Diagnosis of hyponatremia and increased risk of a subsequent cancer diagnosis: results from a nationwide population-based cohort study

Abstract

Background: Hyponatremia has recently been associated with subsequent cancer risk. This population-based nationwide study assessed whether the diagnosis of hyponatremia can predict a cancer diagnosis within most common cancers.Material and methods: Using Danish medical registries, we identified 16,220 patients with a first-time diagnosis of hyponatremia, without a cancer diagnosis, from January 2006 through November 2013. We quantified the relative risk of a subsequent cancer diagnosis by standardized incidence ratios (SIRs), comparing observed cancer incidence among patients diagnosed with hyponatremia to that expected, based on national cancer incidence during that period.Results: During 40,207 person-years of follow-up, we observed 1546 cancer diagnoses compared to 956 expected (SIR: 1.62; 95% confidence interval (CI), 1.54–1.70). The increase in risk of a cancer diagnosis following a hyponatremia diagnosis was most pronounced within 0–6 months of follow-up (SIR 4.16; 95% CI, 3.85–4.48) and in the younger age group; 0–29 years (SIR 8.71; 95% CI, 2.82–20.28), 30–49 years (SIR 3.16; 95% CI, 2.26–4.31), 50–69 years (SIR 2.29; 95% CI, 2.10–2.48) and 70 + years (SIR 1.35; 95% CI, 1.27–1.44). Within six months after a hyponatremia diagnosis, the SIRs increased 10-fold for cancers of the lung (SIR 17.14; 95% CI, 15.15–19.32), brain (SIR 13.52; 95% CI, 8.90–19.66) and liver (SIR 13.26; 95% CI, 7.57–21.53) and increased 5 to 10-fold for cancers of the pancreas (SIR 8.25; 95% CI, 5.72–11.53), esophagus (SIR 6.59; 95% CI, 3.15–12.12), kidney (SIR 6.36; 95% CI, 3.39–10.88), pharynx (SIR 6.15; 95% CI, 1.27–17.97) and non-Hodgkin lymphoma (SIR 6.10; 95% CI, 4.17–8.61). The rate increased across virtually all types of cancers, except melanoma and basal cell carcinomas.Conclusions: A diagnosis of hyponatremia may be a marker of occult neoplasms, especially cancers of the lung, brain, liver, pancreas, esophagus, kidney, pharynx and non-Hodgkin lymphoma. Hyponatremia may aid in early detection of cancer.