Statins may reduce risk of Alzheimer's disease

Patients taking the statin class of cholesterol lowering drugs may derive the extra benefit of a reduction in risk of Alzheimer's disease, according to a new study (Archives of Neurology 2000;57:1439-43).

As high levels of cholesterol have been associated with Alzheimer's disease, and a cholesterol transport isoprotein, apolipoprotein E4, is known to increase the risk of the disease, the study authors set out to determine if statins could reduce the incidence of Alzheimer's disease.

Led by Dr Benjamin Wolozin of Loyola University Medical Center in Maywood, Illinois, and Paul Rousseau of the Carl T Hayden Veteran Affairs Medical Center in Phoenix, Arizona, the researchers conducted a multicentre, cross sectional analysis that examined the relation between treatment with statins and the diagnosis of probable Alzheimer's disease.

Alzheimer's disease was diagnosed in patients with clinical evidence of progressive cognitive impairment in more than one area by using criteria developed at the National Institute of Neurology, which is part of the National Institutes for Health in Bethesda, Maryland, along with mini-mental status examinations and neuropsychological testing.

Metabolic and toxic screens, as well as computed tomography and magnetic resonance imaging, were used to exclude other causes of dementia. The investigators culled databases from three hospitals to compare the prevalence of Alzheimer's disease in patients aged 60 years and older.

The population was subdivided into three general groups: the study population as a whole, patients receiving statins, and patients receiving drugs used to treat cardiovascular disease or hypertension.

The researchers focused on three statins—lovastatin, pravastatin, and simvastatin. In all, information on over 60 000 patients was reviewed. To maximise the statistical power of their analysis, the authors combined the results from the three sites.

The researchers reported that the study results were similar across the three medical centres and that patients receiving lovastatin or pravastatin—but not simvastatin—had a 70% lower prevalence of Alzheimer's disease than the entire patient population aged 60 and older (P<0.001 for each site).

Moreover, patients receiving statins had a lower incidence (by 57-73%) of Alzheimer's disease than patients receiving b blockers (by 73%), frusemide (furosemide) (by 57%), or captopril (by 64%).

The comparison with other cardiovascular drugs was performed as a sort of control, as patients taking such drugs might be expected to have a similar incidence of Alzheimer's disease.

No reduction was found in the rates of transient ischaemic attack among patients taking statins compared with other cardiovascular drugs. Patients taking cardiovascular drugs, including the statins, had higher rates of transient ischaemic attack than did the general patient population aged over 60, reflecting the higher prevalence of vascular disease in the cohort.

Simvastatin treatment failed to reduce the incidence of Alzheimer's disease, despite being structurally related to pravastatin. The investigators concluded that the inverse association between statins and risk of Alzheimer's disease warrants further study and should be tested with rigorous clinical trials because of its considerable potential therapeutic importance.