Abstract

Background. Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), produces outcomes from mild illness to death. Although in-hospital prognostic factors have been widely reported, long-term mortality data are scarce, particularly from middle-income countries with relatively young populations. We therefore quantified one-year all-cause mortality and identified independent predictors in a large Turkish cohort. This information is critical for guiding follow-up strategies and allocating resources as the pandemic transitions to an endemic phase, and for developing prevention programs targeting high-risk groups.

Methods. All adults aged 18 years or older with polymerase chain reaction–confirmed SARS-CoV-2 infection admitted to Haydarpaşa Numune Training and Research Hospital between 1 March 2020 and 31 January 2021 were retrospectively included. Demographics, smoking status, and comorbidities coded by the ICD-10 were extracted from electronic records. Missing smoking data (3.75 %) were imputed by multiple imputation with chained equations. One-year survival status obtained from the death registry. Risk factors were examined by Cox proportional hazards models after confirming model assumptions.

Results. Among 14,975 patients (median age 40 years, interquartile range 28.5–52.2; 50.8 % male), 357 deaths occurred within 365 days, giving one-year mortality of 2.4 %. Non-survivors were older (71.8 vs 39.5 years), more often male (63 % vs 50.5 %), and had higher rates of diabetes mellitus, ischemic heart disease, heart failure, chronic kidney disease, and cancer. In multivariable analysis each additional year of age increased risk by 10 % (HR: 1.10). Other independent predictors were male sex (HR: 1.91), diabetes mellitus (HR: 1.28), ischemic heart disease (HR: 1.73), heart failure (HR: 1.44), chronic kidney disease (HR: 1.46), and cancer (HR: 2.06). Smoking was inversely associated with mortality (HR: 0.71) after inverse-probability weighting. Model discrimination was excellent (concordance index 0.89) and only cancer showed minor time-dependency early in follow-up. Bootstrap optimism correction confirmed robustness.

Discussion. One-year mortality after COVID-19 in this relatively young Turkish population was low yet clinically meaningful. Persistent excess risk among older adults, men, and patients with cancer or major cardiometabolic disease underscores the need for structured post-acute surveillance, prioritised vaccination boosters, and aggressive management of underlying conditions. The inverse association with current smoking is probably due to residual or unmeasured confounding and should not influence practice. These findings refine long-term risk stratification and can guide resource allocation as COVID-19 becomes an endemic threat; further rigorous external validation that incorporates vaccination status and viral variants is warranted.