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ORIGINAL ARTICLE
Year : 2023 | Volume
: 24
| Issue : 4 | Page : 171-178
Smoking in acute myocardial infarction patients: Observations from a registry heart hospital, Qatar
Hajar Ahmed Hajar Albinali1, Rajvir Singh1, Omnia Tajelsir Abdalla Osman1, Abdul Rahman Al Arabi1, Betsy Varughese2, Awad Al Qahtani1, Nidal Asaad1, Jassim Al Suwaidi1
1 Department of Adult Cardiology, Heart Hospital, Hamad Medical Corporation, Doha, Qatar
2 Department of Gastroenterology-Medicine, Hamad Medical Corporation, Doha, Qatar
Correspondence Address:
Dr. Hajar Ahmed Hajar Albinali
Department of Adult Cardiology, Heart Hospital, Hamad Medical Corporation, Post Box: 3050, Doha
Qatar
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/heartviews.heartviews_26_23
Abstract
Introduction: Studies from the US and Europe showed a decline in smoking among patients with acute myocardial infarction (AMI), but limited data are available from the Middle East. In this study, we describe the temporal trend in the prevalence, associated risk factors, and outcomes of smoking among patients with AMI in Qatar.
Materials and Methods: A total of 27,648 AMI patients were analyzed from the cardiology registry at Heart Hospital, Doha, Qatar. This spans from January 1991 to May 2022.
Results: Of the total, 13,562 patients (49.1%, 95% confidence interval [CI]: 48%–50%) were smokers, with a clear majority of males (98.5%). Smoking habit was found to decrease in AMI patients with increasing age (age 51–60 years, adjusted odds ratio [OR]: 0.71, 95% CI: 0.67–0.76, P = 0.001, and age ≥61 years, adjusted OR: 0.45, 95% CI: 0.42–0.48, P = 0.001, in comparison to age ≤50 years). Smoking was associated with a lower risk of inhospital mortality (adjusted OR: 0.61, 95% CI: 0.54–0.70, P = 0.001), but triglyceride, obesity, and old myocardial infarction risk factors were associated with a higher risk. A decreasing trend in current smoking habits in each quantile of the 1996–2000 year (adjusted OR: 0.82, 95% CI: 0.71–0.93, P = 0.001), 2001–2005 year (adjusted OR: 0.70, 95% CI: 0.62–0.80, P = 0.001), 2006–2010 year (adjusted OR: 0.75, 95% CI: 0.67–0.84, P = 0.001), 2011–2015 year (adjusted OR: 0.48, 95% CI: 0.42–0.54, P = 0.001), 2016–2020 year (adjusted OR: 0.48, 95% CI: 0.43–0.54, P = 0.001), and ≥2021 year (adjusted OR: 0.46, 95% CI: 0.40–0.53, P = 0.001) was observed in comparison to the quantile 1991–1995 year. Similar results were also observed in the young population (age ≤50 years) including the non-Qataris, who had 25% more smokers in comparison to Qatari nationals.
Conclusion: Smoking trended down significantly; however, it remained prevalent in 50% of patients among AMI patients. Smokers were younger, with fewer traditional risk factors, and had lower inhospital mortality.
Keywords: Acute myocardial infarction, cardiology registry, inhospital mortality, Qatari nationals, smoking habit
Introduction 
The most common cause of morbidity and mortality in the world is acute myocardial infarction (AMI) with varying incidences in countries and ethnicities.[1],[2] AMI accounts for 10%–25% of deaths in industrialized countries, and it is on the rise in emerging nations as well. Half of the patients die from the illness, and those who survive have impaired heart function.[3] An AMI occurs when blood flow to a part of the heart is cut off. This causes some heart cells to die. A fragile atherosclerotic plaque, a mass of lipids and white blood cells, often ruptures and blocks or impedes the coronary arteries. It is associated with multiple risk factors, including smoking, diabetes, hypertension (HTN), obesity, periodontal disease, stress, physical activity, and dyslipidemia. Among them, smoking is the most modifiable risk factor.[4],[5]
Previous studies have shown that the life expectancy of smokers is at least a decade shorter when compared to those who have never smoked.[6] In healthy patients, it causes early ST-elevation myocardial infarction (MI). Smoking-related illnesses claim more lives among those under the age of 70 years than all other causes of death.[7] Young people were more susceptible to the dangers of smoking for nonfatal AMI.[7] Furthermore, the impact of smoking was significantly higher in women than men in causing AMI.[8]
Contrarily, many clinical studies have documented that smokers might have a better prognosis following AMI events when compared to nonsmokers.[9],[10],[11],[12],[13],[14],[15] These paradoxical results have, however, raised questions, and it has been found that smoking does not contribute to a positive outcome; rather, it is likely to be confused by several baseline factors that deteriorate outcomes and cause smoking cessation.[15] In many studies, age was not adjusted despite being one of the risk factors for AMI. Such studies showed a better prognosis following AMI events in smokers.[15] The observed protective effect of smoking in such studies is presumably due to the younger age of the smokers rather than the smoking itself.[16]
Many factors associated with AMI mediate their risk via other factors. Furthermore, most of the risk factors prevalent in AMI patients are modifiable. Awareness of smoking risks, especially in the young population, is undoubtedly a vital public health message to reduce the incidence and mortality of AMI.
