WASHINGTON, DC—A decade-long VA study following patients being treated for hypertension at 15 VA medical centers across the US has proven that, with enough effort, a hospital can make dramatic improvements in controlling patients’ blood pressure. And a recent examination of data from the study has shown that neither age nor gender factors into how well a patient’s blood pressure can be controlled. However, race remains a significant factor, as do the changing seasons—a phenomenon that researchers are still trying to understand.

Why BP Changes with the Seasons

U.S. Medicine first reported on the study three years ago when VA researchers released study data showing the vast improvements in hypertension control across all 15 VA hospitals. The study also newly revealed that blood pressure naturally rises and falls with the seasons, going up in the winter months and lowering in the summer. Continuing examination of this phenomenon has shown that, on average, hospitals reported a 7% rise in blood pressure during the winter, with the variation ranging from as high as 12% in some hospitals. Researchers are still trying to understand how and why this variation occurs.

At a presentation of the American Heart Association in November, VA researchers further revealed that this seasonal variation presents even more strongly in hypertensive patients. “People who are hypertensive are more [sensitive], and can be affected more by the seasonal change. People who are normal have some variation in blood pressure, but not to the extent of people that are hypertensive,” explained Dr Ross Fletcher, chief of staff at the Washington, DC, VAMC, and lead author of the study, in an interview. “We think it’s because of the sympathetic tone. When people’s pressures go up, they will have a response to that and they will fail to dilate their vessels. And they don’t have the same ability to modulate their blood pressure as a person with normal blood pressure.”

For example, a person with normal blood pressure can run and their blood pressure will rise, but eventually modulate itself. Aperson with hypertension, on the other hand, will run and their blood pressure will jump up and could remain elevated. Whatever causes the seasonal variation could have the same increased effect on hypertensive patients.

As for why the variation occurs, researchers have looked at weight as a possible factor. “Weight also increases in the winter.And for every pound of weight you gain, you will gain pressure.” However, the rise in weight during the winter and the rise in blood pressure do not seem to have a direct cause and effect relationship. “We don’t know whether the weight increase is the cause. We have seen the weight come up a little late. First the pressure goes up, and then the weight goes up. So, the relationship is uncertain.”

Exercise may also play a role. Exercise decreases in winter, and exercise has been shown to reduce blood pressure. This effect is entirely independent of any weight loss resulting from the exercise. What is known is that the seasonal variation has no correlation with the climate. Those VAMCs in cities with the coldest winters did not have the highest variation and those with the warmest winters did not have the smallest variation. “The variation is not the greatest in the most northern climates, and not the least in the most southern climates. San Juan, Puerto Rico, is pretty much in the middle, while Baltimore and Washington vary more than New York. It seems to have no relationship to latitude.”

Accounting for Seasonal Variation

Regardless of its cause, physicians need to take the effect into account when treating patients’ hypertension. “If there’s a 12% variation, then in the summer, you’ll be controlling 50% of your patients. Conversely, in the winter, you’ll be controlling 38%.”

However, physicians can take preemptive measures. If a patient has hypertension that is under control in the summer months, he or she should make an appointment to have it checked in the winter to make sure it has not gotten out of control. “If this happens, a change in medication should occur promptly until things are under control. We don’t have a problem controlling blood pressure in the winter if we know the problem is there.” Conversely, if a patient’s hypertension is under control during the winter, it might be controlled too well during the summer, and a reduction in medication should ensue.

Researchers must also keep this variation in mind when planning studies that have a blood pressure component. “If you’re doing a study and you started in November or December and you look at what you’re doing six months later, any intervention will have looked good. So, you have to carry your observation over to the following November or December.”

Of course, this requires physicians and researchers to be aware of the seasonal variation, knowledge of which Fletcher hopes will continue to spread through the medical literature. “We have presented it to the AHA. And it’s been disseminated [in leading periodicals]. I think people are becoming aware of it.”

The (Nonexistent) Gender Gap

When Fletcher and his colleagues looked at the data to see how gender affected blood pressure control, they were prepared to find differences between men and women. In some measures such as lipid lowering, there is a difference between males and females, with women not responding to treatment as well as men. VA researchers were wondering if they would see the same difference in blood pressure control. “There are some measures where gender makes a big difference, but hypertension is not one of them. The women, when they started off, seemed easier to control, but now they are the same.” The seasonal variation for men and women is also identical. “Initially, we thought we couldn’t look at gender. But when you look at half a million patients, 80,000 of them are women, and 80,000 is a big group.”

Age also plays little role in the ability of VA physicians to achieve hypertension control. While there was some disparity in ability to control blood pressure in older patients during the early years of the study, as VA improved its overall numbers, age became a non-issue. “Once we get past 2003, age makes no difference.”

Race, though, does remain a factor. It is generally harder to achieve hypertension control with African Americans than with other patient populations. “It’s well known that it’s harder to treat African Americans for hypertension than others. It may be that it’s a compliance problem, but I think that it’s a [genetic] difference. There are medications that will work in African American patients that don’t work in white populations.”

Fletcher presented hydralazine as one example—a smooth-muscle relaxant used to treat hypertension. In studies, hydralazine has shown to work better in African Americans than in white patients. VA studies on vasodilators showed that a combination of hydralazine and isosorbide dinitrate as a treatment for congestive heart failure worked well in African Americans where ACE inhibitors failed. A similar racially specific drug may someday be found specifically for hypertension, Fletcher posited.

VA has seen no similar difference with its Hispanic population. When the VA study started in 1999, Hispanics were ranked last in hypertension control. Over the years, they rose to become better controlled than Caucasians, though that might be due to a concentrated effort in that population. “I think that might be a local phenomenon. I think the people at the Puerto Rico VAMC got very tuned in for correcting hypertension and developed some mechanisms for doing that.”

The Goal of Perfect Control

The overreaching lesson from the VA data is that a concentrated and sustained effort by a hospital to control patient blood pressure will produce results. “Once you’re focused on controlling blood pressure in a given hospital, you can often make major changes. Even in our own hospital, we went up initially and then we leveled off for a while, or at least did not improve as dramatically for a while. Then we switched to a systematic approach where it was not just the primary care doctors giving care who were being asked to address hypertension, but the doctors in any clinic. And that is a huge difference.”

For example, a patient seeing a mental health specialist is likely to see that physician six times more frequently than their primary care doctor. If that specialist examines that patient’s blood pressure at every visit and treats it accordingly, then blood pressure control will occur much more rapidly than if the patient relies solely on their primary physician.

The VA’s electronic medical record has been a big help in this effort. The record is designed to provide a reminder to the physician to check the patient’s blood pressure if his or her last reading was high. “If you have focus and work at it, you can improve just about anybody. Sometimes it takes not just one drug, but two or three, or more in some cases. But if you are judiciously increasing step-wise the number of medications you need to control, control is possible. At the same time you are changing their lifestyle and encouraging exercise and changing diet.”

The challenge now is to maintain these levels of increased improvement. When the DC VAMC first began this systematic effort, levels of control rose to the 50% to 60% range and clinicians thought this was as good as things could get, Fletcher admitted. However, now the hospital finds itself moving into the 80% range, with the most severe hypertension (160/100) falling to around 3% of the patient population. And Fletcher has high hopes for the future. “I think we can get to the point where we are not only eliminating the 160/100, which is highly related to incidence of stroke, but we can eliminate the 140/90.”

As it is, he said, “We have a result that is hard to beat, and have set the benchmark for the country.”

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