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The blood pressure of American youngsters increased substantially during the 1990s, and weight gain seems only partially responsible, researchers said Tuesday.
Tulane University epidemiologists compared blood pressure statistics from two national surveys, one conducted between 1988 and 1994 and the other in 1999 and 2000. They said the readings increased for boys and girls between 8 and 17 years old and for African-Americans, Mexican-Americans and non-Hispanic whites.
Although the average increases were not the sort that would lead to actual illness among the young people surveyed, they are troubling because they herald future health problems, the researchers said.
In a separate study, scientists at the Medical College of Georgia found that high caffeine intake was associated with higher blood pressure among African-American teenagers.
The Georgia researchers compared the blood pressure of teenagers who consumed more than 100 milligrams of caffeine per day --- slightly more than in three sodas --- with that of a group consuming less than 100 milligrams per day.
The systolic blood pressure --- the measurement during a heartbeat --- of the first group averaged 119.3 millimeters of mercury compared with about 105 for the second group, the Georgia researchers reported in the Archives of Pediatrics & Adolescent Medicine.
"It's a dramatic increase," said Gregory Harshfield, a professor of pediatrics at the Georgia college.
The study, involving 159 teenagers, did not take into account other possible causes, and the researchers said caffeinated drink consumption may be an indication of other dietary and lifestyle practices that could drive up blood pressure. More study is needed, they said.
The Tulane study is being published today in the Journal of the American Medical Association.
Paul Muntner said he and his colleagues analyzed data collected in the National Health and Nutrition Examination Surveys conducted periodically by the National Center for Health Statistics, one of the Centers for Disease Control and Prevention. The surveys have been conducted since the 1970s.
Over all, the systolic blood pressure levels increased by an average of 1.4 millimeters of mercury, and the lower diastolic measurement --- taken when the heart is at rest --- increased by 3.3 millimeters of mercury.
The national average in the first survey was 104.6 over 58.4, and in the second survey was 106 over 61.7.
"We saw that only about one-third of the increase in systolic pressure was due to increased body weight," Muntner said in a telephone interview.
The health surveys apparently do not contain an explanation for increases in the 70 percent not explained by weight, he said. The group hypothesized that less physical activity and diet changes that can increase blood pressure without increasing weight may play roles.
Copyright 2004 The Atlanta Journal-Constitution