Cardiorespiratory fitness, cardiovascular reactivity, and twenty-four hour blood pressure in African-American women
Jackson, Erica Marie
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Hypertension is highly prevalent among Black women in the United States. Increased cardiovascular reactivity during stress and elevated blood pressure while sleeping have been reported in Blacks, and each is associated with hypertension risk and related negative health consequences. Though increased cardiorespiratory fitness is associated with hypertension risk reduction, studies of cardiovascular reactivity and diurnal blood pressure patterns among Black women have not examined the potential moderating effect of fitness. Cardiorespiratory fitness might reduce hypertension risk through an attenuation of stress reactivity or improved recovery after stress. A parental history of hypertension also has been associated with increased stress reactivity and altered 24-hour blood pressure patterns. This research was conducted to examine the effect of cardiorespiratory fitness on cardiovascular reactivity and recovery and on 24-hour ambulatory blood pressure in Black women with or without a parental history of hypertension. Participants were 30 normotensive women of low to moderate fitness level. Four standard laboratory stressors were performed while measures of heart rate, blood pressure, stroke volume, cardiac output, total peripheral resistance, calf blood flow, calf vascular resistance, and heart rate variability were obtained. Ambulatory blood pressure was monitored during a 24-hour period. Data were analyzed using multiple linear regression to determine the contribution of fitness, parental hypertension, and the fitness-by-family history interaction to the variance in dependent measures. Fitness was positively related to increased total peripheral resistance or calf vascular resistance during each stressor, and was associated with enhanced recovery of peripheral resistance and blood pressure after mental arithmetic. Otherwise, there was not a consistent effect of fitness across stressors. A parental history of hypertension was related to increased reactivity of heart rate variability components. A parental history of hypertension was associated with a blunted nocturnal decline of diastolic blood pressure, and fitness was not related to 24-hour blood pressure patterns or levels. Fitness generally was not associated with a reduction in stress reactivity in this sample, but was associated with enhanced recovery after selected stressors. Additionally, Black women with a parental history of hypertension have blunted nocturnal decline of blood pressure, despite having low blood pressure.