Motivation
Hypertension and type 2 diabetes mellitus are common in the black population of South Africa.
The literature also shows that elevated blood glucose concentrations can lead to an increase in
blood pressure and a blunted decline in nocturnal blood pressure. Therefore, the motivation for
this study was to determine if blood glucose may play a role regarding the blunted nocturnal
decline in blood pressure in African and Caucasian men.
Aim
The aim of this study was to investigate the relationship between a blunted nocturnal decline in
blood pressure and blood glucose in African and Caucasian men.
Methodology
A comparative population study was preformed that consisted of 202 school teachers (101
African and 101 Caucasian) between the ages of 25–60 years from the North West Province,
South Africa. Subjects were excluded if their body temperature was elevated, had a
dependence or abuse of psychotropic substances, were regular blood donors and/or vaccinated
in the previous three months. Ambulatory systolic (SBP) and diastolic blood pressure (DBP)
were measured. Blood samples from the antebrachial vein were collected in sodium fluoride
tubes to determine the serum glucose level and glycosylated hemoglobin A1c (HbA1c)
percentage. Estimated average glucose (eAG) was determined from the percentage HbA1c by
means of a regression formula. Means and proportions were compared by standard t–test and
the chi–square test, respectively. Pearson correlations were used to determine unadjusted
associations and multiple regression analysis to determine adjusted associations between
variables.
Results and Conclusion
African men had an elevated HbA1c (p<0.001), eAG (p<0.001), nighttime SBP (p<0.001) and
DBP (p<0.001). These results remained similar when non–dipping African and Caucasian men
were compared. The Africans also smoked more (p=0.012), consumed more alcohol (p=0.049), had a higher percentage of non–dippers (p=0.054), HIV infected subjects (p<0.001) and a larger
number of subjects that used anti–hypertensive medication (p=0.049). The unadjusted analysis
showed positive correlations between all the blood pressure measurements and serum glucose,
HbA1c and eAG in the African non–dipper men. While in the non–dipper Caucasian men, only
daytime SBP and nighttime SBP (22:00–06:00) correlated positively with serum glucose, HbA1c
and eAG. Furthermore, when viewing the relationship between carotid intima–media thickness
(CIMT) and the blood pressure measurements in the African population, only nighttime (00:00–
04:00) SBP (r=0.581, p<0.001) and DBP (r=0.566, p<0.001) showed positive associations. After
adjustments were made for age and body mass index the associations between the various
blood pressure measurements and blood glucose disappeared in the non–dipper Caucasian
men. However, in the non–dipper African men both nighttime (22:00–06:00) SBP and (00:00–
04:00) SBP showed positive correlations with serum glucose, HbA1c and eAG. After full
adjustments (age, BMI, smoking, alcohol intake, physical activity, C–reactive protein and
baroreceptor sensitivity) were made, nighttime (00:00–04:00) SBP was the only measure of
blood pressure that correlated positively with HbA1c (p=0.069) and eAG (p<0.001) in the nondipper
African men. No significant relationships were found for Caucasian men. Furthermore, to
determine if the association between nighttime (00:00–04:00) SBP and eAG were independent
of CIMT, we adjusted for CIMT. By doing so the positive association between SBP and eAG
remained significant in the non–dipper African men (R2=0.617; =0.438; p=0.008) and nonsignificant
in the non–dipper Caucasian men (R2=0.423; =0.169; p=0.33). However, the
relationship between CIMT and eAG disappeared when we adjusted for SBP, suggesting that
the SBP and eAG relationship drives CIMT.
In conclusion, the association between the early morning SBP (00:00–04:00) and the blood
glucose in non–dipping African men suggests that the blunted decline in nocturnal blood
pressure during the early morning hours is associated with chronically elevated blood glucose. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2011.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/4649 |
| Date | January 2010 |
| Creators | Lammertyn, Leandi |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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