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Do statins reduce the risk of dementia?

Posted Sep 19 2013 9:21pm

Last month I noticed several reports in the news about a study concerning the relationship between statins and dementia (see here for an example). The study in question was presented at a cardiology conference in Amsterdam, the Netherlands. This research found that, over a 4 and a half-year period, statin use was associated with a significantly reduced risk of developing Alzheimer’s disease. I saw a cardiologist comment on this study on the TV. He talked about previous concerns that statins might adversely affect brain function, and how this new study can give us confidence that statins are safe after all in this respect.

This study, from Taiwan, is epidemiological in nature, which means all it’s really good for is establishing the relationship between statins and Alzheimer’s disease. It does not, actually, tell us much about what the effects statins have on the brain. This is partly because the supposed benefits of taking statins may not be due to the statins at all, but due to other factors associated with the taking of statins.

One potential so-called ‘confounding factor’ here is the fact that, by and large, those who see doctors and take medications as prescribed are generally more health-conscious than those who don’t. For example, these people may be less likely to and be more likely to take exercise. It may be these or other factors, and not the statins per se, that are responsible for the lower risk of Alzheimer’s disease seen in those who take statins.

This sort of bias is further compounded by the fact that one of the reasons people may not take statins is because they tried them in the past, but had side-effects such as fatigue and muscle pain. It is possible, then, that those who tolerate statins are generally healthier than those who do not – another factor that can bias results in favour of statin-takers.

Anyone who has suffered mental symptoms such as memory lapses and confusion as a result of taking statins is quite likely to stop taking them and may appear in the ‘no-statin’ group. In this way, genuine problems with statins may effectively disappear from the statistics, making statins appear better and safer than they are in reality.

To properly assess the effect of statins on the brain we need to look at data from ‘clinical’ studies, such as those where individuals are treated with a statin or placebo and the effects compared. Unfortunately, even here there can be biases that can skew results. For example, as I mentioned in a blog post last week, many studies include a ‘run-in’ period where all potential study subjects are given the active drug. Those who react adversely to the statin are then removed from the study before it starts in earnest. Again, this can make statins look safer than they are in reality.

Despite this sort of bias, clinical studies are still generally more illuminating than epidemiological ones. Unfortunately, there is not a lot of clinical evidence relating to statins and dementia. That’s partly because many studies have simply failed to record dementia as a potential side effect.

However, in 2010 researchers from the respected ‘Cochrane Collaboration’ conducted a review of the clinical evidence regarding the impact of statin therapy on mental symptoms in individuals with a diagnosis of dementia [1]. The review isolated three relevant studies (lasting 26, 52 and 72 weeks respectively). When the results of these studies were put together, there was no evidence of improvement in the symptoms of dementia, though there was no evidence of harm either.

My clinical experience tells me that statins can indeed have adverse effects on brain function, and this is a recognised issue. The Food and Drugs Administration in the US, for instance, has alerted us to the potential for problems here by warning us that: “There have been rare post-marketing reports of cognitive impairment (e.g., memory loss, forgetfulness, amnesia, memory impairment, confusion) associated with statin use.”

Also, last year saw the publication of some interesting clinical research in which elderly individuals with Alzheimer’s disease had their statin medication stopped for six weeks, and then restarted [2]. The results showed that during the six weeks when their statins were stopped, the basic brain function of the individuals improved. When the drugs were restarted, brain function got worse again. One possibility here is that the changes were as a result of the placebo effect. However, it may also be true that the statins can genuinely worsen the symptoms of some people with Alzheimer’s disease or other forms of dementia.

References:

1. McGunness B, et al. Statins for the treatment of dementia. The Cochrane Library 2010

2. Padala KP. Et al. The effect of HMG-CoA reductase inhibitors on cognition in patients with Alzheimer’s dementia: a prospective withdrawal and rechallenge pilot study. Am J Geriatr Pharmacother. 2012;10(5):296-302

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