Epidemiological studies, including the Framingham study, has shown that coronary heart diseases present at an earlier age in men than in women [12]. Claassen et al. also has reported that coronary vascular disease in women develops 7 to 10 years later than in men, potentially because of a protective effect of estrogens [11]. Our study could confirm these findings where the mean age of onset of ACS was higher in females than in males showing a gap of about 2 to 3 years in our population.
Men are known to have a higher risk of ACS than women. However, data on potential gender differences regarding the occurrence of ACS have been scarce. A French registry of UA admissions reported71.2% of patients to be men, while in an Australian study, the proportion was 60.2%. In smaller studies, male predominance in patients with UA has ranged from 83.9–56.6%. Another study in Finland found 61.9% of patients to be men, with men having a 2.4-fold overall risk for UA admission in the general adult population compared towomen[13]. The incidence rate of STEMI was also higher in men than in women, which was evident by several previous studies [13–16]. However, 53.7% of UA patients were females in our study population, and only 46.3% of UA patients were males.
In contrast, 75.8% of STEMI patients were males, and 24.2% of STEMI patients were females. Furthermore, concerning male and female populations separately, most of the females had unstable angina (50.5%) and, most of the males had STEMI (38.1%). However, the findings for STEMI go according to the previous studies; for unstable angina, the findings contrast.
The sex difference in occupations was marked with most males with ACS were engaging in skilled occupations, but most females being unemployed. However, this can be attributed to the sex-specific population prevalence of economically active proportion in Sri Lanka, where male shows 65.7%, and females show only 34.3% [17].
In 2008, nearly 1.5 billion individuals were overweight; of these, more than 300 million women and nearly 200 million men were obese, and the world’s average BMI had increased with 0.5 kg/m2 per decade in women and 0.4 kg/m2 in men to an average level of BMI of 24.1 kg/m2 for women and 23.8 kg/m2 for men in 2008[18]. The prevalence of overweight in men and women differs according to the country’s level of development; BMI levels are typically higher in men than women in most high-income countries, whereas the reverse is more common in lower and middle-income countries[18]. The association between BMI and coronary heart disease is broadly identical between men and women, whereas the risk for stroke associated with increments in BMI may be higher in men than in women[1]. Analyses from the Asian-Pacific Cohort Studies Collaboration (APCSC) also demonstrated the approximately equal strength of the association between overweight or obesity and the risk of CHD between men and women in both Asian and Australian populations[19]. In our population, the mean BMI was higher in females (24.95 ± 4.40 kg m− 3) than in males (23.77 ± 3.88 kg m− 3). The prevalence of obesity was higher in females than in males; however, the prevalence of overweight was higher in males than in females.
Our study populations showed a higher mean hip circumference in females (95.6 ± 11.9 cm) than in males (89.3 ± 12.7 cm), though there was no significant difference between the waist circumference. Thus the mean waist-hip ratio was higher in males (0.98 ± 0.07) than in females (0.94 ± 0.10). Despite the widely recognised sex dimorphism in the body fat distribution, there is no evidence that measures of abdominal adiposities, such as waist circumference or waist-hip-ratio have a different relationship with risk for ACS than BMI as a measure of general adiposity, nor that the associations between ACS risk induced by measures of abdominal adiposity are differential between men and women[1]. However, the INTERHEART study has identified waist-hip ratio as a separate risk factor for ACS [11], and also evidence suggests that central adiposity measures, waist circumference, might best predict disease risk at the individual level[18]. In LMICs, studies on women show waist circumference have increased and may contribute to CVD increase[5]. South Asians show a higher rate of ACS at a younger age than those in other countries, very likely due to South Asians having more risk factors at ages < 60years when stratified by age, including higher apolipoprotein B100 /apolipoprotein A-I ratio and higher waist to hip ratio[20].
Diabetes, hypercholesterolaemia, hypertension, smoking and alcohol are well-established risk factors for developing coronary artery disease, presenting differently in men and women[9, 10]. Khan et al. have found a higher proportion of family history of premature coronary artery diseases among females than males in a study done on young patients [21]. However, a study done in Netherland has revealed a low prevalence of family history of coronary artery disease in females (40.2%) than the male (42.1%) with ACS [22]. There was no significant difference in family histories of IHD, diabetes mellitus, stroke or dyslipidaemia in our population. However, female patients showed a higher percentage of family history of hypertension than in males (24.1% vs 17.0%).
The eleven-year Spanish National Health Service trend revealed that among the patients with STEMI and NSTEMI, comorbidities including congestive heart failure, cardio-respiratory failure, valvular or rheumatic heart disease, hypertension, stroke, renal failure, and diabetes Mellitus were more frequent in women[16]. Furthermore, many ACS studies have shown women to have higher incidences of comorbidities at presentation[2, 23, 24], which are consistent with the findings in our study where most of the females were co-morbid with diabetes (37.9%), hypertension (59.8%) and dyslipidaemia (40.3%) than males (25.5%, 39.4%, and 18.1%, respectively).
