The cholesterol-lowering drugs statins may reduce the likelihood of developing Alzheimer's disease reported seven newspapers (August 28th 2007). These reports were based on a study of 110 brains examined at post mortem. The newspapers generally reported the association found by the study accurately, including the need for cautious interpretation and further research.
-
On 28th August 2007 seven newspapers (1-7) reported that statins, normally prescribed to lower cholesterol, may also reduce the likelihood of developing Alzheimer's disease.
-
The newspaper reports were based on a case control study which investigated the association between previous statin use and the presence of signs of Alzheimer's disease in 110 brains at post mortem (8). After adjustment for other variables, incidence of neurofibrillary tangles was lower in the brains of individuals classified as statin users than in the brains of non-users.
-
The newspaper reports of the study were broadly accurate. However it may not be explicitly clear from all the reports that the research examined brain changes associated with Alzheimer's Disease, not the impact of taking statins on developing the clinical disease itself. Two newspapers stated that the reduction in incidence of neurofibrillary tangles was found even after controlling for variables such as age (5, 6). In fact the study did not find a statistically significant difference unless the data were adjusted for these factors.
Evaluation of the evidence base for an association between statin therapy and reduced neuropathologic changes of Alzheimer's disease.
Where does the evidence come from?
The study was a collaboration led by Dr Gail Li and involved researchers from the University of Washington, the Mental Illness Research and Education Clinical Center, the Geriatric Research, Education and Clinical Center, the Veterans' Affairs Puget Sound Health Care System, and the Center for Health Studies Group Health Cooperative in Seattle, USA. The research was partially funded by the USA National Institute on Aging.
What were the authors' objectives?
To investigate whether statin exposure is associated with incidence of neurofibrillary tangles and neuritic plaques; neuropathologic indicators of Alzheimer's disease.
What was the nature of the evidence?
Post mortem examinations were conducted on 110 brains to assess the incidence of neurofibrillary tangles, neuritic placques and overall presence of Alzheimer's disease pathology. The sample of people who agreed to a brain dissection after death were recruited from the Adult Changes in Thought (ACT) cohort study. Participants were cognitively normal and aged 65 or over at the time of recruitment into the study. To control for age related differences in exposure to statins only people under 80 years at the time of recruitment were eligible for the investigation of statins. 2,523 were aged under 80 at recruitment, of whom 608 had died by 31st July 2006. The 110 (18%) of individuals who had consented to brain dissection differed from the overall cohort population on key demographic variables (age, gender and race).
Individuals were classified as statin users if the pharmacy database showed that they had received at least three prescriptions (of at least 15 pills) for statins, and as non-users if they had received fewer. There were a number of differences between the groups, with statin users more likely than non-users to be male, to smoke, to be diabetic, suffering from cardiovascular disease, or to have higher total cholesterol and lower HDL cholesterol. The incidence of all cause dementia prior to death was similar in the two groups.
How did participants differ on their level of exposure to the factor of interest?
The lipid-lowering agents statins were examined in the study. Of the 110 post mortem examinations, 36 were statin users. The majority of individuals classified as statin users were prescribed simvastatin (58%) or lovastatin (33%).
What were the findings?
There were no statistically significant differences between statin users and non-users in incidence of neurofibrillary tangles, neuritic plaques, or overall presence of Alzheimer's pathology.
When results were adjusted for age at death, gender, entry score on the Cognitive Abilities Screening Instrument (CASI), presence of microvascular lesions and brain weight, statin users were less likely to have neurofibrillary tangles than non-users and this was statistically significant. There was no significant difference between the groups in the presence of neuritic plaques. Statin users had a significantly lower likelihood of the presence of Alzheimer's pathology than non-users.
What were the authors' conclusions?
The authors concluded that there is an association between statin use and decreased neurofibrillary tangle burden at post mortem. They also state that further research is required to assess whether there is a causal link between the use of statins and reduced development of the neuropathological changes associated with Alzheimer's disease.
How reliable are the conclusions?
The conclusions are based on a study of 110 brains examined at post mortem. The authors accurately state that their data support only an association between statin use and decreased incidence of the neurofibrillary tangles that are characteristic of Alzheimer's Disease. Trials are required to establish whether there is a causal relationship between statin use and developing Alzheimer's. There is a high risk that other factors may have influenced the findings and, as stated by the authors, the findings should be extrapolated to living populations with the greatest caution, if at all.
Systematic reviews
Information staff at CRD searched for systematic reviews relevant to this topic. Systematic reviews are valuable sources of evidence as they locate, appraise and synthesize all available evidence on a particular topic.
There was one related systematic review identified on the Cochrane Database of Systematic Reviews (CDSR) (10) and two on the Database of Abstracts of Reviews of Effects (DARE) (11, 12).
References and resources
1. Statins 'may ease risk of dementia'. The Daily Telegraph, 28 August 2007, p1.
2. 79% less chance of Alzheimer's if you take statins. Daily Mirror, 28 August 2007, p22.
3. Alzheimer's hope. The Sun, 28 August 2007, p19.
4. The pill that can slash your risk of Alzheimer's. Daily Express, 28 August 2007, p20.
5. How statins can help to protect from Alzheimer's. Daily Mail, 28 August 2007, p12.
6. Statins 'help to prevent Alzheimer's disease'. The Independent, 28 August 2007, p6.
7. Researchers find statins slow onset of Alzheimer's. The Guardian, 28 August 2007, p15.
8. Li G, Larson EB, Sonnen JA, Shofer JB, Petrie EC, Schantz A, Peskind ER, Raskind MA, Breitner JCS, Montine TJ. Statin therapy is associated with reduced neuropathologic changes of Alzheimer disease. Neurology 2007;69:878-885.
9. Silbert LC. Does statin use decrease the amount of Alzheimer disease pathology in the brain? Neurology 2007;69:8-11.
10. Laake K. Statins for the prevention of Alzheimer's disease. Cochrane Database of Systematic Reviews 2001, Issue 3. Art. No.: CD003160. DOI: 10.1002/14651858.CD003160.
11. Etminan M, Gill S, Samii A. The role of lipid-lowering drugs in cognitive function: a meta-analysis of observational studies. Pharmacotherapy 2003; 23(6) 726-730. [DARE Abstract]
12. Xiong G L, Benson A, Doraiswamy P M. Statins and cognition: what can we learn from existing randomized trials? CNS Spectrums 2005 10(11) 867-874. [DARE Abstract]
Consumer information
Alzheimer's Society
Alzheimer's Research Trust
NHS Direct - Alzheimer's disease
Further information about Hitting the Headlines
Further information about Hitting the Headlines, together with selected relevant links, can be found at http://www.library.nhs.uk/hth/.
