Risk Factors for Heart Attack
The major risk factors for myocardial infarction are smoking, abnormal lipid levels (elevated ApoB/ApoA1 ratio), hypertension, diabetes mellitus, abdominal obesity, psychosocial stress, lack of daily fruit and vegetable consumption, physical inactivity, and family history of premature coronary artery disease—collectively accounting for over 90% of heart attack risk worldwide. 1
Traditional Cardiovascular Risk Factors
The most well-established risk factors for myocardial infarction include:
Non-Modifiable Risk Factors
- Age: Risk increases significantly after age 55 in men and age 65 in women 2
- Male sex: Men have approximately 2.4 times higher risk of premature MI compared to women 3
- Family history of premature CAD: Confers a 2.7-fold increased risk overall 3, with risk as high as 10.9-fold in some populations 4. The younger the family member at diagnosis, the stronger the familial risk—brothers of patients diagnosed before age 46 have 11.4 times greater risk compared to controls 5
Major Modifiable Risk Factors
Smoking: Current smoking carries the highest modifiable risk with an odds ratio of 4.34 for premature MI 3 and 2.87 in the global INTERHEART study, accounting for 35.7% of population-attributable risk 1. Smoking is particularly powerful as a predictor of sudden cardiac death 6
Abnormal lipid profile: Elevated ApoB/ApoA1 ratio shows an odds ratio of 3.25 and accounts for 49.2% of MI risk 1. Dyslipidemia carries a 2.94-fold increased risk for premature MI 3. Total cholesterol >200 mg/dL, triglycerides >150 mg/dL, and HDL <60 mg/dL each confer 2- to 3-fold higher risk 3
Hypertension: Associated with odds ratios ranging from 1.91 to 3.1 for MI 1, 4, accounting for 17.9% of population-attributable risk 1. Hypertension plays a disproportionate role in sudden cardiac death risk, particularly through development of left ventricular hypertrophy 2
Diabetes mellitus: Confers a 2.37-fold increased risk in the general population 1 and 3.54-fold risk for premature MI 3, with 9.9% population-attributable risk 1
Abdominal obesity: Measured by waist-to-hip ratio, the highest tertile carries 1.62-fold risk compared to lowest tertile, accounting for 20.1% of MI risk 1. Body mass index ≥25 kg/m² is associated with 1.46-fold increased risk 3
Lifestyle and Psychosocial Factors
Psychosocial stress: Type A personality and chronic stress confer a 2.67-fold increased risk, accounting for 32.5% of population-attributable risk 1, 7
Physical inactivity: Sedentary lifestyle increases risk with an odds ratio of 0.86 for those who are active (12.2% population-attributable risk for inactivity) 1
Diet: Lack of daily fruit and vegetable consumption accounts for 13.7% of MI risk 1
Alcohol: Regular moderate consumption shows a protective effect (OR 0.91), though heavy consumption increases risk 1
Risk Factor Clustering and Synergy
Multiple risk factors operate multiplicatively rather than additively 8, 6. In studies of young MI patients, 94% had three or more risk factors present simultaneously 7. The combination of hypertension and hypercholesterolemia creates particularly elevated risk 8.
Age-Specific Considerations
For patients presenting with suspected acute coronary syndrome without known CAD, age is the dominant predictor: males >55 years or females >65 years carry high risk that outweighs all other historical factors, including chest pain characteristics 2.
Clinical Implications
Traditional risk factors like hypertension and smoking are only weakly predictive of acute ischemia at initial presentation, but they strongly predict outcomes once ACS is established 8, 6. This means risk factors should not determine whether to admit or treat for suspected MI—that decision relies on symptoms, ECG findings, and cardiac biomarkers—but they have critical prognostic and therapeutic implications after diagnosis 8.
Common Pitfalls
- Do not dismiss "borderline" risk factor levels in patients with active ischemia; the presence of ischemia itself makes the patient high-risk regardless of absolute numbers 8
- Recognize that coronary disease is commonly asymptomatic or unrecognized in the community, so individuals with unrecognized CAD may only be identified through systematic risk factor screening 2
- In young patients presenting with chest pain, always suspect CAD if they are male smokers or female diabetics, as these are the strongest risk factors in younger populations 7