Increased Mortality in Chronic Hypoparathyroidism: A Nationwide Cohort Study in Sweden

Context: Previous studies on mortality outcomes in patients with chronic hypoparathyroidism have reported inconsistent results. Objective: To assess all-cause and cause-specific mortality and estimate the prevalence of chronic hypoparathyroidism in Sweden. Methods: Chronic hypoparathyroidism was defined as the combination of ICD-10 diagnoses and long-term dispensations of active vitamin D. Nationwide diagnostic codes, drug dispensation and mortality data were obtained from the National Patient Register, Prescribed Drugs Register, Cause of Death Register, and the Total Population Register. Mortality was compared between groups using Cox proportional hazards models, adjusting for age and baseline comorbidities. Results: We identified 1,982 individuals with chronic hypoparathyroidism between 1997 and 2018, yielding a minimum prevalence of 19.4 per 100,000 inhabitants. We randomly selected 19,820 controls matched by age, sex and county of residence. After excluding individuals with baseline thyroid cancer and their controls, 1,825 patients and 17,922 controls remained. Patients had higher all-cause mortality than controls (HR 1.55; 95% CI: 1.40-1.72). Mortality was higher in patients with nonsurgical (HR 2.16, 95% CI: 1.76-2.65) than postsurgical hypoparathyroidism (HR 1.39, 95% CI: 1.23-1.58). The strongest associations were observed for endocrine, nutritional and metabolic disorders (HR 6.46, 95% CI: 2.43-17.21), followed by infectious diseases (HR 3.53, 95% CI: 2.07-6.04), genitourinary diseases (HR 2.40, 95% CI: 1.33-4.33), respiratory diseases (HR 1.67, 95% CI: 1.23-2.28), and circulatory diseases (HR 1.47, 95% CI: 1.23-1.77). Conclusion: Patients with chronic hypoparathyroidism have an elevated risk of all-cause mortality, particularly those with nonsurgical disease. These findings highlight the clinical burden of the disease.