Association of Hypothyroidism and Mortality in the Elderly Population: A Systematic Review and Meta-Analysis

Abstract

Abstract Context The evidence of whether hypothyroidism increases mortality in the elderly population is currently inconsistent and conflicting. Objective The objective of this meta-analysis is to determine the impact of hypothyroidism on mortality in the elderly population. Data Sources PubMed, Embase, Cochrane Library, Scopus, and Web of Science databases were searched from inception until May 10, 2019. Study Selection Studies evaluating the association between hypothyroidism and all-cause and/or cardiovascular mortality in the elderly population (ages ≥ 60 years) were eligible. Data Extraction Two reviewers independently extracted data and assessed the quality of the studies. Relative risk (RR) was retrieved for synthesis. A random-effects model for meta-analyses was used. Data Synthesis A total of 27 cohort studies with 1 114 638 participants met the inclusion criteria. Overall, patients with hypothyroidism experienced a higher risk of all-cause mortality than those with euthyroidism (pooled RR = 1.26, 95% CI: 1.15-1.37); meanwhile, no significant difference in cardiovascular mortality was found between patients with hypothyroidism and those with euthyroidism (pooled RR = 1.10, 95% CI: 0.84-1.43). Subgroup analyses revealed that overt hypothyroidism (pooled RR = 1.10, 95% CI: 1.01-1.20) rather than subclinical hypothyroidism (pooled RR = 1.14, 95% CI: 0.92-1.41) was associated with increased all-cause mortality. The heterogeneity primarily originated from different study designs (prospective and retrospective) and geographic locations (Europe, North America, Asia, and Oceania). Conclusions Based on the current evidence, hypothyroidism is significantly associated with increased all-cause mortality instead of cardiovascular mortality among the elderly. We observed considerable heterogeneity, so caution is needed when interpreting the results. Further prospective, large-scale, high-quality studies are warranted to confirm these findings.