Terry Quinn, MD
Stroke publishes a regular review of recent, important clinical research from other journals. This Literature Synopses feature is intended for those working in stroke and related fields. However, important science should be shared with everyone who is interested, and not just the experts. When writing the Synopses, I complement the journal article with a plain language summary intended for a non-expert readership.
Stroke researchers, and indeed clinical researchers in general, are often guilty of focusing on a single aspect of a person’s physiology. Stroke researchers are primarily interested in the brain and its blood vessels, and so we may sometimes forget that those same blood vessels supply all the other organs of the body. People living with stroke rarely have stroke in isolation. In clinical practice, it is common to see a combination of stroke disease, heart disease, and kidney disease.
In this Literature Synopses published in Stroke, I looked at recent research papers that considered stroke and kidney disease together. I specifically chose the topic of kidney disease as it is a common, chronic condition and the number of people with kidney disease is increasing all the time.
Stroke and kidney disease are both so common that when they occur together, is this just chance? A study from Taiwan looked at people with differing severity of kidney disease and described the numbers that had a stroke. The study suggested that any relationship between stroke and kidney disease is not just coincidence. Kidney disease seems to increase the risk of a future stroke, and the more severe the kidney problem, the greater the risk of stroke. Depressingly, the same research team found that when people with kidney disease have a stroke, they are more likely to be disabled or to die. So, can we do anything to prevent this kidney disease and stroke ‘double whammy’?
We don’t really understand why kidney disease predisposes to stroke. The kidneys perform many functions in the body, including getting rid of waste products in the blood. When kidneys are damaged, we can use other methods to help. Kidney dialysis uses a machine to filter the blood, while a kidney transplant replaces the damaged kidney. In a study from Scotland, the researchers found that differing methods of dialysis were associated with a differing risk of stroke. However, no method of dialysis was as good as a renal transplant. There is a clear message for everyone here — register as an organ donor and let your family know your wishes.
The relationship between kidney disease and stroke may be due to a common factor, and heart disease may be the culprit. The heart rhythm disorder atrial fibrillation (AF — an irregular heart beat) is common in kidney disease and can cause stroke. Blood thinning medication can prevent the strokes caused by AF, but prescribing in kidney disease is not straightforward. Another role of the kidney is to process and excrete medications. When the kidney is very damaged, we need to be careful with the medications we prescribe. In a study from the UK, researchers found that people with kidney disease and AF were more likely to have bleeding side effects from blood thinning medication, but overall these medications seemed to prevent death.
Looking at these papers highlights that treating people with stroke becomes (even more) complicated when they also have other conditions such as kidney disease. However, having several long-term conditions is increasingly common, and stroke clinicians can’t ignore these other issues. From a research perspective, I was encouraged to see that many of the papers I came across made use of large databases. For example, here in Scotland, every person with new stroke and many attending a hospital with kidney disease are logged in a National register. These resources will help us understand how common conditions interact, and ultimately will help us manage patients better.
As with all my Literature Synopses, the views expressed are my own. You may agree or disagree or wish to comment, and I would be happy to hear from you at @DrTerryQuinn.
- Cherng YG, Lin CS, Shih CC et al. Stroke risk and outcomes in patients with chronic kidney disease or end stage renal disease: Two nationwide studies. PLOSone 2018:13(1): e0191155.
- Findlay M, MacIsaac R, MacLeod MJ et al. Renal replacement modality and stroke risk in end stage renal disease – a national registry study. Nephrol Dialysis Transplant 2017; 1-8.
- Kumar S, de Lusig S, McGovern A et al. ischaemic stroke, haemorrhage and mortality in older patients with chronic kidney disease newly started on anticoagulation for atrial fibrillation: a population based study from UK primary care. BMJ. 2018; 360:k342.