To defeat high blood pressure or at least prevent its serious complication, we need more than the DASH diet and exercise. In this second article on hypertension, we address the role the nervous system plays in hypertension. To defeat hypertension or at the very minimum, control it successfully, we need to incorporate lifestyle strategies that help manage stress efficiently. However, there are many other lifestyle factors than stress that impact how your nerves control your blood pressure.
Sympathetic Nerves Yell “Fire!!!”
The nervous system helps to regulate the blood pressure through the sympathetic nervous system (SNS) which primes us for flight, fight, and fright. Under acute stress, the sympathetic nerves ratchet up their activity to help us cope with stress by shifting blood flow to the heart and muscles. SNS activity improves the ability of lungs to get oxygen, elevates blood sugar, dilates our pupils, and reduces our digestion. As concerning blood pressure, activation of the SNS speeds the heart rate and force of contraction, constricts the arteries, reduces blood flow to the kidneys—all of which cause the blood pressure to rise. In other words, the sympathetic nerves yell, “FIRE!” In contrast, parasympathetic activation slows the heart rate and promotes digestion. In hypertension, the tone of the sympathetic nerves is exaggerated or in overdrive. 1,2,3
Lifestyle Factors that Magnify Stress
Caffeine4,5 and nicotine6,7 amplify these effects of the sympathetic nerves. Just 250 milligrams of caffeine can increase plasma renin by 57%. Renin is an important enzyme involved in elevated blood pressure. The same amount also increases the stress hormones, norepinephrine and epinephrine, by 75% and 205% respectively, in healthy, young non-coffee drinkers who abstained from caffeine for three weeks prior to the blood tests.8 The actions of these two adrenal hormones mimic and reinforce the activation of the sympathetic nerves, although they work slower than the nervous system does.
Unfortunately, overeating, obesity,9 metabolic syndrome,10 diabetes,11 sleep deprivation,12,13 and fibromyalgia14 also increase sympathetic activity. What to do? Regular exercise, moderate salt restriction, and wise caloric restriction in obese individuals all decrease sympathetic activity. The good news is that wise dietary choices (including reasonable calorie restriction), moderate exercise, sufficient sleep of good quality, and genuine happiness can protect us from some of the detrimental effects that the sympathetic nervous system and stress, in general, have on our cardiovascular system.
Not Just the Sympathetic Nerves
Baroreceptors are sensory nerve endings that are stimulated by pressure changes in the walls of blood vessels. They monitor blood pressure and notify the brain to adjust it accordingly. The most sensitive baroreceptors are located in the aorta and in the right and left internal carotid arteries that supply blood to the brain.
A baroreceptor reflex, or bar reflex, is one of the body’s important mechanisms for keeping blood pressure within its normal limits. It provides an automatic negative feedback loop so that an elevated blood pressure reflexively initiates physiological activities that cause the blood pressure to decrease. Similarly, a low blood pressure also signals the brain. Then the brain, via the sympathetic nerves, initiates activities that cause the blood pressure to rise. In other words, the baroreflex promotes sympathetic inhibition if the blood pressure rises too high and sympathetic stimulation if the blood pressure falls too low.
Unfortunately, after two days of high blood pressure, the baroreceptors reset their “normal” point so that they consider the recent high blood pressure to now be normal. Baroreflex sensitivity refers to how well the baroreceptors work. In hypertension baroreflex sensitivity is diminished and is associated with increased mortality (particularly from sudden cardiac death) following myocardial infarction. Obesity,15 diabetes,16 smoking,17 sleep deprivation,18 and a high fat and refined carbohydrate diet are also lifestyle factors that can decrease baroreflex sensitivity. Fortunately, moderate exercise, 19,20 an optimal amount of sleep, wise calorie restriction,21 weight loss in obese individuals,22 consumption of cashews,23 and deep breathing all improve it.
Mental Health and Blood Pressure
Attitudes greatly influence blood pressure. For example, hostility and a high level of stress coupled with impatience make the risk for developing high blood pressure six to eight times greater.24
Chronic anxiety contributes to chronic activation of the sympathetic nerves. So do chronic stress, social isolation, and hostility. These conditions each contribute to increased sympathetic tone which means a faster heart rate, more vasoconstriction, and elevated blood pressure. These attitudes are especially detrimental in individuals with hypertension or diabetes because their SNS is already overstimulated.
