Low levels of fitness in young adults may account for a substantial proportion of hypertension incidence, researchers report in the journal Hypertension.
Their findings "show that fitness during young adulthood – a time when cardiovascular disease risk factor burden is typically low – is an important indicator of hypertension development in middle age," said lead author Mercedes Carnethon (Northwestern University, Chicago, Illinois, USA). The team evaluated the associations between fitness and physical activity and 20-year incidence of hypertension among 4618 participants in the CARDIA (Coronary Artery Risk Development in Young Adults) Study. The participants were aged 25 years on average and free of hypertension at baseline. Their fitness was estimated from the duration of a symptom-limited graded exercise treadmill test, while physical activity was self-reported. Over 20 years, 1022 participants developed hypertension at a rate of 13.8 per 1000 person-years. Both baseline fitness, at a hazard ratio of 0.63 per 2.9-minute increment, and physical activity, at a hazard ratio of 0.86 per 297 higher exercise units, were inversely associated with incident hypertension, after adjusting for a broad range of risk factors including age, gender, race, baseline smoking status, systolic blood pressure, alcohol intake, dietary sodium and fibre intake, cholesterol, and body-mass index. The association of hypertension with fitness was stronger than with physical activity, being similar across tertiles of physical activity. By contrast, the association between physical activity and hypertension was strongest among participants in the highest tertile of baseline fitness, at a hazard ratio of 0.80. The researchers estimated that, overall, 34% of hypertension could be prevented if participants moved to a higher fitness category. "In conclusion, low fitness demonstrates a more robust association with the development of hypertension than low self-reported physical activity, yet the two appear to exert independent effects," Carnethon et al write. "Although the population burden of hypertension attributable to low fitness and activity varies across sex and age groups, the contributions are meaningful and suggest a plausible target for intervention to lower hypertension rates in the population," they observe. Read the abstract
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