What is the association of hypothyroidism with risks of cardiovascular events and mortality? A meta-analysis of 55 cohort studies involving 1,898,314 participants.
BACKGROUND
Whether hypothyroidism is an independent risk factor for cardiovascular events is still disputed. We aimed to assess the association between hypothyroidism and risks of cardiovascular events and mortality.


METHODS
We searched PubMed and Embase from inception to 29 February 2016. Cohort studies were included with no restriction of hypothyroid states. Priori main outcomes were ischemic heart disease (IHD), cardiac mortality, cardiovascular mortality, and all-cause mortality.


RESULTS
Fifty-five cohort studies involving 1,898,314 participants were identified. Patients with hypothyroidism, compared with euthyroidism, experienced higher risks of IHD (relative risk (RR): 1.13; 95% confidence interval (CI): 1.01-1.26), myocardial infarction (MI) (RR: 1.15; 95% CI: 1.05-1.25), cardiac mortality (RR: 1.96; 95% CI: 1.38-2.80), and all-cause mortality (RR: 1.25; 95% CI: 1.13-1.39); subclinical hypothyroidism (SCH; especially with thyrotropin level ≥10 mIU/L) was also associated with higher risks of IHD and cardiac mortality. Moreover, cardiac patients with hypothyroidism, compared with those with euthyroidism, experienced higher risks of cardiac mortality (RR: 2.22; 95% CI: 1.28-3.83) and all-cause mortality (RR: 1.51; 95% CI: 1.26-1.81).


CONCLUSIONS
Hypothyroidism is a risk factor for IHD and cardiac mortality. Hypothyroidism is associated with higher risks of cardiac mortality and all-cause mortality compared with euthyroidism in the general public or in patients with cardiac disease.
Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Yu
Y
Ning
Department of Cardiology, the Eastern Hospital of the First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China.
Yun J
YJ
Cheng
Department of Cardiology, the Eastern Hospital of the First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China.
Li J
LJ
Liu
Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.
Jaskanwal D S
JD
Sara
Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China.
Zhi Y
ZY
Cao
Department of Cardiology, Provincial Clinical Medical College of Fujian Medical University, Fuzhou, China.
Wei P
WP
Zheng
Department of TCM, Jing'An District Centre Hospital, Shanghai, China.
Tian S
TS
Zhang
Department of Epidemiology and Biostatistics, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine Peking Union Medical College, Beijing, China.
Hui J
HJ
Han
Key Laboratory of Trace Element Nutrition, Ministry of Health of China; National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention, Beijing, China.
Zhen Y
ZY
Yang
Department of Endocrinology, Quanzhou First Hospital, Fujian Medical University, Quanzhou, China.
Yi
Y
Zhang
Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
Fei L
FL
Wang
Department of Pharmacology, Beijing Anzhen Hospital, Beijing Institute of Heart Lung and Blood Vessel Diseases, Capital Medical University, Beijing, China.
Rui Y
RY
Pan
Department of Cardiology, Guangdong General Hospital, Southern Medical University, Guangzhou, China.
Jie L
JL
Huang
Department of Respiration, Zhujiang Hospital of Southern Medical University, Guangzhou, China.
Ling L
LL
Wu
Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, Beijing, China. zhangming2279@hotmail.com.
Ming
M
Zhang
Department of Otolaryngology Head & Neck Surgery, Beijing Anzhen Hospital, Capital Medical University, No.2, Anzhen Road, Chaoyang District, 100029, Beijing, China. weiyongxiang@vip.sina.com.
Yong X
YX
Wei
D002318:Cardiovascular Diseases / Q000453:epidemiology* / Q000401:mortality; D015331:Cohort Studies; D006801:Humans; D007037:Hypothyroidism / Q000453:epidemiology*; D008297:Male; D012307:Risk Factors; D016019:Survival Analysis
Cardiovascular events; Hypothyroidism; Meta-analysis; Mortality