Although most prevalent in elderly, myocardial infarction (MI) also affects younger adults. We sought to investigate baseline characteristics in young patients (<55 years) with MI using the National Inpatient Sample (NIS) database between 2004 and 2015. Multivariable logistic regression models were used to assess factors associated with acute myocardial infarction (AMI) in young patients. After multivariable analyses adjusted for age, sex, race, family history of atherosclerosis, body mass index (BMI), diabetes, hypertension, hyperlipidemia, chronic kidney disease, and current cigarette smoking; novel risk factors such as human immunodeficiency virus (HIV), systemic lupus erythematosus (SLE), and obstructive sleep apnea (OSA) were associated with a higher risk of developing an AMI in the young (adjusted OR for HIV 4.06; 95 CI 3.48-4.71, p < 0.001), (adjusted OR for SLE 2.12; 95 CI 1.89-2.39, p 0.04), and (adjusted OR for OSA 1.16; 95 CI 1.12-1.20, p < 0.001), respectively. Rheumatoid arthritis was associated with a lower risk of AMI (adjusted OR 0.83; 95 CI 0.76-0.89, p < 0.001). After multivariable analyses, cigarette smoking (adjusted OR 1.98; 95 CI 1.95-2.02, p < 0.001), obesity (adjusted OR 1.37; 95 CI 1.33-1.41, p = 0.003), hyperlipidemia (adjusted OR 1.07; 95 CI 1.04-1.08, p < 0.001) and a family history of CAD (adjusted OR 1.35; 95 CI 1.3-1.4, p < 0.001) were also associated with a higher risk of developing an AMI in the young. In conclusion, young patients with AMI have both traditional risk factors and non-traditional risk factors. In addition to traditional risk factors, close attention should be paid to emerging risk factors such as SLE, HIV and OSA.