US researchers reported to a meeting of the American Heart Association’s Scientific Sessions 2007 this week that simvastain, a drug designed to lower cholesterol, could be the cause of disrupted sleep in some patients.

Previous research, using small studies, has found that some patients taking cholesterol lowering statins slept badly and even had nightmares.

This latest study, by Dr Beatrice Golomb, an associate professor of medicine and family and preventive medicine at the University of California at San Diego School of Medicine, and colleagues, reported to be the largest of its kind, compared two statins: simvastatin and pravastatin. The first is lipophilic (soluble in fats) and the second is hydrophilic (soluble in water).

The fat soluble simvastatin crosses into the brain from the blood more readily because it is fat soluble. Nerve circuits in the brain that control sleep could be affected if the fatty insulation around them, called myelin, stops working properly, thus allowing electrical signals to leak out or weaken.

The results of the study showed that the participants taking the fat soluble simvastatin were reporting significantly worse sleep quality than those on pravastatin or placebo, and in significantly greater numbers.

“On average, the lipophilic statin had a greater adverse effect on sleep quality,” Golomb said.

The research is important because quality of sleep affects quality of life and people’s health, said the researchers.

Earlier studies had compared different statins and one had found a difference in effect on sleep quality between prevastatin and simvastatin, said the researchers, but they were too small scale to be significant.

In this randomized, double-blind, placebo-controlled trial, Golomb and colleagues tested 1,016 healthy adult male and female patients over a six month period. The participants were in three groups. One group took 20 mg of simvastatin, another took 40 mg of pravastatin, and the third took a placebo.

The participants completed two types of questionnaire to assess impact on sleep before and during the treatment: a visual analogue scale and a rating scale.

Golomb said the participants also reported mood changes:

“Those who reported developing much worse sleep on study medication also showed a significant adverse change in aggression scores compared to others.” However, not all the patients on the fat soluble statin experienced these drawbacks, as Golomb pointed out:

“Although the average effect on sleep was detrimental on simvastatin, this does not mean that everyone on simvastatin will experience worse sleep.”

The study did not include patients with diabetes or heart disease because they may have had problems on placebos.

The researchers suggested patients who take simvastatin and are having sleep problems should talk to their doctor.

The study was funded by the the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH).

Lowering high levels of blood cholesterol reduces a person’s chances of having a plaque burst in their blood vessels and thereby reducing the risk of a heart attack. It can also slow down, reduce and even stop the plaque from building up.

The body uses cholesterol to make hormones, vitamin D, and enzymes that digest food.

Click here for NHLBI.

Click here for more information on cholesterol (MedlinePlus, NIH).

Written by: Catharine Paddock