According to Dr. Brian Curtis and Dr. James O’Keefe, Jr. in their article “Autonomic Tone as a Cardiovascular Risk Factor,” exercise, social support, faith, sleep, weight loss (if overweight), and smoking cessation improve the function of the autonomic nervous system so that there is less sympathetic influence and more parasympathetic influence.25 As a result, the risk for hypertension decreases and the chance of lowering elevated blood pressure increases.
Depression, in many cases, especially when accompanied with anger suppression and hostility, decreases baroreflex sensitivity.26,27 Depression is also associated with an elevated heart rate and stress hormones like norepinephrine. Unfortunately, depression, accompanied by anger suppression, high hostility, and anxiety, also reduces parasympathetic activity while increasing sympathetic activity. A history of major depression is a potent, independent risk factor for cardiovascular events.
Both chronic anxiety and hostility decrease baroreflex sensitivity. Studies show that women, but not men, with post-traumatic stress disorder have diminished baroreflex sensitivity.28 Dr. A. Steptoe and associates collected data from middle-aged men and women. They found that independent of age, socioeconomic status, smoking, body mass, and psychological distress, happy individuals had lower salivary cortisol both on working and nonworking days, reduced fibrinogen and stress responses, and in men, a lower ambulatory heart rate. Happiness was inversely related to ambulatory systolic blood pressure on follow-up. In other words, happiness can reduce the stress hormone cortisol and the risk for clotting, slow the heart rate, promote better nourishment of the heart muscle, and help to protect us from high blood pressure.29
Obviously, “As a man thinks in his heart, so is he.” Not only is this true spiritually and mentally, it is equally true physiologically.
So how can we reduce stress and be genuinely happy? Here are a few suggestions.
- Focus for a few minutes each day on the blessings you do have.
- Take at least 15 minutes each day to reflect upon the values and principles that you cherish. This author has found meditating on a principle or promise in the Bible to be especially helpful. Then choose your actions based on principles and not emotions! Actually, many stressors come from violating our principles.
- Distinguish between your real and imaginary stressors. I hate snakes even though they benefit the environment. Whenever I see one, I sweat profusely and feel my heart pounding (even when the snake is a stick!). Since an imaginary stressor can produce many of the same detrimental effects as a real stressor, we need to perceive things accurately.
- Add physical activity and moderate exercise to your daily life as they boost brain compounds that help us maintain a positive outlook.
- Cultivate a regular schedule that includes sufficient sleep. The heart muscle cells and certain cells in your arteries are influenced by circadian (daily) rhythm. So when these two necessities are neglected, the cardiovascular system is impacted negatively. A recent study showed that brain cells begin to die on an irregular schedule coupled with insufficient sleep!
- Learn how to breathe deeply and for a few minutes practice slow deep breathing every hour. Deep breathing stimulates the parasympathetic nervous system and has been shown to improve baroreflex sensitivity in obese children. To deep breath correctly, you must engage your diaphragm muscle. If you breathe in correctly, your diaphragm contracts, pushing your upper abdomen out. Diaphragmatic breathing may stimulate the vagus nerve. This nerve supplies approximately 75% of all parasympathetic nerve fibers. In contrast, rapid chest breathing stimulates the sympathetic nerves. To practice deep breathing, place a hand on your upper abdomen and as you inhale, make that hand rise.
For many articles on stress management and depression recovery, visit http://wildwoodhealth.com/blog/category/mental-health/
Disclaimer: The information in this article is helpful and is educational. It is not the author’s or authors’ or Wildwood Health Institute’s intent to substitute the blog article for diagnosis, counseling, or treatment by a qualified health professional.
Copyright through December 2023. All rights reserved by Wildwood Sanitarium, Inc.
- Curtis, B. and O’Keefe Jr, J., Autonomic Tone as a Cardiovascular Risk Factor. www.mayoproceedings.com.
- Julius, S., Effect of sympathetic overactivity on cardiovascular prognosis in hypertension. Eur Heart J, (19 Suppl F):F14-8, 1998.
- Julius, S. and Nesbitt, S., Sympathetic overactivity in hypertension. A moving target. Am J Hypertens, 9(11):113S-120S, 1996, review.
