Strengths:
- The study included a large sample size, which improves the
generalizability of the findings.
- The study was performed during both influenza and non-influenza
seasons which allows for a comparison of the prevalence and impact of
respiratory illnesses among patients with AMI in different seasons.
- The study used a standardized protocol to identify and recruit cases
with AMI, reducing the potential for misclassification bias.
- The case definition for recent acute respiratory illness used in the
study is clearly defined and based on widely recognized respiratory
symptoms increaseing the sensitivity of the exposure variable and the
use of qRT-PCR testing to confirm influenza is a reliable method.
- The study conducted multivariate regression analysis to control for
potential confounders when investigating the relationship between
recent respiratory illness and severity of AMI .Limitations:
- The study’s cross-sectional design, without a control group, limits
its ability to infer potential associations between recent respiratory
illness, influenza, and the onset of acute myocardial infarction.
- The study relied on self-reported respiratory symptoms to identify
patients with history of recent respiratory illness , which may be
subject to recall bias or misreporting.
- The study only collected data from a single study hospital , which may
not be representative of the broader population of Bangladesh.
-
- The study was underpowered to detect statistically significant
differences in some sub-group analyses, such as the association
between recent respiratory illness and STEMI during influenza seasons.What is already known on this topic?
- Influenza and recent acute respiratory illnesses may precipitate
adverse cardiovascular events like acute myocardial infarction. There
is limited data on prevalence of recent respiratory illness and
laboratory-confirmed influenza from low-income countries like
Bangladesh in spite of having high burden of both acute respiratory
illnesses and cardiovascular diseases. There is also scarcity of data
on the relationship between recent respiratory illness and influenza
with severity of myocardial infarction.What this study adds?
- The current study provides an estimate of the prevalence of recent
acute respiratory illnesses and laboratory-confirmed influenza
preceding the onset of acute myocardial infarction among Bangladeshi
population, unveiling some insights from low-income settings.
Additionally, the study generated some data, in low-income settings,
on the relationship between recent respiratory illness and influenza
with severity of myocardial infarction across different study seasons.How this study might affect research, practice or policy?
- The findings from the current study underscore the need for further
investigations into the role of influenza and other acute respiratory
illnesses in the onset of acute myocardial infarction in Bangladesh
and other low-income settings. The findings highlight the importance
of heightened awareness among vulnerable patients as well as
healthcare workers regarding the cardiovascular risk of seasonal
outbreaks of influenza and other acute respiratory illness in
Bangladesh. This may lead to improved timeliness of early
interventions and better patient outcomes. Lastly, the potential
benefits of infection prevention and control measures and influenza
vaccination programs against the incidence of acute cardiovascular
events in Bangladesh deserve further exploration.INTRODUCTION:
Influenza-associated
acute respiratory illness (ARI) accounts for millions of severe cases
and more than half a million deaths worldwide every
year(1, 2).
Adults with comorbid illness and those aged more than 65 years are at
higher risk of severe influenza
outcomes(1) such as intensive care unit
admissions (3). The 2009 pandemic H1N1
influenza is thought to have contributed to more than 80,000 additional
cardiovascular deaths globally indicating an unrecognized burden of
severe influenza(4). Furthermore, adverse
cardiovascular incidents such as acute myocardial infarction (AMI) and
stroke contribute to almost one-third of all deaths worldwide, and the
majority of the global burden of AMI is currently observed in low- and
middle-income countries, such as Bangladesh, where it is on a yearly
rise (5-7).
An AMI may be precipitated from a vulnerable atherosclerotic plaque
rupture after short term exposure of certain triggering factors such as
acute respiratory infection(8). Increase
in incidence of acute cardiovascular events such as AMI and stroke
during winter months has been attributed to ARI, along with other
determinants over the past years(9).
Temporal variations in acute cardiovascular events were reported as
early as 1937 (10) and several
time-series analyses showed correlations of seasonal peaks of
influenza-associated mortality with cardiovascular deaths
(11-15).
Meta-analysis of multiple
case-control studies revealed that AMI cases were associated with
greater incidence rates of recent acute respiratory illness,
influenza-like illness, and laboratory-confirmed influenza compared to
control groups (pooled OR 2.01; 95% CI 1.47 to 2.76)
(16), which suggests that recent ARI and
influenza may significantly contribute to the occurrence of AMI events.
Furthermore, self-controlled
case-series investigations have reported a heightened risk of AMI in the
immediate aftermath of acute respiratory illness and
laboratory-confirmed influenza (17-20).
Influenza and ARI have also been known to exacerbate myocardial injury,
as indicated by troponin levels (21).
Although influenza-associated AMI may go unnoticed, it can be prevented
through influenza-specific preventive measures, such as influenza
vaccination, which has been proven effective in various large-scale
randomized controlled trials (RCTs) (22)
as well as several smaller RCTs (23-25).
Like other low- to middle-income
countries, an inadequately investigated double burden of communicable
illnesses such as ARIs and non-communicable diseases such as adverse
acute cardiovascular events like AMI prevails in Bangladesh
(26). National surveillance data confirms
annual seasonal influenza prevalent among hospitalized patients
throughout Bangladesh with unimodal peak during rainy season and may be
associated with deaths among older adults and elderly
(27, 28).
Despite the existing burden of incidences of AMI, as well as the
concomitant evidence of circulating influenza among the population there
is lack of data and awareness on the prevalence of influenza as well as
recent ARI exclusively among AMI patients in Bangladesh, which incited
the current investigation. Therefore, the primary research question was
about the prevalence of recent ARI and laboratory evidence of influenza
among patients with AMI in Bangladesh. This information is crucial for
understanding the extent of the impact of these illnesses on the
cardiovascular health of the population and for developing targeted
interventions. To address the gap, the
current exploratory study aimed
to estimate the prevalence of recent respiratory illness and
laboratory-confirmed influenza among patients hospitalized with AMI. A
secondary aim was to explore the association of recent respiratory
illness with severity of infarction. As an initiative, we opted for a
cross-sectional design without a control group for its time efficiency,
simplicity and ability to include a larger population.