The Science of Stress
From gift shopping to party planning and visiting loved ones, the seemingly endless demands on time and the energy...
In the mid-20th century, endocrinologist Hans Selye coined the term “stress,” and described his theory that the chronic, unrelieved kind can cause disease. The idea that something ephemeral — an emotion — could have an impact on the physical was a radical idea at the time. Still, it came to be accepted.
What’s new today is that theory has become demonstrated fact. Advances in molecular biology and neuroscience not only prove that stress is a health hazard, but suggest that it can affect us more extensively than previously suspected — exacerbating conditions as varied as cardiovascular disease, asthma, arthritis, aging and more.
Stress harms our health in two basic ways. One is by leading us to fall into unhealthy habits such as sleeping poorly, exercising less, eating unhealthy foods and smoking. The American Heart Association reports that 20 per cent of Americans are worried that stress will affect their health — yet 36 per cent of them say they deal with stress by drinking alcohol or overeating.
Result: a self-fulfilling prophecy. The poor health habits that stem from stress account for an estimated two-thirds of the additional risk of heart attack and other cardiovascular illnesses in people with depression and anxiety found a 2008 study in the Journal of the American College of Cardiology.
The second way stress can harm us is through the endocrine, or hormone, system. Stress causes the brain to send a message to the adrenal glands to release the stress hormone cortisol. Cortisol helps the body recover from acute stress, including by raising blood sugar (the better to help you flee a sabre-toothed cat, for example).
The trouble comes when cortisol is released in response to background anxiety — and remains chronically elevated. High cortisol levels cause chronic inflammation, which can lead to arthritis and trigger the release of immune-system proteins called cytokines, implicated in such age-related diseases as Alzheimer’s, Parkinson’s and Type 2 diabetes.
Thanks to the very latest research, we now know that chronic worry can lead to:
• Cardiovascular disease: Stress increases blood levels of inflammatory molecules that promote the development of atherosclerosis (hardening of the arteries). These molecules also make the fatty arterial deposits called plaques more likely to rupture, causing a heart attack or stroke.
Stress also causes the nerves to flood the bloodstream with a molecule called neuropeptide Y (NPY), which raises heart rate and blood pressure. NPY stimulates the growth of abnormal smooth muscle in blood vessels, which leads them to become blocked with plaque-like deposits of microphages, thrombus and lipids. High levels of cortisol in the body are strong predictors that someone 65 or older will die of cardiovascular disease, scientist Nicole Vogelzangs of VU University Medical Center and colleagues found in a 2010 study.
• Impaired immune system: When stressed, the flood of NPY impairs the immune-system cells that fight infections. As a result, colds, flu and other viral diseases are more likely. So are virally caused malignancies such as cervical cancer.
• Faster weight gain: NPY also seems to be behind our tendency to overeat when we’re stressed. It throws a wrench into the brain’s appetite-regulation system and “unlocks’’ receptors in fat cells, stimulating them to grow in size and proliferate.
Early humans benefited from putting on fat in response to stress — which was of the “mammoths are scarce this year’’ variety rather than the “I can’t make my mortgage payment’’ kind. Now we put on a nice layer of fat that doesn’t actually help us cope with the source of our stress.
• Worsening of asthma symptoms: Asthma is marked by inflammation of the airways, so it’s no surprise that stress — by causing inflammation — increases asthma symptoms. A University of Wisconsin study showed how. When students with asthma inhaled an allergen (ragweed, dust mites or cat dander), lung inflammation was 27 per cent higher during finals than during a low-stress period — even though the allergen exposures were identical.
• High cholesterol: One reason stress can raise cholesterol levels may be because it encourages the body to produce more energy — to fight or flee — including fatty acids and glucose, both of which cause the liver to produce and secrete more LDL, or bad cholesterol.
• Increased risk of dementia: Stress in middle age can raise the risk of dementia, especially Alzheimer’s disease, in old age. Scientists at Sweden’s University of Gothenburg followed 1,400 women for 35 years, asking them about their levels of stress to see who developed dementia.
Women who reported repeated periods of stress in middle age were 65 per cent more likely to eventually develop dementia than women who did not. In women who reported stress at all time points, the risk was more than twice that of women who had escaped stress.
So what’s the connection? A solid body of research shows that stress hormones called glucocorticoids are toxic to neurons and to the synapses that connect them. The fewer synapses in a brain, the less of a cognitive cushion it apparently has after age-related mental decline sets in.
• Premature aging: Stress can reach into our very DNA, altering the “telomeres’’ that sit at the ends of chromosomes like the plastic tips at the end of shoelaces. Telomeres become shorter as the cell (and the person) ages. When enough telomeres reach a critically short length, the chromosome unravels like a shoelace that has lost its tip, and the cell stops dividing. This can trigger or contribute to age-related diseases. Scientists at Ohio State University found people under chronic stress have shorter telomeres and less of the enzyme telomerase, which repairs that damage.
If all this seems overwhelming, don’t stress out; as our understanding of stress has improved, so has the knowledge of how to fight back against the anxieties of everyday life. Aerobic exercise is an excellent place to start. Regular exercise, especially when combined with stress management training, can actually decrease cardiovascular risk in patients with heart disease.
The next step is to adopt principles of what’s known as cognitive behavourial therapy (CBT), including monitoring yourself for signs of stress and learning stress-management skills like deep breathing and spiritual development. In studies, people receiving cognitive behavourial therapy had a 41 per cent lower rate of both fatal and non-fatal heart events, 45 per cent fewer recurrent heart attacks and a 28 per cent lower rate of death over the eight years they were followed.
The bottom line: As science has uncovered more ways that stress can impair health, there is also increasing confidence that we can effectively keep chronic worry at bay. And that’s good news!
Dr Darius H Umrigar MD(AM)