# Factors Related to Mortality in Patients with COVID-19 during the Early Phase of the Pandemic in Japan: An Observational Study Using the Osaka Prefectural Novel Coronavirus Response Status Management System

## TL;DR

This study identifies factors linked to higher mortality in early-phase COVID-19 patients in Japan, including age, sex, and underlying health conditions.

## Contribution

The study provides insights into early pandemic mortality factors using detailed regional data from Osaka, Japan.

## Key findings

- Male sex was associated with a significantly higher mortality risk compared to female patients.
- Older age groups (70-79 and ≥80 years) had much higher mortality odds than younger individuals.
- Underlying diseases increased mortality risk, with specific disease categories showing stronger associations.

## Abstract

Elucidating the epidemiological picture in the early phase of a pandemic is crucial to strengthening preparedness and public health responses to future emerging infectious diseases. Using data from the “Osaka Prefectural Novel Coronavirus Response Status Management System,” we evaluated factors associated with mortality among patients with novel coronavirus disease 2019 (COVID-19) in Osaka Prefecture, Japan.

The study periods were from January 29 to June 13, 2020 (first surge), from June 14 to October 9, 2020 (second surge), and from October 10 to December 24, 2020 (up to the middle of the third surge). The odds ratios (ORs) and 95% confidence intervals (95% CIs) for mortality were calculated using logistic regression models.

Of the 14,864 patients with COVID-19 (8,207 men, 6,657 women) registered, 297 (2%) died. The ORs for mortality were significantly higher in men (OR = 2.00, 95% CI = 1.54-2.60) than in women, in 70- to 79-year-olds (OR = 25.4, 95% CI = 16.8-38.2) and ≥80-year-olds (OR = 78.1, 95% CI = 53.3-114) than in 0- to 69-year-olds (P for trend < 0.001), and in those with underlying diseases (OR = 1.74, 95% CI = 1.34-2.27) than in those without. The ORs for the second surge (OR = 0.42, 95% CI = 0.31-0.57) and third surge (OR = 0.41, 95% CI = 0.29-0.58) decreased compared with the first surge. Detailed evaluation of underlying diseases by time period showed that “Diseases of the blood and blood-forming organs and certain disorders involving immune mechanisms,” “Endocrine, nutritional, and metabolic diseases,” “Diseases of the genitourinary system,” and “Diseases of the respiratory system” were associated with increased risk of mortality.

Among those affected early in the COVID-19 epidemic, male sex, older age, first-surge infection, and underlying medical conditions were significantly associated with mortality. Our findings are expected to provide a useful reference for future countermeasures in the early stages of pandemics involving unknown emerging infectious diseases.