Sheri Colberg, PhD
A lot of my clinical research of late has been on a collision course with heart rate variability, or HRV for short. In fact, it has gotten to the point that I now believe that maintaining your HRV is the key to your well-being, longevity, and successful aging. Let me share with you some of the reasons why and what you can do to keep your HRV intact for longer.
For starters, we need to discuss what HRV represents. Your heart rate and its rhythm are largely under the control of the autonomic nervous system (ANS), which is comprised of the sympathetic and parasympathetic branches. It has long been known that the time between beats of the heart normally varies slightly (with inspiration and expiration, for example). Variations in heart rate may be evaluated by a number of methods, the simplest being time domain measures, although various spectral methods are also used.1 The important things to remember are that a loss of HRV can predict cardiovascular mortality and, in diabetes, is frequently associated with neuropathy of the ANS and that HRV normally declines slowly with advancing age anyway.
Why are changes in HRV such a big problem in diabetes? Although diabetic autonomic neuropathy rarely causes severe symptoms, it is strongly associated with at least a three-fold greater mortality risk.2,3 Specifically, cardiac autonomic neuropathy, frequently detected as a reduced HRV, has been associated with increased mortality in diabetes,2, 4, 5 cardiovascular disease,1 and aging.6 In fact, autonomic imbalances affecting sympathetic and parasympathetic nervous system function may be the strongest predictors of poor cardiovascular outcome and the risk of sudden death.2
Moreover, reduced HRV is associated with inflammation and is an early predictor of macrovascular disease, including carotid artery atherosclerosis.7 Cardiac autonomic imbalances are associated with adipose tissue inflammation in individuals with type 2 diabetes.8 Even before the onset of diabetes, those with postprandial spikes in blood glucose (that is, impaired glucose tolerance) have been shown to have significantly lower HRV.9 Parasympathetic (vagal) tone may decline further with autonomic imbalance, shifting toward a greater sympathetic drive during progression from a prediabetic state to type 2 diabetes.10
What can be done to preserve your HRV? Some research has shown that interventions designed to delay the onset of type 2 diabetes may be helpful. For instance, with lifestyle modification in the Diabetes Prevention Program, heart rate decreased and HRV increased in prediabetic individuals and were inversely associated with the development of diabetes regardless of weight change.11 Other strategies that target autonomic imbalance and inflammation may also have the potential to delay and/or prevent type 2 diabetes and its complications.12 In addition to therapeutic lifestyle changes, restoration of HRV has been demonstrated using increased physical activity, deep breathing, β-adrenergic blockers, aldose reductase inhibitors, ACE inhibitors, angiotensin receptor blockers, potent antioxidants like alpha-lipoic acid, and inhibitors of peroxynitrite formation.3
The activities that I am most interested in for maintaining HRV are physical activity, lifestyle interventions, and deep breathing. Physical activity can have a powerful effect given that it improves parasympathetic (vagal) tone, which is apparently the first thing to go with central nerve damage related to diabetes. Being physically active in any way possible on a regular basis is likely to have a very beneficial effect on maintaining a more normal HRV over time.
In addition, we recently finished a study looking at yogic breathing and found some benefit to HRV in people with type 2 diabetes, suggesting that taking some time out of your busy day to relax, breathe deeply, and destress may be an effective way to prevent declines. These findings also open the door to gaining benefits from alternate forms of physical activity, namely yoga, tai chi, and even just stretching. Just pick any activity you enjoy, and your HRV will likely benefit. What better reason do you need to increase your physical activity levels however you can?
- Electrophysiology TFotESoCatNASoPa. Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Circulation 1996;93:1043-65.
- Vinik AI, Maser RE, Ziegler D. Neuropathy: the crystal ball for cardiovascular disease? Diabetes Care 2010;33:1688-90.
- Vinik AI, Maser RE, Ziegler D. Autonomic imbalance: prophet of doom or scope for hope? Diabet Med 2011;28:643-51.
- Maser RE, Mitchell BD, Vinik AI, Freeman R. The association between cardiovascular autonomic neuropathy and mortality in individuals with diabetes: a meta-analysis. Diabetes Care 2003;26:1895-901.
- Ziegler D, Zentai CP, Perz S, et al. Prediction of mortality using measures of cardiac autonomic dysfunction in the diabetic and nondiabetic population: the MONICA/KORA Augsburg Cohort Study. Diabetes Care 2008;31:556-61.
- Beijers HJ, Ferreira I, Bravenboer B, et al. Microalbuminuria and cardiovascular autonomic dysfunction are independently associated with cardiovascular mortality: evidence for distinct pathways: the Hoorn Study. Diabetes Care 2009;32:1698-703.
- Gottsater A, Ahlgren AR, Taimour S, Sundkvist G. Decreased heart rate variability may predict the progression of carotid atherosclerosis in type 2 diabetes. Clin Auton Res 2006;16:228-34.
- Lieb DC, Parson HK, Mamikunian G, Vinik AI. Cardiac autonomic imbalance in newly diagnosed and established diabetes is associated with markers of adipose tissue inflammation. Exp Diabetes Res 2012;2012:878760.
- Diakakis GF, Parthenakis FI, Patrianakos AP, et al. Myocardial sympathetic innervation in patients with impaired glucose tolerance: relationship to subclinical inflammation. Cardiovasc Pathol 2008;17:172-7.
- Wu JS, Yang YC, Lin TS, et al. Epidemiological evidence of altered cardiac autonomic function in subjects with impaired glucose tolerance but not isolated impaired fasting glucose. J Clin Endocrinol Metab 2007;92:3885-9.
- Carnethon MR, Prineas RJ, Temprosa M, et al. The association among autonomic nervous system function, incident diabetes, and intervention arm in the Diabetes Prevention Program. Diabetes Care 2006;29:914-9.
- Cefalu WT, Richards RJ, Melendez-Ramirez LY. Redefining treatment success in type 2 diabetes mellitus: Comprehensive targeting of core defects. Cleve Clin J Med 2009;76 Suppl 5:S39-47.
Sign up for the Diabetes "Fit Brain, Fit Body!" fitness/lifestyle programs or for 5 free Healthy Living Reports at www.lifelongexercise.com, and access more articles and information at www.shericolberg.com. If you need tips for getting safely started on an exercise program, check out The 7 Step Diabetes Fitness Plan. For people with any type of diabetes who are already more active, consult the Diabetic Athlete’s Handbook.
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