In a meta-analysis of 12 studies, smokers who quit smoking had a 0.54 times lower overall mortality than those who continued to smoke.[15] However, the association of smoking with the outcomes of AMI patients remains controversial and has implications for public health. Furthermore, there is a scarcity of information available on the prevalence and risks associated with smoking in AMI patients in Qatar. Hence, we analyzed the data of AMI patients from a cardiology registry of more than three decades to understand the prevalence and risks associated with smoking in such patients.
Materials and Methods The European Society of Cardiology and the American College of Cardiology Consensus Group guidelines have been used for the diagnosis of AMI. Cardiology registry data from Heart Hospital, a tertiary hospital in Qatar, have been used for the analysis spanning January 1991–May 2022. Cigarettes, water pipes, cigars, and chewing tobacco are included in current smoking. Details about the registry have been published previously.[17] In brief, this is a retrospective study and involves the analysis of an anonymous dataset. The Institutional Review Board granted a waiver of informed consent to conduct the study (MRC#11355/11). A predefined coded record form (CRF) was used at the time of the patient's hospital discharge, and recorded data were checked and validated. From January 1991 to April 2022, 27,648 patients aged 18 years and older were diagnosed with AMI.
Continuous variables were presented in mean and standard deviation or interquartile range as appropriate whereas frequency with percentages was calculated for categorical variables. Data were divided into two groups (nonsmokers vs. smokers) and Student's t-tests or Wilcoxon rank sum tests were performed to compare continuous variables as appropriate. Chi-square tests were used to determine the association of categorical variables. Multivariate logistic regression was applied to determine associated risk factors for smoking in acute MI cases. Because of the collinearity between body mass index (BMI) and obesity, only obesity was included in the multivariable analysis. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were presented. The statistically significant level was determined by a two-tailed (P ≤ 0.05). SPSS 28.0 Statistical package, IBM Corp. Release 2021, IBM SPSS statistics for windows, Version 28.0, Armonk, NY, USA: IBM Corporation was used for the analysis.
Results Among 27,648 acute MI cases, 13562 (49.1%) were smokers, with 98.5% of males and 1.5% of females. Smokers were 7 years younger than nonsmokers (51.6 ± 10.7 vs. 58.3 ± 12.8, P = 0.001). Non-Qatari were more likely to smoke than Qatari (84.9% vs. 15.1%, P = 0.001). Triglyceride (TG) levels and family history (FH) were more prevalent in smokers than the nonsmokers (5.8% vs. 4.6%, P = 0.001, and 3.6% vs. 2.5%, P = 0.001, respectively), whereas BMI ≥30 (22.7% vs. 19.8%, P = 0.001), inhospital mortality (7.5% vs. 3.3%, P = 0.001), HTN (51.5% vs. 34.9%, P = 0.001), cholesterol (15.5% vs. 12.1, P = 0.001), obesity (4.7% vs. 3.6%, P = 0.001), chronic renal failure (7.1% vs. 3.1%, P = 0.001), and old MI (15.2% vs. 12.9%) were more prevalent in nonsmokers than the smokers in acute MI patients. There was a decreasing trend observed in smoking habits in each quantile of the admission year [Table 1].
