In the U.S., the average age for a first heart attack is 65 for men and 72 for women — but the risk for heart disease starts building years earlier.

One study suggests that the risk for serious heart problems starts with LDL cholesterol levels as low as 100 in people under age 40. Another study recently found that your cardiovascular health, even as young as age 36, can predict your risk for premature brain aging.

That research published in The Lancet Healthy Longevity found that you end up with a brain age that's older than your actual years if you're hard on your cardiovascular system when you're young.

And a prematurely older brain means you'll do worse on cognitive tests and experience increased brain shrinkage, a potential clinical marker of your risk of serious brain-related maladies.

Are you in your 20s, 30s, or 40s and sedentary, overweight, contending with a hyped-up stress response and/or poor sleep? If worrying about your heart health isn't enough to get you to change your lifestyle habits, maybe the risk of losing your brain power will light a fire.

See your primary care physician to get your LDL cholesterol, apolipoprotein B, and triglyceride levels measured. (I recommend you aim for a reading of less than 70 mg/dL for both LDL and apolipoprotein B.)

Then make lifestyle adjustments in nutrition, exercise, sleep, and stress, and take statins and coenzyme Q10, if recommended.