Changes in kidney function appear to influence the occurrence of high blood pressure in individuals without overt kidney or cardiovascular disease, according to a report in the Annals of Internal Medicine.

The results suggest that early-stage kidney damage plays an important role in the development of high blood pressure, also referred to as hypertension, Dr. Bryan Kestenbaum, from the University of Washington in Seattle, and associates state.

The researchers evaluated the kidney function of 2,767 subjects who participated in the Multi-Ethnic Study of Atherosclerosis, a community-based study focusing on symptom-free cardiovascular disease. None of the subjects had hypertension, cardiovascular disease or symptoms of kidney disease when the study began.

The main outcome measure was the development of hypertension, defined as a blood pressure of at least 140/90 mm Hg, or the use of antihypertensive medications. Kestenbaum’s group also monitored levels of cystatin C, a blood protein filtered out of the blood by the kidneys that is commonly used as a measure of kidney function. High cystatin C levels after some heart attacks predict a poor patient outcome.

Nearly 20 percent of the subjects developed hypertension after an average of 3.1 years, the report indicates.

When the investigators analyzed the data, taking into account other factors that may have contributed to an increase in blood pressure, they found that for each 15-nmol/L rise in cystatin C levels, there was a 15-percent increase in the risk of developing hypertension.

By contrast, the subjects with the highest ratios of albumin-creatinine, which is also associated with irregular kidney function and a risk of cardiovascular disease, was not associated with an increased risk of hypertension when compared with those with the lowest levels.

While the findings suggest that variation in kidney function influences the risk of hypertension, the reason for such variation is unclear, the authors note.

Some explanations are that these individuals have been born with an abnormal number of nephrons, basic structure, or they were exposed early in life to heavy metals, such as lead, which both can cause kidney disease.

SOURCE: Annals of Internal Medicine. April 1, 2008.