Table 1: Comparison of risk factors between smokers and nonsmokers in acute myocardial infarction cases[Table 2] describes percentages of admission medication, complications, and procedures between smokers and nonsmokers. Acetylsalicylic acid and beta-blockers were more prevalent in smokers than nonsmokers, but in contrast, angiotensin-converting enzyme and angiotensin receptor blockers, Ca-blocker, clopidogrel, warfarin, heparin and low-molecular-weight heparin, and inotropes were statistically more prevalent in nonsmokers. Regarding complications, the frequency of atrial fibrillation, arrest, and CHF was more in the nonsmokers' group. Procedures such as right/left heart, percutaneous transluminal coronary angioplasty, and percutaneous coronary intervention were more in the smoker group.
Table 2: Comparison of admission medication, complications, and procedures between smokers and nonsmokers in acute myocardial infarction cases[Table 3] shows the distribution of laboratory parameters.
Table 3: Comparison of laboratory parameters between smokers and nonsmokers in acute myocardial infarction cases[Table 4] presents the distribution of the young (≤50 years of age) population of AMI patients. Of the total 10,631, 6634 (62.4%) were smokers and almost all of them were males 6585 (99.3%).
Table 4: Comparison of risk factors between smokers and nonsmokers in young patients (age ≤50 years) of acute myocardial infarction casesIn-hospital mortality (3.2%), diabetes mellitus (35.0%), HTN (31.6%), cholesterol (13.4%), chronic renal failure (2.1%), and old MI (7.4%) were more prevalent in nonsmokers. Qataris were fewer smokers in comparison to non-Qatari nationals. There was also a decreasing trend of smoking habits in each quantile of the admission year starting from the first quantile 1991–1995 to ≥2021.
Data were also represented in graphs. [Figure 1] shows the mean age of smokers and nonsmokers in AMI patients, whereas [Figure 2] describes the distribution of smokers and nonsmokers according to the age categories suggesting that as age increased, the smoking decreased. [Figure 3] describes the mean age at inhospital mortality in AMI patients for smokers and nonsmokers, whereas [Figure 4] demonstrates the distribution of inhospital mortality in percentage for smokers and nonsmokers in AMI patients according to year quantiles.
Figure 1: Mean age of acute myocardial infarction patients according to smokers versus nonsmokers
Figure 2: Distribution of age between smokers versus nonsmokers in acute myocardial infarction patients
Figure 3: Average age in years at inhospital mortality in acute myocardial infarction patients
Figure 4: Distribution of deaths in acute myocardial infarction patients according to smokers versus nonsmokers[Table 5] describes the multivariate analysis for associated factors of smokers in AMI cases. Smoking habit was found to decrease in AMI patients as age increased (age 51–60 years, adjusted OR: 0.71, 95% CI: 0.67–0.76, P = 0.001, and age ≥61 years, adjusted OR: 0.45, 95% CI: 0.42–0.48, P = 0.001, in comparison to age ≤50 years). Inhospital mortality was found to be lower among smokers (adjusted OR: 0.61, 95% CI: 0.54–0.70, P = 0.001), but factors TG, obesity, and old MI were found to be associated with smoking habit.
Table 5: Associated factors for smokers in acute myocardial infarction cases using multivariate analysis casesMultivariate regression also showed that the decreasing trend in smoking habits in each quantile 1996–2000 year (adjusted OR: 0.82, 95% CI: 0.71–0.93, P = 0.001), 2001–2005 year (adjusted OR: 0.70, 95% CI: 0.62–0.80, P = 0.001), 2006–2010 year (adjusted OR: 0.75, 95% CI: 0.67–0.84, P = 0.001), 2011–2015 year (adjusted OR: 0.48, 95% CI: 0.42–0.54, P = 0.001), 2016–2020 year (adjusted OR: 0.48, 95% CI: 0.43–0.54, P = 0.001), and ≥2021 year (adjusted OR: 0.46, 95% CI: 0.40–0.53, P = 0.001) was observed in comparison to the year 1991–1995 quantile.
A similar trend toward decreasing smoking habits was found in the young populations (age ≤50 years) after adjusting for other significant associated risk factors for smoking. Non-Qatari nationals smoked 25% more than Qataris. TG, FH, obesity, and old MI were also associated with smoking habits [Table 6].
