Thirty percent of North Americans over the age of 85 suffer from dementia. A recent study shows that people whose blood cholesterol levels varied the most over a 12 year period had a 19 percent increased risk for Alzheimer’s dementia compared to those with little or no variability, and people who had high variations in their triglyceride levels had a 23 percent increased risk for Alzheimer’s disease (Neurology, September 12, 2023;101(11):e1127-e1136).

A previous study found that total cholesterol variability is associated with increased dementia risk (Front Neurol, 2019;10(441). This increased risk for dementia was not associated with taking or not taking cholesterol-lowing medication. The authors feel that damage to the inner lining of arteries caused by high cholesterol and triglycerides is the cause. Many studies show that high cholesterol is associated with the arterial damage with decreased blood flow to the brain that is typical of dementia (Lancet, Aug 2021;2(8):e498-e506). This does not explain why variability in cholesterol and triglycerides is associated with increased risk for dementia. I think that this suggests, but does not prove, that people over 60 with high cholesterol or triglyceride blood levels who try, but fail to maintain, reduced levels of these risk factors with drugs and/or lifestyle changes are at increased risk for becoming demented. No associations were found between becoming demented and taking cholesterol-lowering medications, or variability in levels of the bad LDL and good HDL cholesterol.

Risk Factors for Dementia are the Same as for Heart Attacks
Dementia has the same risk factors that heart attacks do (Dementia, Aug, 2021;2(8):e498-e506), and reducing and keeping cholesterol and triglycerides low is a likely way to reduce dementia risk. Several previous studies have shown that variability in the bad LDL and good HDL cholesterol and triglycerides increased risk for heart attacks independent of levels and cholesterol-lowering treatment (J Clin Lipidol, 2018;12(2):356-366).

Variation in fasting blood sugar, total cholesterol, systolic blood pressure, and body fat (BMI) are associated with increased risk for death from a heart attack or stroke (Eur Heart J, 2017;38(48):3560-3566), so going on and off heart attack-preventing medications and lifestyle changes may be risk factors for dementia as they are for heart attacks. The same arterial damage that causes heart attacks also appears to increase risk for blood vessel damage in dementia (Neurobiol Aging, 2014;35(2):373-377) and may increase dementia risk as well (Lancet Neurol, 2004;3(3):184-190).

Many Studies Show that Major Lifestyle Changes Reduce Heart Attack Risk
• The Blood Cholesterol Expert Panel from the American College of Cardiology and the American Heart Association recommend that patients older than 21 years of age who have an LDL cholesterol level of more than 191 mg/dL be placed on high-intensity statin therapy to lower the LDL cholesterol levels by at least 50 percent (Circulation, 2014;129(25, suppl 2):S1-S45). However, this regimen is so loaded with significant side effects that doctors should recommend lifestyle changes to accompany the drugs and that people should get off or reduce the drugs as soon as they can.
• Moderate substitution of saturated fatty acids (meat) with polyunsaturated fatty acids (plants) lowers LDL cholesterol by about 10 percent, while going on a plant-based diet of fruits, vegetables, whole grains, beans, seeds and nuts that is also low in saturated fats (meat) can reduce LDL cholesterol by about 20 percent (Nutrients, Mar, 2023;15(5):1249).
• Highly-motivated people can lower their blood cholesterol with lifestyle changes. Six weeks on a diet and exercise program lowered total cholesterol by 40 percent and bad LDL cholesterol by 52.8 percent to normal. Six months later all cholesterol levels remained normal (Am J Lifestyle Med, 2019 Mar-Apr; 13(2): 148-155).

My Recommendations
If your bad LDL cholesterol is greater than 100 mg/dL, your good HDL cholesterol is lower than 40, or your triglycerides are greater than 150, you are at significant risk of a heart attack and for dementia. Most doctors will recommend medication, but taking medication without also changing lifestyle factors dramatically may not protect you, especially if your blood cholesterol factors go back up.
Heart Attack Prevention Guidelines