How often does mild kidney disease come with other illnesses?
Almost everyone with moderate chronic kidney disease in primary care had other chronic conditions, and having more of them was linked to a higher risk of dying.
Source
The burden of comorbidity in people with chronic kidney disease stage 3: a cohort study
Study at a glance
- Design
- Cohort — Prospective cohort (Renal Risk in Derby) recruited from 32 English general practices, with baseline comorbidity and medication counts and linked death records over a mean of 3.6 years.
- N
- N=1741 · 1741 people with CKD stage 3 recruited and analysed; 175 died during follow-up.
- Population
- Mostly older, white adults with chronic kidney disease stage 3 managed in English primary care
- Outcome
- Number of comorbidities (from a list of eleven) and medications at baseline; all-cause mortality during follow-up
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What they did
The researchers recruited 1741 people with stage 3 chronic kidney disease from 32 general practices in Derbyshire, England. At a baseline visit they recorded eleven common comorbidities (such as hypertension, diabetes, heart disease, depression and chronic pain), counted each person's regular medications, and took blood and urine samples. They then followed participants through national death records and used Cox regression to relate the number of comorbidities to all-cause mortality, adjusting for age, sex, education, deprivation, smoking, BMI and kidney function.
What they found
Only 78 of 1741 participants (4%) had kidney disease with none of the listed comorbidities, while 40% had more than two. The median person took five medications, 59% took five or more and 11% took ten or more; heavier medication use went with more comorbidities, older age, smoking, higher BMI, lower kidney function and lower education. Over a mean follow-up of 3.6 years, 175 people (10%) died, most often from cardiovascular disease. Having three or more comorbidities was linked to roughly three times the risk of death compared with none or one after adjusting for sociodemographic factors (hazard ratio 3.15), and comorbidity count stayed an independent predictor in the fully adjusted model.
The limits
What it doesn't show
There was no comparison group without kidney disease, so the study cannot say how much of this multimorbidity is specific to CKD rather than to ageing. Several conditions (depression, respiratory disease, chronic pain, thyroid disorder) were defined only by medication use and others by self-report, so some were probably missed, and cancer, liver disease, frailty and disease severity were not captured. Participants were volunteers who could attend their GP surgery and were almost all white, so the sample may be healthier and less diverse than the wider CKD population. As an observational study it shows association with mortality, not that comorbidities themselves cause the deaths.
Key terms
- Chronic kidney disease stage 3
- A moderate reduction in how well the kidneys filter blood, measured by estimated glomerular filtration rate (eGFR), and usually managed in primary care.
- Multimorbidity
- Having two or more chronic health conditions at the same time.
- Polypharmacy
- Regular use of many medicines, often defined as five or more; here used as a marker of treatment burden.
- Burden of treatment
- The work patients must do to manage their conditions, weighed against their capacity to cope with it.
- Cox proportional hazards model
- A regression method for time-to-event data that estimates how a factor changes the rate (hazard) of an outcome such as death.
Flashcards
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Quiz yourself
Roughly what share of participants with CKD stage 3 had none of the eleven listed comorbidities?
Common questions
Why does it matter that CKD rarely occurs alone?
Treatment guidelines often picture a patient with only reduced kidney function, but in practice most patients also have hypertension, diabetes, pain or heart disease, which adds medicines, interactions and self-management work that care plans need to account for.
Does this prove that having more illnesses causes earlier death in CKD?
No. It shows that more comorbidities are associated with higher mortality after adjusting for measured factors, but unmeasured differences such as frailty or disease severity could explain part of the link.
Why might the reported comorbidity levels be underestimates?
Some conditions were only counted if the person took a specific medicine, others relied on self-report, and volunteers who could attend clinic visits are probably healthier than average.
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