Abstract
This study tested the hypothesis that an 8-week exercise intervention supported by mobile health (mHealth) technology would improve metabolic syndrome (MetS) risk factors and heart rate variability (HRV) in a population with MetS risk factors. Participants (n = 12; three male; aged 56.9 ± 7.0 years) reported to the laboratory for assessment of MetS risk factors and fitness (VO2max) at baseline (V 0) and after 8-weeks (V 2) of intervention. Participants received an individualized exercise prescription and a mHealth technology kit for remote monitoring of blood pressure (BP), blood glucose, physical activity, and body weight via smartphone. Participants underwent 24-h ambulatory monitoring of R–R intervals following V 0 and V 2. Low and high frequency powers of HRV were assessed from the recording and the ratio of low-to-high frequency powers and low and high frequency powers in normalized units were calculated. One-way repeated measures analysis of variance showed that waist circumference (V 0: 113.1 ± 11.0 cm, V 2: 108.1 ± 14.7 cm; p = 0.004) and diastolic BP (V 0: 81 ± 6 mmHg, V 2: 76 ± 11 mmHg; p = 0.04) were reduced and VO2max increased (V 0: 31.3 ml/kg/min, V 2: 34.8 ml/kg/min; p = 0.02) with no changes in other MetS risk factors. Low and high frequency powers in normalized units were reduced (V 0: 75.5 ± 12.0, V 2: 72.0 ± 12.1; p = 0.03) and increased (V 0: 24.5 ± 12.0, V 2: 28.0 ± 12.1; p = 0.03), respectively, with no other changes in HRV. Over the intervention period, changes in systolic BP were correlated negatively with the changes in R–R interval (r = −0.600; p = 0.04) and positively with the changes in heart rate (r = 0.611; p = 0.03), with no other associations between MetS risk factors and HRV parameters. Thus, this 8-week mHealth supported exercise intervention improved MetS risk factors and HRV parameters, but only changes in systolic BP were associated with improved autonomic function.
Highlights
Cardiovascular diseases are the leading cause of death world-wide accounting for 48% of mortality from non-communicable diseases [1]
This paper reports on a subset of participants with sufficient data for assessment of Heart rate variability (HRV) in a population presenting with Metabolic syndrome (MetS) risk factors
Participants were included if they had at least two MetS risk factors according to ATPIII guidelines: waist circumference ≥88 cm or 102 cm; resting systolic blood pressure (SBP) ≥135 mmHg and/or diastolic blood pressure (DBP) ≥85 mmHg; fasting plasma glucose ≥6.1 mmol/L; triglycerides ≥1.7 mmol/L; and high density lipoprotein cholesterol (HDL) ≤1.03 mmol/L or 1.29 mmol/L [National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) [17]]
Summary
Cardiovascular diseases are the leading cause of death world-wide accounting for 48% of mortality from non-communicable diseases [1]. Type 2 diabetes mellitus is an independent risk factor for cardiovascular diseases and cardiovascular complications are common in this patient population. Metabolic syndrome (MetS) is a clustering of risk factors including abdominal obesity, hypertension, dysglycemia, and dyslipidemia, which doubles the 5-year risk of developing cardiovascular diseases and increases the life-time risk of developing type 2 diabetes mellitus fivefold [2]. Diminished HRV predicts all cause and cardiovascular mortality [5,6,7,8] and impaired autonomic function may be especially dangerous for those with an already increased risk of developing cardiovascular disease. Patients with type 2 diabetes mellitus with low HRV have double the risk of mortality compared to those with normal HRV [5]. There is evidence that lifestyle changes may have positive autonomic effects [13, 14] but, it is unknown whether changes in MetS risk factors with lifestyle modifications are associated with concomitant changes in HRV
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