- Gupta, B.S., Caffeine and Behavior: Current Views and Research Trends, CRC Press, 1999.
- Corti, R., et al, Coffee acutely increases sympathetic nerve activity and blood pressure independently of caffeine content role of habitual versus nonhabitual drinking. Circulation, 106:2935, 2002.
- Shinozaki, N., et al, Cigarette smoking augments sympathetic nerve activity in patients with coronary heart disease. Int Heart J, 49(3):261-72, 2008.
- Anan, F., Smoking is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients. Eur J Clin Invest, 36(7):459-65, 2006.
- Robertson, D., et al, Effects of caffeine on plasma renin activity, catecholamines and blood pressure. New England Journal of Medicine, 298(4):181-186.
- Good, D., et al, Obesity, hypertension, and the heart. J Cardiometab Syndr, 3(3):168-72, 2008, review.
- Hall, E.J., Metabolic syndrome. The Journal of Health and Healing, 27(3):3-8.
- Track, C.J., et al, Effects of insulin on vascular tone and sympathetic nervous system in NIDDM. Diabetes January 1996 vol. 45 no. 1, 15-22.
- McEwen, B.S., Sleep deprivation as a neurobiologic and physiologic stressor: Allostasis and allostatic load. Metabolism, 55(10 Suppl 2):S20-3, 2006, review.
- Zhong, X., et al, Increased sympathetic and decreased parasympathetic cardiovascular modulation in normal humans with acute sleep deprivation. J Appl Physiol, 98(6):2024-32, 2005.
- Coaccioli S., et al, Fibromyalgia: nosography and therapeutic perspectives. Pain Pract, 8(3):190-201, 2008.
- Shrapari I., et al, Baroreflex function: determinants in healthy subjects and disturbances in diabetes, obesity and metabolic syndrome. Curr Diabetes Rev, 2(3):329-38, 2006.
- Ibid., Shrapari, I.
- Mancia, G., et al, Smoking impairs baroreflex sensitivity in humans. Am J Physiol, 273(3 Pt 2):H1555-60, 1997.
- Ogawa, Y., et al, Total sleep deprivation elevates blood pressure through arterial baroreflex resetting: a study with microneurographic technique. Sleep, 26(8):986-9, 2003.
- Komine, H., et al, Regular endurance exercise in young men increases arterial baroreflex sensitivity through neural alteration of baroreflex arc. J Appl Physiol, Mar 19, 2009.
- Ueno, L.M. and Moritani, T., Effects of long-term exercise training on cardiac autonomic nervous activities and baroreflex sensitivity. Eur J Appl Physiol, 89(2):109-14, 2003.
- Thomas, J., et al, Long-term caloric restriction improves baroreflex sensitivity in aging Fischer 344 rats. J Gerontol, 48(4):B151-5, 1993.
- Alvarez, G.E., Weight loss increases cardiovagal baroreflex function in obese young and older men. Am J Physiol Endocrinol Metab, 289(4):E665, 2005.
- Schutte, A.E., et al, Modulation of baroreflex sensitivity by walnuts versus cashew nuts in subjects with metabolic syndrome. Am J Hypertens, 19(6):629-36, 2006.
- National Institute of Health NHLBI study finds, hostility, impatience increase hypertension risk. Impatience and hostility–two hallmarks of the “type A” behavior pattern–increase young, www.nhlbi.nih.gov/new/press/03-10-21.htm.
- Curtis, B.M. and O’Keefe Jr., J.H., Autonomic tone as a cardiovascular risk factor: the dangers of chronic fight or flight. Mayo Clin Proc, 77(1):45-54, 2002.
- Broadley, A.J., et al, Baroreflex sensitivity is reduced in depression. Psychosom Med, 67(4):648-51, 2005.
- Hughes, J.W., et al, Baroreceptor sensitivity at rest and during stress in women with posttraumatic stress disorder or major depressive disorder. J Trauma Stress, 20(5):667-76, 2007.
- Steptoe, A. and Wardle, J., Positive affect and biological function in everyday life. Neurobiol Aging, 26(Suppl 1):108-12, epub Oct 6, 2005, review.
- Steptoe A. Positive affect and health-related neuroendocrine, cardiovascular, and inflammatory processes. Proc Natl Acad Sci U S A. 2005 May 3;102(18):6508-12.