Medical memo: Stress and chol... Health Article

Medical memo

The body's metabolism is complex — and despite major scientific advances, its fine print is still a bit hard to read. That's true even for a molecule as important as cholesterol. Researchers have learned that a man's blood cholesterol profile results from the interplay of many influences, including genetics, hormones, diet, body fat, exercise, and exposure to alcohol, tobacco, supplements, and medication. And a study from England suggests that this formidable list should be expanded further by adding stress.

A stressful study

The subjects were 106 male and 93 female British civil servants between the ages of 45 and 59. None had coronary artery disease or hypertension, and none was taking drugs for cholesterol or blood pressure. At the beginning of the study, each volunteer was weighed and measured, and each filled out a medical questionnaire. After blood samples were obtained, each subject was asked to perform a series of mentally stressful tasks while being monitored to evaluate their psychological and chemical responses. A final blood sample was obtained at the end of each experimental session.

Although there was considerable variation among the subjects, stress did produce an increase in blood cholesterol levels. On average, the total cholesterol rose about 7 mg/dl — the LDL ("bad") cholesterol by 5 mg/dl, and the HDL ("good") cholesterol by 1.6 mg/dl.

The increase in LDL cholesterol seems small, but if sustained, it would increase a person's heart attack risk by about 3%. But the rise in cholesterol occurred over a brief exposure to stress, and the scientists did not monitor blood tests later in the day to see if the levels stayed up. However, they did come back for a second look — three years later.

Second opinions

In terms of cholesterol, the passage of three years took more of a toll than a morning of experimental stress: Over three years, the volunteers' average cholesterol levels rose from 209 to 225 mg/dl, and the LDL cholesterol rose from 123 to 139 mg/dl. Changes in health habits did not account for the rise, but body weight did play a role; the people who gained the most weight experienced the greatest rise in their cholesterol levels. That was certainly expected. More surprising was the observation that the people whose cholesterol levels rose the most in response to stress also experienced the greatest three-year increases, even after body weight and other variables were taken into account.

Explanations and implications

The British experiment did not explore how stress affects cholesterol levels, but several possibilities come to mind. Stress activates the sympathetic nervous system and pumps stress hormones such as adrenaline and cortisol into the blood. Among other functions, the stress hormones act to mobilize the body's energy reserves. That means they liberate sugar from the liver and fatty acids from adipose tissue. These hormones also appear to boost the liver's production of low-density lipoproteins, which transport "bad" cholesterol in the blood.

The study showed that relatively mild mental stress can produce a relatively small rise in blood cholesterol levels. Unfortunately, the researchers did not learn how long the increase persisted. More research is needed, both to confirm the observation and to see if the stress-induced changes last long enough to be medically important.

The follow-up results are also interesting. Life is filled with stress. The people who responded to mild mental stress with the largest increase in blood cholesterol levels also showed the largest rise over the next three years. Weight gain and lifestyle changes did not explain this association. Perhaps, then, it is due to the cumulative effects of daily stress.

The metabolism is complex, and it will take time to sort out this latest wrinkle. Until scientists complete their work, you should do everything you can to help lower your cholesterol: eat right, get enough exercise, stay lean, avoid tobacco, don't abuse alcohol — and relax.