Comorbidities including diabetes, heart failure (HF), stroke, chronic obstructive pulmonary disease (COPD), peripheral arterial disease (PAD), hyperlipidemia, hypertension, and cancer are common in patients with chronic kidney disease, particularly those receiving hemodialysis (HD). Even though it is established that comorbidities increase the risk of mortality in HD patients, the association of hypothyroidism and mortality in the presence of comorbidities is unknown. A study in Nephrology investigated the impact of comorbidities and hypothyroidism on all-cause mortality in HD patients.

In the study, investigators identified 908 patients with hypothyroidism and matched 3,632 patients without hypothyroidism from the Registry for Catastrophic Illness Patient Database of Taiwan Health Insurance from 2000 to 2010. Both groups included patients over age 20 years with newly diagnosed end-stage renal disease. There was no significant difference in the distributions of sex and age between the hypothyroidism group and nonhypothyroidism group. The proportion of patients with diabetes (P = .41), hyperlipidemia (P = .62), hypertension (P = .24), and PAD (P = .46) did not differ significantly between the two groups. However, the proportion of patients with CAD (P = .02), HF (P <.001), stroke (P = .005), COPD (P <.001), asthma (P = .006), and cancer (P <.001) was higher in the hypothyroidism group. Cox proportional hazards regression was used to analyze the association of hypothyroidism and risk of all-cause mortality.

The study revealed that hypothyroidism was associated with increased all-cause mortality with an adjusted hazard ratio of 1.22 [95% CI: 1.10–1.36, P <.001]. Thyroxine-replacement therapy may decrease mortality associated with hypothyroidism (P <.001). In a subgroup analysis, hypothyroidism was not associated with mortality in patients younger than age 65 years, patients without CAD, and those with cancer. Notably, there was a statistically significant interaction between diabetes and hypothyroidism (P = .04). No significant interactions were discovered between hypothyroidism and the following comorbidities: hyperlipidemia, hypertension, COPD, CAD, stroke, PAD, asthma, HF, and cancer.

The investigators concluded that thyroxine-replacement therapy might improve survival rates, while hypothyroidism is associated with increased all-cause mortality in chronic HD patients. Furthermore, it was demonstrated that the interaction of hypothyroidism and diabetes, but not other common comorbidities, in HD patients has an effect on mortality risk.

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