UWI’s Department of Tropical Medicine says that people of African origin have a high prevalence of hypertension, as well as high rates of hypertension related deaths from stroke, heart disease and renal failure. Studies in Caucasian populations have provided evidence that excessive secretion of cortisol may contribute to the development of hypertension. Cortisol is a hormone that is secreted from the adrenal glands, especially during periods of stress. Hypertensive African Americans have higher late-night and early morning salivary cortisol concentrations compared to persons with normal blood pressure. The research group previously showed that in Jamaican children, there were strong associations between morning cortisol concentrations and blood pressure.
According to the team, elevated early morning cortisol concentrations could be due to chronic psychosocial stress or genetic factors. Importantly, however, they could be a result of “fetal programming.” This phenomenon describes how growth within the womb and during infancy/childhood can influence someone’s metabolism, and thus their risk for chronic diseases in later life. In animal studies, high cortisol levels from the mother lead to the birth of growth-retarded offspring, who in turn secrete more cortisol throughout their life. These effects may persist over several generations. Although this mechanism is well described in animal models, it is as yet poorly described in humans.
However, mothers with elevated cortisol levels during pregnancy, especially if they are stressed, have growth retarded offspring. Other studies have shown that growth retarded babies have high cortisol secretion in childhood, and raised blood pressure in adulthood.
Afro-Caribbean populations
Afro-Caribbean populations have historically experienced high rates of poverty and have lower birth weights. They might therefore be expected to show evidence of the enhanced operation of this mechanism. UWI has therefore carried out a case-control study nested in an ongoing prospective cohort study of 569 mothers and children in Kingston. They then compared the cortisol levels of the mothers of 20 children with blood pressures at the upper end of the distribution with the cortisol levels of mothers of 20 children with blood pressures at the lower end. These children were not known to be growth retarded during pregnancy.Thereafter, the unit measured the cortisol levels in saliva of the children and theirmothers at 8 AM, 12 noon, 4 PM and 10 PM. Since blood pressure is strongly associated with the metabolic syndrome (i.e. type 2 diabetes, hypercholesterolaemia, obesity), as well as evaluated the mothers for the presence of the metabolic syndrome.
Results
Children with higher blood pressure were 390 grams lighter at birth and their morning cortisol levels were 76% higher than children with lower blood pressure. Their mothers also had morning cortisol levels that were 80% higher. There were no differences in fasting glucose, insulin, cholesterol, blood pressure or body fat between the two groups of mothers. There was a significant correlation of the cortisol levels in mothers and their children. Also, cortisol levels in the mothers were significantly associated with the children’s blood pressure. These associations were not affected by the mother’s socio-economic status. The team concluded thatAfro-Caribbean children with higher blood pressure have higher morning salivary cortisol levels. The children’s cortisol levels correlate significantly with the mother’s cortisol levels indicating a possible intrauterine origin. These findings suggest that the cortisol may play a role in the development of raised blood pressure in Afro-Caribbean people. These results raise interesting hypotheses on the origins of hypertension which need further investigation.
The Study was funded by The Caribbean Health Research Council provided the funds for this project. Members of the research team include Dr. Michael Boyne, Alexander Woollard, David Phillips, Carolyn Taylor-Bryan, Franklyn Bennett, Clive Osmond, Tamika Royal Thomas, Rainford Wilks and Terrence Forrester of the Tropical Medicine Research Institute, University of the West Indies, Mona, Jamaica and Medical Research Council Epidemiology Resource Centre (A.W., D.I.W.P., C.O.), University of Southampton, United Kingdom. (PR)
