Increased risk of chronic kidney disease in schizophrenia

"After adjusting for demographic characteristics, select comorbid medical disorders and NSAIDs [non-steroid anti-inflammatory drugs] usage, the current results reveal that patients with schizophrenia have an increased risk of nearly 40% (HR=1.36; 95% CI 1.13 to 1.63; p<0.001) of developing CKD [chronic kidney disease] within a 3-year follow-up period after their schizophrenia diagnosis."

That was the rather surprising finding reported by Nian-Sheng Tzeng and colleagues [1] (open-access) following their interrogation of the national research database which continues to give based in Taiwan. I've talked about the very, very useful data emerging from the Taiwanese National Health Insurance Research Database (NHIRD) before on this blog quite a few times (see here for example) and it's world-leading role in various research areas. I'm particularly impressed with the use of this resource when it comes to the intersection between psychiatry and physical health as per the evidence that something like asthma might for example have a connection to autism or ADHD [attention deficit hyperactivity disorder] (see here and see here respectively). Yes, I know correlation is not the same as causation, but the prospective design of some of  this research and the sheer numbers of participants involved should really be stimulating quite a bit more interest in such associations.

Anyhow, back to the recent Tzeng paper:

• Chronic kidney disease (CKD) is all about the kidneys "not working as well as they once did." The kidneys serve quite a few important functions including getting rid of our waste products and aiding the reabsorption of various nutrients. The kidneys also help regulate blood pressure. CKD - which has various stages - has several potential causes, notably diabetes and high blood pressure (hypertension).
• Researchers located some 2300 people diagnosed with schizophrenia from the NHIRD and matched them 3:1 with over 7000 people not diagnosed with schizophrenia. Age, gender and level of urbanisation were some of the matching factors.
• Results: "A comparison with controls revealed that patients with schizophrenia were more likely to have the comorbidities of diabetes mellitus..., hypertension... and hyperlipidaemia. Patients with schizophrenia were more likely to take NSAIDs..." NSAIDs also have a connection to CKD as per data such as that from Gooch and colleagues [2]. What this all means is that participants with schizophrenia were already more likely to present with some of the risk factors for CKD over and above controls.
• Over the course of 3-years of follow-up "528 (3.21%) of the 9352 study patients experienced CKD" which in proportional terms was weighted towards more participants with schizophrenia presenting with CKD over controls. "The incidence rate (per 1000 person-years) of CKD for patients with schizophrenia (25.13) was higher than that for non-schizophrenic controls (18.60)."
• The authors conclude: "we found a significant association, a 25% increased risk, between schizophrenia and subsequent CKD in a 3-year follow-up period, especially in those older ages, those with DM [diabetes mellitus] and those using NSAIDs." And with that comes the important idea that further research on the merit of preferential screening for CKD in cases of schizophrenia might be indicated.

I have little more to say about this study and the important conclusions reached. The idea that physical / somatic health issues perhaps don't receive the research or clinical interest they deserve where and when a psychiatric or behavioural diagnosis is received is becoming an all-too frequent theme on this blog. Be it heart health and schizophrenia (see here) or something like medical comorbidity and autism (see here), there remains something of a disjoin between psychological health and physical health and the acceptance that people with diagnoses such as schizophrenia are people first and so at least as likely as every else to present with physical health issues. Added to the idea that a label such as schizophrenia might predispose a person to be more likely to partake in activities such as tobacco smoking [3] and/or be overweight / obese [4] as a function of lifestyle or medication (see here), the focus on improving psychiatric outcome in cases of schizophrenia should really be going hand-in-hand with ensuring physical health is also catered for and the risk of chronic disease, even early mortality [5] is kept to a minimum.

Music to close: Morrissey with Suedehead.

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[1] Tzeng N-S. et al. Is schizophrenia associated with an increased risk of chronic kidney disease? A nationwide matched-cohort study. BMJ Open 2015; 5: e006777.

[2] Gooch K. et al. NSAID Use and Progression of Chronic Kidney Disease. American Journal of Medicine. 2007; 120: 280.e1–280.e7.

[3] Kelly C. & McCreadie R. Cigarette smoking and schizophrenia. Advances in Psychiatric Treatment. 2000; 6: 327-331.

[4] Hjorth P. et al. A systematic review of controlled interventions to reduce overweight and obesity in people with schizophrenia. Acta Psychiatr Scand. 2014 Oct;130(4):279-89.

[5] Hsu WY. et al. A population-based cohort study on deep vein thrombosis and pulmonary embolism among schizophrenia patients. Schizophr Res. 2015 Jan 23. pii: S0920-9964(15)00016-X.

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Tzeng, N., Hsu, Y., Ho, S., Kuo, Y., Lee, H., Yin, Y., Chen, H., Chen, W., Chu, W., & Huang, H. (2015). Is schizophrenia associated with an increased risk of chronic kidney disease? A nationwide matched-cohort study BMJ Open, 5 (1) DOI: 10.1136/bmjopen-2014-006777