We've long known that a low level of HDL, or "good," cholesterol is associated with an increased risk of cardiovascular disease. To that end, doctors have been prescribing high doses of niacin (vitamin B3) to help increase HDL cholesterol to a normal range in people with low HDL levels.
The National Heart, Lung, and Blood Institute (NHLBI) funded a study that began in 2006 to determine whether niacin does, in fact, help prevent cardiac events. It turns out that, at least when taken with statins, it probably doesn't. In fact, the research so clearly demonstrated niacin's ineffectiveness when combined with a statin in preventing cardiac events that the NHLBI pulled the plug on the study 18 months earlier than planned.
A slight uptick in strokes among participants taking niacin also influenced the agency's decision to halt the study.
If you're currently taking prescription niacin, however, the study findings aren't reason to stop taking itespecially before speaking with your doctor. First, the study was inconclusive when it came to niacin's overall heart-health benefits. Second, your combined risk factors may be different from those of the study participants. Third, your doctor may have prescribed niacin for another reason, such as to help lower your LDL level. Although niacin doesn’t lower levels as much as statins do, it does so without risk of the muscle pain or the muscle disorder rhabdomyolysis that statins can cause.
The NHLBI’s AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides: Impact on Global Health) trial sought to determine whether high-dose, extended-release niacin was safe and could lower the risk of heart problems when combined with a statin. While the drug succeeded in raising HDL cholesterol, researchers found no evidence that it offered any health benefit to people taking a statin to lower their LDL cholesterol. They concluded that niacin, in that case, couldn't reduce risk of cardiovascular damage even though it raised HDL cholesterol.
Niacin has been thought to provide a health benefit to people with low HDL cholesterol and high triglycerides (a type of fatty substance in the blood). Earlier studies have shown a link between niacin and improved levels of HDL cholesterol (by 15 to 30 percent), LDL cholesterol (less than 10 percent) and triglycerides (15 to 20 percent).
However, AIM-HIGH chose a different approach when selecting participants. Instead of testing niacin on people with low HDL cholesterol and high LDL cholesterol, this study looked at people who had low HDL cholesterol and a healthy range of LDL cholesterol. The 3,414 study participants had several heart-health factors in common:
- Low HDL cholesterol
- Well-controlled, or low, LDL cholesterol as a result of using cholesterol-lowering statins
- High triglycerides
- A history of coronary artery disease
The patients, whose average age was 64, all had increased risk for cardiovascular events. More than half had previously had a heart attack, and about one-third had diabetes. Researchers randomly divided participants into two groups: One group took niacin and the other a placebo (an inactive pill with no medical value). Both groups continued to take the statin simvastatin (Zocor). Some participants were also given ezetimibe (Zetia), another type of cholesterol-lowering drug, to maintain an LDL cholesterol range of 40–80 mg/dL.
The brand of niacin used was Niaspan, an extended-release version of niacin meant to help lessen the unpleasant flushing the drug commonly causes. Participants took gradually increasing doses of up to 2,000 mg a day. Once participants started the drug regimen, researchers followed them for 32 months. During that time, researchers monitored them for certain heart and vascular conditions and events, including:
- Cardiovascular disease deaths
- Nonfatal heart attack
- Hospitalization for acute coronary syndrome (a sudden reduction of blood flow to the heart)
- Artery bypass surgery (to improve blood flow to the brain or heart)
Because AIM-HIGH was stopped before its original end date, the results reported above are preliminary.
Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50