The effects of simvastatin and pravastatin on objective and subjective measures of nocturnal sleep: a comparison of two structurally different HMG CoA reductase inhibitors in patients with primary moderate hypercholesterolaemia.

1. It has been suggested that HMG CoA reductase inhibitors which are administered as inactive, lipophilic lactones (e.g. simvastatin) have a greater propensity to evoke nocturnal sleep disturbances than pravastatin, an inhibitor given in the active, hydrophilic, open-acid form. 2. The effects of 4 weeks treatment with equipotent doses of simvastatin (20 mg day-1) and pravastatin (40 mg day-1) have been compared using polysomnography and subjective sleep assessments in a double-blind, placebo-controlled, two-period, incomplete block design study involving 24 male patients with primary moderate hypercholesterolaemia (mean LDL cholesterol 5.11 mmol l-1). 3. Analysis of sleep EEG measures relevant to insomnia provided no evidence of significant differences between pravastatin, simvastatin and placebo, except in terms of entries and latency to stage I sleep. The number of entries to stage I sleep was significantly greater after simvastatin treatment than after either pravastatin or placebo (P < 0.05), but by contrast the latency to stage I sleep was significantly prolonged only in the pravastatin group (P < 0.05 vs placebo). 4. Subjective ratings of sleep initiation, maintenance and quality made during and after therapy were not significantly different between the three treatment groups. 5. It appears that the inherent hydrophobicity of simvastatin does not increase the occurrence of sleep disturbances in this patient population at a dose shown to elicit a characteristic hypolipidaemic response.