Relationship between seasonal influenza rates and hospitalization and mortality rates due to acute cardiovascular diseases in a Spanish region

Abstract

Introduction and objective

Influenza virus infection can contribute to cardiovascular morbidity and mortality. The purpose of this study is to confirm if the increase in seasonal influenza rates is associated with a growth in hospitalisation and mortality rates for acute cardiovascular diseases (ACVD).

Methods

Retrospective cohort study of hospital discharges due to ACVD (myocardial infarction, unstable angina, heart failure and ischemic stroke) in the Castilla y León (Spain) hospital system between 2001 and 2015. Hospitalisation and hospital mortality rates due to ACVD, and influenza rates in Castilla y León between 2001 and 2015 were studied. To calculate hospitalisation and mortality rates, the hospital discharges database was used; for influenza rates, the weekly reports of the Sentinel System for the surveillance of influenza in Spain (Carlos III Health Institute) were used. A statistical analysis of linear and multivariate logistic regressions was performed.

Results

239,586 ACVD (myocardial infarction: 55,004; unstable angina: 15,406; heart failure: 11,1647; ischemic stroke: 57,529) were studied. Increasing rates of influenza were associated with increased mortality due to ACVD and all the diseases studied, except unstable angina. A linear correlation was observed between influenza rates and hospitalisation (r² = 0.03; p = 0.02) and mortality (r² = 0.14; p < 0.001) rates by ACVD. Virtually all influenza rates were associated, as independent variables, to an increase in mortality due to ACVD, being higher in rates > 139/100,000 inhabitants (OR: 1.25; p < 0.001).

Conclusions

The rates of hospitalisation and in-hospital mortality due to ACVD in the period 2001–2015 increased in relation to infection rates due to the influenza virus.

Resumen

Introducción y objetivo

La infección por virus de la gripe puede contribuir a la morbimortalidad cardiovascular. El objetivo de este estudio es analizar si el incremento en las tasas de gripe estacional se asocia a un crecimiento en las tasas de hospitalización y mortalidad hospitalaria por enfermedades cardiovasculares agudas (ECVA).

Métodos

Estudio de cohortes retrospectivo sobre altas hospitalarias por ECVA (infarto de miocardio, angina inestable, insuficiencia cardiaca, accidente cerebrovascular isquémico) del sistema hospitalario de Castilla y León durante el periodo 2001-2015. Se analizaron tasas de hospitalización y mortalidad hospitalaria, y tasas de gripe en Castilla y León. Para calcular las tasas de hospitalización y mortalidad se empleó el Conjunto Mínimo Básico de Datos (CMBD); para las tasas de gripe, los informes semanales del Sistema Centinela de Vigilancia de la Gripe en España (Instituto de Salud Carlos III). Se realizó análisis estadístico de regresión lineal y multivariante de regresión logística.

Resultados

Se estudiaron 239.586 ECVA (infarto, 55.004; angina inestable, 15.406; insuficiencia cardiaca, 11.1647; accidente cerebrovascular, 57.529). Tasas de gripe ascendentes se ajustaron a mortalidad creciente por todas las enfermedades, salvo angina inestable. Se observó una correlación lineal entre tasas de gripe y de hospitalización (r² = 0,03; p = 0,02) y mortalidad (r² = 0,14; p < 0,001) por ECVA. Las tasas de gripe se asociaron, como variables independientes, a un aumento de la mortalidad por ECVA, siendo mayor en tasas > 139 casos/100.000 habitantes (OR: 1,25; p < 0,001).

Conclusiones

Las tasas de hospitalización y mortalidad hospitalaria por ECVA en el periodo estudiado aumentaron en relación con las tasas de infección por el virus de la gripe.