Table 6: Associated factors for smoking in acute myocardial infarction young population (age ≤50 years) Discussion We used data from more than 30 years of the cardiology registry at Heart Hospital, HMC, Qatar. Nearly half of the AMI patients were smokers at the time of index hospitalization and were an average of 7 years younger than nonsmokers. A reduction was observed in smoking habits as age increased after adjusting other important risk factors of AMI patients in multivariate regression. The same trend was seen in the young population. TG levels and FH were associated with smokers, whereas other modifiable risk factors such as HTN, cholesterol, obesity, chronic renal failure, and previous MI were more prevalent in nonsmokers.
A previous study from Italy showed that there were 45.6% of smokers in AMI patients, which were 2.2 times more in number when compared to not AMI patients.[18] About 50% of patients with AMI were smokers in another study. In addition, the study also suggested that current smoking is associated with lower life expectancy and a significant loss of life years after AMI.[6] Our study also showed 49.1% of smokers in AMI patients.
Although smoking has been prohibited in public places such as schools, education centers, and hospitals, smoking cigarettes and traditional hookahs is very common in Qatar. The 1991–1995 quantile indicated that 76% of young adults smoked, whereas the number of young adults who smoked had fallen to 50.9% by 2021.
There was a decreasing trend in smoking habits in the total sample population and among young people. The prevalence of current smoking habits in the study is more than 50% in the young population. There were 25% more smokers among young expatriates compared to Qatari nationals. Our results also confirm the existence of a smoker's pseudo paradox[19] due to the lack of follow-up data and reports of decreased mortality in smokers.
The mean age of both the full cohort and the subset of patients classified as smokers at the time of MI was at least 5 years younger[20],[21],[22],[23] and more than 10 years younger[14],[24],[25],[26],[27],[28],[29],[30],[31],[32] when compared with the cohorts of other studies. Furthermore, it reported that the reduced life expectancy of smokers was approximately 7 years less than that of nonsmokers.[33],[34] In our study, we also found that smokers were 7 years younger at the time of index hospitalization than nonsmokers.
We also found that as age increased, smokers also decreased, possibly due to physicians' advocacy of smoking cessation, the national awareness campaign, and the availability of smoking cessation services across the nation. The previous studies also advocated a higher risk of AMI in women smokers than in men, where the difference was much greater for heavy and long-term smokers.[35],[36],[37],[38],[39],[40]
Multiple cardiac risk actors were more prevalent in AMI patients, particularly among black women. These findings highlight the need to modify risk factors in these high-risk groups.[41] In contrast, our study has a smaller number of female smokers in comparison to male smokers in the overall and young population. We found 14–15 times more male smokers than female smokers. The more male smokers may be due to the cultural taboos in the country, as well as the most male expatriates coming without families to earn a living.
The variations in the outcomes of care in AMI patients across hospitals may be due to multiple factors, such as organizational culture, hospital structure, and processes of care.[42]
Our study also showed a decreasing trend of inhospital mortality in the overall and young population. Smoking is associated with cardiovascular disease (CVD) in young patients. It is, therefore, essential to avoid all forms of smoking and chewing tobacco to prevent the development of CVD. It is also well known that quitting smoking improves blood circulation and glucose levels and reduces bad cholesterol, ultimately reducing many preventive ailments and conditions, including CVDs.
Conclusion Nearly 50% of AMI patients were smokers in our study and were approximately a decade younger than nonsmokers. Furthermore, most cardiac risk factors prevalent in AMI patients are modifiable. Hence, awareness of smoking risks, especially in the young population, is undoubtedly a vital public health message to reduce the incidence and mortality of AMI in the community.
Limitations
Our study may have all the limitations of a retrospective study, even though there are huge data for analysis. The results on smoking between males and females could not be compared as most of the population are male immigrants in the country. Although a decreasing trend in smoking is apparent, there are no data on the duration of smoking and quitting smoking to quantify the real difference in estimates between smokers and nonsmokers. Additionally, the study does not provide long-term follow-up information about smoking habits after the age of AMI to demystify the smoker's paradox.
Data sharing statement
Registry data are available at the Cardiology Research Center, Heart Hospital, Hamad Medical Corporation (HMC).
Ethical approval
The Institutional Review Board granted a waiver of informed consent to conduct the retrospective study (MRC#11355/11).
Acknowledgment
Heart Hospital staff are continually assisting with data collection and reviewing registry records.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References 
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