More cognitive issues, fewer heart problems after COVID-19 vs flu hospitalization in Asians

Individuals hospitalized for COVID-19 vs seasonal influenza face a greater risk of cognitive impairment and fatigue but a lower risk of cardiac disorders as long-term consequences of infection, according to a retrospective population-based cohort study in Singapore.

Analysis of data from the national healthcare-claims database showed an increased hazard for long-term cognitive and fatigue sequelae following COVID-19 hospitalizations vs influenza hospitalizations. Specifically, the risk of cognitive/memory impairment was 34-percent higher (adjusted hazard ratio [aHR], 1.34, 95 percent confidence interval [CI], 1.08–1.68; p<0.001), while that of fatigue/malaise was 75-percent higher (aHR, 1.75, 95 percent CI, 1.23–2.50; p<0.001). [Int J Infect Dis 2025;doi:10.1016/j.ijid.2025.107946]

The risk increase was even more pronounced among unboosted COVID-19 patients vs unvaccinated influenza patients, with a 67-percent greater risk of cognitive/memory impairment (aHR, 1.67, 95 percent CI, 1.27–2.19; p<0.001) and 77-percent greater risk of fatigue/malaise (aHR, 1.77, 95 percent CI, 1.18–2.64; p<0.001).

Conversely, the risk of cardiac sequelae was lower by 23 percent following COVID-19 vs influenza hospitalizations (aHR, 0.77, 95 percent CI, 0.64–0.92; p<0.001).

Consistent results were seen for the risk of any cardiac diagnosis/symptom between unboosted COVID-19 patients and those who were unvaccinated against influenza (aHR, 0.80, 95 percent CI, 0.68–0.94]; p<0.001), as well as the risk of other cardiac disorders (eg, heart failure) between boosted COVID-19 patients and those who were vaccinated against influenza (aHR, 0.58, 95 percent CI, 0.39–0.86; p<0.001).

Taken together, these data indicate that vaccination against both COVID-19 and influenza remains important during endemicity, given the continued transmission of COVID-19 and post-pandemic resurgence of influenza, the investigators said.

“Better understanding of differences in pathophysiological mechanisms underlying postinfectious sequelae for various respiratory viral infections (RVIs) may guide potential treatments and therapeutic interventions,” they noted, adding that clinicians must closely monitor for varied long-term complications after RVI hospitalization.

The analysis included 70,628 adults hospitalized for COVID-19 during Omicron-predominant transmission (1 January 2022–3 September 2023) and 10,454 adults hospitalized for seasonal influenza (1 January 2017–3 September 2023) in Singapore. Most of the patients in the COVID-19 and influenza cohorts, respectively, were at least 60 years of age (66 percent and 54.7 percent), female (51.0 percent and 54.7 percent), Chinese (74.1 percent and 58.1 percent), and were not immunocompromised (81.6 percent and 87.5 percent).

In the COVID-19 cohort, 71.6 percent of patients had received a booster dose. Meanwhile, in the influenza cohort, only 11.4 percent of patients had been vaccinated. A small percentage of patients required ICU-level care in both the COVID-19 (1.6 percent) and influenza (4.0 percent) cohorts.