What do “cognitive impairment” and “brain fog” mean in CKD?
Many people with chronic kidney disease (CKD) notice changes in how they think and process information.
Anyone can experience slow thinking and poor concentration from time to time, but these symptoms may be more likely when you’re living with CKD. Doctors might describe this as “cognitive impairment”, and it’s often referred to informally as “brain fog”. Symptoms range from mild and occasional to more noticeable.
There are lots of different reasons people with CKD may experience brain fog. Some are directly linked to changes in kidney function, but mood, sleep and other lifestyle factors can also play a role.
What symptoms of brain fog should I look out for?
Symptoms vary, but can include:
- difficulty concentrating
- forgetfulness
- slower thinking or mental fatigue
- trouble making decisions or planning
- occasionally feeling disoriented or overwhelmed
You might also notice emotional changes, such as feeling more anxious, low or irritable.
These symptoms can come and go, and you might notice them more when you’re tired or unwell.
How does CKD affect the brain?
Reduced kidney function can affect the brain in several different ways. “The exact causes of brain fog in people with CKD aren’t clear,” says transplant nephrologist Dr Aditi Gupta, who has studied cognitive impairment in CKD.
- As kidney function changes, waste products (uraemic metabolites) can build up in the blood and affect brain cells.
- CKD is also linked to high blood pressure and changes in blood vessels, which can reduce blood flow to the brain.
- Anaemia (low red blood cells) and changes in blood chemistry can also affect how clearly you think.
Can stress or anxiety make brain fog worse?
Yes – psychological causes like low mood and anxiety are part of the puzzle.
Living with a long-term condition can be challenging for anyone, and CKD is strongly linked with stress, anxiety and low mood, all of which can affect concentration, memory and sleep.
And if you’ve noticed signs of brain fog, that may further affect your mood. “Cognitive impairment can lead to low self-esteem, depression and anxiety, and may affect different areas of your life, including relationships and work,” says Dr Gupta.
It can become a cycle: brain fog can make daily life feel harder, which impacts your mood. Stress and low mood can, in turn, make thinking feel more difficult.
How common is cognitive impairment in CKD?
Research shows that 4 in 10 people with CKD experience brain fog. It’s more common and noticeable in the later stages (CKD4 and CKD5), when factors like higher levels of uraemic toxins and inflammation have a greater impact. But some people find their thinking is affected in earlier CKD.
However, not everyone will notice symptoms. Changes may be mild, and they don’t always get worse over time.
How are dialysis patients affected?
Studies suggest around half of people on dialysis may experience some degree of impairment. Cognitive changes may also be more noticeable in people on dialysis.
This is linked to a combination of factors, including bigger swings in blood flow to the brain during dialysis, which can, over time, lead to small areas of damage.
By the time someone needs dialysis, kidney function is usually very low so there may be higher levels of inflammation and uraemic toxins, and more advanced changes in the brain’s blood vessels.
Plus, many people on dialysis have sleep disorders, such as insomnia and restless legs, which can contribute to problems with memory, attention and decision-making.
What about brain fog after a kidney transplant?
“Cognitive impairment is at least partly reversible through transplant,” says Dr Gupta. Some aspects of thinking, such as how you remember events and learned information, may go back to normal, while other areas, including language and thinking speed, may improve at least to some degree.
A transplant may reverse changes such as differences in blood flow, chemical balance and the brain’s internal 'wiring', says Dr Gupta: “MRI brain scans in people with CKD often show changes that improve after their kidney function is restored with a transplant.”
Cognitive symptoms don’t always go away completely. Some people continue to experience mild difficulties, possibly due to earlier changes in blood vessels or the effects of long-term treatment. But many find they can think more clearly after a transplant.
Does CKD mean I’m more likely to develop Alzheimer’s?
CKD is linked to a higher risk of dementia but that doesn’t mean you’ll develop Alzheimer’s disease. Researchers think the link may be partly due to the fact that the brain and kidneys share similar small blood vessels. Conditions that affect these blood vessels, such as diabetes and high blood pressure, may affect both organs over time.
Many of these risk factors are manageable through keeping to your treatment plan, taking your medicines as directed and looking after your brain and kidney health with lifestyle measures like a balanced diet and good sleep.
How to support your brain health with CKD
The reassuring news is that there are many ways to support your brain health when you’re living with CKD.
Your healthcare team will treat the underlying contributing factors, for example:
- keeping blood pressure well controlled
- managing anaemia if necessary
- reviewing medications
- optimising dialysis or post-transplant care
“Brain fog can make it harder to follow dietary changes and take your medicines,” says Dr Gupta – so speak to your healthcare team if you’re struggling, as they may have suggestions to help.
Alongside your treatment plan, lifestyle and psychological support can make a real difference. For example:
- regular physical activity
- good sleep and nutrition
- exercising your brain with activities like reading, puzzles and socialising
- support for stress, anxiety or low mood, such as talking therapies
Even small changes can help improve clarity and confidence over time.
Always speak to your healthcare team if you’re concerned about brain fog – it’s a common issue and they can work with you to manage it.