercise, and prevention of chronic lung disease reduce exacerbation of COVID-19 severity in northern Okinawa, Japan: A cross-sectional study

BACKGROUND: As at June 14, 2023, the coronavirus disease 2019 (COVID-19) pandemic had affected more than 767 million people and caused more than 6.9 million deaths worldwide. This study aimed to clarify the lifestyle factors that influence the exacerbation of COVID-19 severity. METHODS: This was a cross-sectional study of patients with COVID-19 whose severity classification of “moderate or severe” (COVID-19 exacerbation) was defined as an objective variable. The 1,353 participants were selected from 4,899 patients with COVID-19 between August 10, 2020 and December 10, 2022. Participants who underwent a specific health checkup before the date for a COVID-19 consultation were included. Using binominal logistic regression analysis, we evaluated the odds ratios (ORs) for COVID-19 exacerbation according to lifestyle-related factors. Limitations were discussed using a target trial emulation framework which clarifies problems in observational studies. RESULTS: The explanatory variables extracted as factors that exacerbated COVID-19 severity were gender (OR [man vs. woman]: 2.533, 95% confidence interval [CI] 1.484–4.322); age (OR [50s vs. 10s, 20s, or 30s]: 4.858, 95% CI 2.319–10.177; OR [60s]: 9.738, 95% CI 4.355–21.777; OR [70s + 80s + 90s]: 8.327, 95% CI 3.224–21.507); and comorbid chronic lung disease (OR [‘yes’ vs. ‘no’]: 2.892, 95% CI 1.227–6.818). The explanatory variables extracted as factors that reduce the severity of COVID-19 were hospital consultation year (OR [2022, predominantly Omicron variant prevalent vs. 2020, predominantly Alpha variant prevalent]: 0.180, 95% CI 0.058–0.559); number of vaccinations (OR [2 doses vs. 0 or one doses]: 0.223, 95% CI 0.114–0.436; OR [≥3 doses vs. 0 or one doses]: 0.090, 95% CI 0.035–0.229); regular exercise (exercising ≥2 days/week ≥30 minutes each at an intensity that causes a slight sweat for ≥1 year) (OR [‘yes’ vs. ‘no’]: 0.458, 95% CI 0.242–0.866). CONCLUSIONS: These results suggest the importance of vaccination, regular exercise, and prevention of chronic lung disease as measures against exacerbation of COVID-19 severity.