Acute coronary syndrome (ACS) in young adults is a rare entity, but it does occur. It is important to assess the clinical features, risk factors, and outcomes, which may be due to the primary disease or may be secondary as complications, so that measures to prevent further episodes of ACS can be undertaken.
In this study, the cutoff point that we used to define young patients was 45 years. It was determined based on the results of similar studies in Thailand, Singapore, Israel, and California.13,14 Other studies have defined the young age to be under 40 years, including studies from Japan, Poland, Germany, Australia, New Zealand, and the USA.14
Our findings are as follows: First, 109 patients who had ACS were younger than 45 years with a mean age of 38 ± 7. Second, regarding risk factors, as expected, older patients had a higher frequency of hypertension, diabetes, and a history of CAD. On the other hand, they had less frequent history of smoking and family history of ACS, which were higher among younger patients. Furthermore, a recent retrospective cohort study of two academic institutions suggests an increased likelihood of encountering ACS with a family history of hypercholesterolemia.15
In previous studies, the most crucial risk factor for the development of ACS in young adults was smoking. The literature reports that 82% of young patients who suffered from ACS were smokers. An interesting finding was reported by Huang and colleagues who found that the rate of smoking in patients aged ≤ 35 years and who suffered from MI was significantly higher than in patients > 65 years of age who suffered from the same condition.
All of these findings suggest that a history of smoking and family history of cardiovascular disease are risk factors in young patients with ACS (Fig. 1), which is consistent with the findings of other studies.16,17,18 A study in Thailand reached the same conclusion, where it was discovered that the most common risk factor of ACS in patients aged < 45 years of age was smoking.13 A different study found that patients whose parents developed cardiovascular disease of early onset had an increased risk of cardiovascular disease.19
Smoking is a major risk factor for ACS in young patients for multiple reasons. Both quantity and duration of smoking quicken the development of atherogenic cardiovascular disease.20,21
Furthermore, smoking also alters the defensive response of the immune system against vascular damage, which is characterized by an increase in oxidative influence on lipid peroxidation, endothelial cell dysfunction, and generation of foam cells in the tunica media.21,22 It also leads to increased platelet aggregation, disrupts the metabolic activities of lipoproteins, and tends to reduce HDL cholesterol.21,22 Cigarette smoking is linked to increased levels of inflammatory markers. During the acute phase of the inflammatory process, C-reactive protein is elevated, white blood cells and fibrinogen are increased, and serum albumin is decreased.20,21,22 Smoking can also increase myocardial load due to stimulation by catecholamines and reduce consumption of O2 due to inhalation of carbon monoxide, which may cause tachycardia, vasoconstriction of blood vessels, and which may modify the permeability of the vessel wall.21,22
Primary and secondary prevention specifically are important in this subset of patients. In addition, one study has shown that diabetes mellitus was more prevalent in younger adults. Acute coronary syndrome is clinically similar in both young patients and the elderly, and this has been emphasized by several authors.9,23−26 However, in our study, we found that palpitations occurred more frequently in younger adults.
In addition, some laboratory parameters including creatinine, and BUN, were higher in older patients, but HGB, LDL, and cholesterol levels were higher among younger patients. This result was similar to those of previous studies.
In terms of length of stay, other studies have shown that older patients with ACS had longer hospital stays.27, 28 on the other hand, in our study, the length of stay was not significantly different between the two age groups. In our study, in-hospital mortality was 7.4% among older patients and 0.9% among younger patients. Our findings align with those of a recent cohort of Junjie Yang et al., which have demonstrated equity among younger and older adults in terms of short- and long-term outcomes.29
Potential limitations of our study include the fact that our selected design was retrospective. However, our sample size was reasonably large (652 cases), which in our opinion reduced information bias and therefore strengthened the results.