Diabetes and subclinical hypothyroidism on heart rate variability

Abstract

Background: We aimed to analyse if the effects of coexistent diabetes and subclinical hypothyroidism extend to the cardio autonomic nervous system, using heart rate variability baseline data from the Brazilian Longitudinal Study of Adult Health. Materials and Methods: Heart rate variability analyses were performed by linear time and frequency domains in 5-minute time series collected in the supine position. The associations of diabetes and subclinical hypothyroidism with the lowest quartile group for heart rate and the highest quartile group for each heart rate variability parameter were analysed using additive and multiplicative terms in logistic models. For the first approach, the subsample was categorized into four groups: subjects without diabetes and normal thyroid function (controls); subjects without diabetes and subclinical hypothyroidism; patients with diabetes and normal thyroid function; and patients with diabetes and subclinical hypothyroidism. For the interaction alnalysis, diabetes and subclinical hypothyroidism diagnoses were included in separate, along with a multiplicative interaction term between them. Results: Point odds ratio estimates for the 4th quartiles of heart rate, and 1st quartiles of all heart rate variability measurements were higher for subjects with combined diabetes and subclinical hypothyroidism than for diabetes only, independently of main sociodemographic and clinical variables (HR: 8.33 vs 2.63; SDNN: 2.59 vs 1.61; RMSSD: 2.37 vs 1.42; LF: 2.83 vs 1.71; HF: 3.06 vs 1.39), but not independently of HbA1c and TSH. Only the interaction term for the association with heart rate, adjusted for sociodemographic and clinical variables, had borderline statistical significance. Conclusion: Diabetes and subclinical hypothyroidism exert a potential joint impact on cardiac autonomic control, showed by additive effects between diabetes and subclinical hypothyroidism, as well as a significant interaction term for the association with heart rate.

Cardiac Autonomic Modulation and Anti-Thyroid Peroxidase (TPO) Antibodies in Subclinical Hypothyroidism – Does Any Correlation Exist?

“…The LH-HF ratio is a sensitive marker of SVI [8]; hence, the increase in the LF-HF ratio represents considerable SVI in anti-TPOAb positive SCHypo. In the Poincaré indices (SD1 and SD2) of HRV, the width of SD1 reflects the parasympathetic modulation and the SD2 length reflects the sympathetic activity [14]. In our study, the SD1 value was profoundly decreased, and SD2 was increased in the antibody-positive SCHypo group than in controls, which can be used as a sensitive indicator of sympathovagal changes.…”

“…In anti-TPOAb positive SCHypo patients, a significant decrease in HFnu indicates decreased parasympathetic activity in these patients, as HFnu is an index of cardiac vagal drive [8,14]. This was supported by a significant reduction in TP of HRV in antibody-positive SCHypo patients compared with controls, like TP, in general, indicates the magnitude of vagal modulation of cardiac function [8,15].…”

Heart rate variability in hypothyroid patients: A systematic review and meta-analysis

“…The hypothalamus is involved in cardiac autonomic control and TSH release [ 60 , 61 ], linking the thyroid to the autonomic nervous system [ 62 , 63 ]. In hypothyroidism, the cardiac autonomic alteration may take place at an hypothalamic level [ 64 ]. Indeed, some studies suggested that TSH stimulates sympathetic output from the central nervous system and acts as a neurotransmitter, playing a critical role in determining sympathovagal imbalance [ 65 ].…”

An Update on Subclinical Hypothyroidism, Complications, and Its Management by Ayurvedic Medicines: A Review

“…In diabetes: Both diabetes and subclinical hypothyroidism exerted a combined impact on cardiac autonomic control and heart rate 31 . Postmenopausal women have been associated with a higher occurrence of subclinical hypothyroidism (SH) and the insulin resistance (IR) syndrome, which is related to type 2 diabetes mellitus, dyslipidaemia, and non-alcoholic fatty liver disease (NAFLD), hypertension in postmenopausal women, and obesity.…”