A longitudinal study of blood pressure circadian rhythm from childhood to early adulthood.

Altered blood pressure (BP) circadian rhythmicity has been increasingly linked with cardiovascular risk. However, little is known about BP circadian rhythm change with age and its possible sociodemographic, anthropometric, and genetic moderators. Twenty-four-hour ambulatory BP was measured up to 16 times over a 23-year period in 339 European Americans (EAs) and 293 African Americans (AAs), with an average age of 15 years at the initial visit. BP circadian rhythms were indexed by amplitude and percent rhythm (a measure of rhythm integrity) and calculated using Fourier analysis. BP amplitude and percent rhythm increased with age and average BP (BP mesor). AAs were more likely to have lower BP amplitude and percent rhythm than their EA counterparts. BP amplitude and percent rhythm also decreased with adiposity (BMI and waist circumference). The summer season was associated with lower BP amplitude in AAs and lower percent rhythm in both AAs and EAs. Sex, height, socioeconomic status, physical activity, and family history of essential hypertension did not have an independent impact on BP amplitude or percent rhythm. The results of the present study suggest that BP circadian rhythm increases with age and BP mesor from childhood to young adulthood, decreases with adiposity, and that AAs are more likely to have lower circadian rhythm than EAs. Furthermore, we demonstrated that the summer season is associated with lower BP rhythmicity.