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Subclinical hypothyroidism increases CVD risk
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Adults with subclinical hypothyroidism are at increased risk for cardiovascular disease and all-cause mortality, and the link is amplified for those already predisposed to CVD, including those with diabetes, according to findings published in Thyroid.
“As screening for thyroid disease has become more common, the prevalence of [subclinical hypothyroidism] has been increasing in clinical settings,” Young Joo Park, MD, PhD, of the department of internal medicine at Seoul National University Hospital, South Korea, and colleagues wrote. “Therefore, evidence-based clarification about the influence of [subclinical hypothyroidism] on general health, specifically for mortality or morbidities such as CVD, is becoming increasingly important to assist screening or treatment of these conditions.”
Moon and colleagues performed a meta-analysis of studies published between 1990 and 2017 that addressed the connection between subclinical hypothyroidism and CV health. Among the 35 studies that involved 555,530 participants (n = 21,176 with subclinical hypothyroidism), 27 studies detailed the occurrence of fatal and nonfatal CVD events (n = 13,415). Twenty-nine studies with 532,332 individuals looked at all-cause mortality (n = 68,100 events) and found a greater risk for all-cause mortality among adults with subclinical hypothyroidism vs. those with euthyroid (RR = 1.2; 95% CI, 1.07-1.34).
The researchers also examined the data based on geography and found that participants with subclinical hypothyroidism in Asia and Europe had increased risk for CVD events (RR = 1.9; 95% CI, 1.5-2.4 and RR = 1.34; 95% CI, 1.03-1.74, respectively), whereas those in the U.S. had no elevated risk.
“This phenomenon might result from specific ethnic characteristics,” the researchers wrote. “However, it also might reflect possible confounding effects stemming from heterogeneity of the study population. All eight American studies were conducted with participants from the general population, whereas four of seven Asian studies and seven of 18 European studies were performed with participants at high CVD risk.
Prior risk for CVD was analyzed as well, with the researchers noting that for those already at high risk for CVD and all-cause mortality, subclinical hypothyroidism only exacerbated the issue (RR for CVD = 2.2; 95% CI, 1.28-3.77 and RR for all-cause mortality = 1.66; 95% CI, 1.41-1.94), particularly in comparison with those with low CVD risk (RR = 1.15; 95% CI, 1.06-1.22).
The researchers also examined how age affected the results. They found that younger participants (< 65 years) with subclinical hypothyroidism had an RR for a CV event of 1.54 (95% CI, 1.21-1.96) compared with older patients ( 65 years) who had an RR of 1.07 (95% CI, 0.97-1.18). Despite this finding, the researchers noted that among older adults ( 65 years) with CVD risk factors, subclinical hypothyroidism was linked to increased all-cause mortality (RR = 1.41; 95% CI, 1.08-1.85).
“Advancing age is associated with increased prevalence of [subclinical hypothyroidism], and around 10% of aged individuals have [subclinical hypothyroidism],” the researchers wrote. “[Subclinical hypothyroidism] is a possible contributor to diverse problems in aged individuals, such as CVD, cognitive dysfunction, musculoskeletal problem and deleterious effects on bone. However, because of a widening of the reference range for TSH with increasing age, the clinical significance of [subclinical hypothyroidism] in aged individuals is poorly understood.” – by Phil Neuffer
Disclosures: The authors report no relevant financial disclosures.
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