By 2030, it is estimated that each year approximately 10 million deaths will be due to tobacco use, and the Global Adult Tobacco Survey has shown that in 14 LMICs, 48.6% of men and 11.3% of women were tobaccousers[5]. Smoking remains a significant public health issue in Europe. Although smoking has declined in many European countries, the rate of decline is now slow, and rates remain stable or are increasing in some countries, particularly among women. Women are now smoking nearly as much as men in many European countries, and girls often smoke more than boys[9]. However, while some studies were done among ACS patients state the prevalence of smoking in males is higher than females, other studies state that there is no statistically significant difference, or females having a higher prevalence of smoke than males depending on the sociodemographic conditions [9, 11, 20–23, 25]. According to our study, males showed a significantly higher prevalence of smoking than females, where 42.3% were ex-smokers, and 29.0% were currently smoking while non-the females were ex-smokers or current smokers. The same results were obtained for alcohol intake, where 47.5% of males were currently taking alcohol, and 22.1% had taken alcohol in the past; however, only one female (0.6%) were currently taking alcohol, and none was ex-alcoholics. While moderate alcohol consumption (one or two drinks a day) reduces CVD risk, at high levels of intake, mainly when consumed in episodes of hefty consumption, the risk of CVD is increased[9]. However, alcohol consumption in South Asians is low compared to the other countries, and there is no difference in the prevalence of alcohol consumption between the ACS patients and the general public [20]. However, among Indians, it has been shown a significant association between alcohol consumption and ACS [20]. Alcohol abuse is a risk factor for the occurrence of early ACS, and patients with a combination of alcohol abuse and smoking had an even higher risk of developing very early ACS than those with the two individual risk factors alone[26]. The percentage of alcohol-attributable deaths among men amount to 7.7 % of all global deaths compared to 2.6 % of all deaths among women. Total alcohol per capita consumption in 2010 among male and female drinkers worldwide was 19.4 litres for males and 7.0 litres of pure alcohol for females[27]. The prevalence of alcohol consumption in Sri Lanka is significantly higher in males than in females [4]. Therefore the findings on alcohol consumption from this study can be attributed to the population prevalence of alcohol consumption in Sri Lanka.
Many studies have found that chest pain is the main presenting symptom in ACS, with the prevalence ranging from 88–94% [21, 24, 28]. In addition, chest pain is the most common symptom for men and women regardless of ACS type; however, women are more likely to present without chest pain than men[21]. Another study revealed that men and women presented equally with chest pain; however, jaw pain and nausea were more frequent among women[24]. Younger women are even less likely to present with chest pain [22]. Our study confirmed that chest pain is the predominant symptom presented in 93.4% of the population; nevertheless, there was no statistically significant difference between the Sex. However, right chest pain was primarily present in females than in males and radiation of chest pain to the right arm mainly occurred in males than in females. In addition, the associated symptoms of vomiting and dyspnoea occurred mainly in females (47.7% and 53.1%) than in males (38.4% and 43.2%) but, the other symptoms, such as faintishness, palpitations and sweating, showed no difference with the Sex. Previous studies also have found more symptoms in women with ACS than in men [21, 24].
According to clinical guidelines published by the American College of Cardiology/ American Heart Association, invasive therapy is favourable when the patient presents within 24 hours from the onset of chest pain for NSTE-ACS and within 12 hours from the onset of chest pain for STEMI [7, 8]. Primary percutaneous coronary intervention is recommended to perform if the patient presents within 2 hours of the onset of symptoms [8]. The average delay in presentation to the health care facility from the onset of symptoms in ACS patients has been between 1.5 to 2.5 hours, as revealed by several studies [8, 28, 29]. Thus, patients with STEMI do not seek medical care for approximately 1.5 to 2 hours after symptom onset, and little change in this interval has occurred over the past ten years[8]. However, our study revealed that the average delay was 5:52, 5:51 and 4:26 for unstable angina, NTEMI and STEMI, respectively, showing considerably higher values than the previous studies. The main reason for this delay was not suspecting an IHD present in 60% of patients regardless of Sex. Three-wheeler was the primary mode of transport (59.0%) to the hospital, and only 7.0% was delayed due to the unavailability of a transport facility. Although the three-wheeler has not been a safe option to transport an emergency patient[30], it has been the widely available transport facility in Sri Lanka, as evident by this study. In those who had STEMI, the delay in the presentation was more in females (6:04) than males (3:55), confirming the findings from the previous studies that women show a more significant delay in presentation than men [2, 8, 14, 22, 29]. One reason for this may be that women show more atypical symptoms of ACS than men [24, 29].
Menopause signals the transition from reproductive to non-reproductive life and is associated with several biological changes to the endocrine system relevant to cardiovascular health. Age at menopause logically translates to the interval of estrogen and androgen exposure and is associated with a modest risk difference in CVD[1]. However, Atsma et al.’s meta-analysis has found no convincing relationship between postmenopausal status and cardiovascular disease, though there is a modest effect of early menopause on cardiovascular disease[31]. Nevertheless, the mean age of onset of ACS in females is 4 to 8 years later than males, which may be attributed to the protective effect of oestrogen in younger females [2, 22, 25, 26]. Our findings tally with the previous studies where the mean age of onset of chest pain (62.2 years) was significantly higher than the males (59.8 years). At the same time, in females, the mean age of onset for unstable angina (60.5 years) was significantly lower than the mean age of onset for NTEMI (63.8 years) and STEMI (64.0 years), indicating that the severity of ACS increases with age. The mean age of menopause does not show any statistically significant difference within the spectrum of ACS. Since only 130 (16.5%) female patients had responded regarding the usage of contraceptives, the effect of contraceptives on the occurrence of ACS was inconclusive.