One of the objectives of the study is to determine the risk factors associated with hypertension among the study subjects. Obesity, family history of diabetes and hypertension were significantly associated with hypertension among the subjects (P <
0.05) while alcohol consumption (moderate and heavy) and cigarette smoking did not seem to be significant risk factors. The odds ratio, 95% confidence interval (CI) and significance of association of these factors are shown in table 12. The odd of developing hypertension was highest among patients with positive family history of hypertension followed by obesity.
5.5.1 Obesity
This study has shown a strong association between obesity and hypertension in the subjects (P<0.05) with 9 out of every 10 of the obese respondents being hypertensive (87.04%). The mean blood pressure of the obese hypertensives was significantly higher than the mean blood pressure of the overall hypertensive subjects, p < 0.05.
Similarly, the blood pressure showed a trend to increase as BMI increased, and mean BMI was significantly higher in hypertensive diabetics compared to normotensive diabetics, p < 0.05. Linear regression analysis showed a statistically significant relationship between BMI and hypertension in the study subjects. For each increase in kg/m2 in the BMI, the systolic and diastolic blood pressures are predicted to increase by 0.838mmHg and 0.366mmHg respectively.
The association between obesity, hypertension and diabetes has been the subject of much research. This study adds to the body of epidemiological evidence that shows a higher frequency of obesity in hypertensive diabetics to overall diabetics (35.61% versus 18.00%), a trend of consistent increase in frequency of hypertension with increasing BMI, and a significantly higher BMI in hypertensive diabetics in contrast to normotensive diabetics38. Dietary concerns have continued to play a key role in diabetes and hypertension, and although this study has shown a higher frequency of obesity in hypertensive diabetics, it should be noted that some studies have reported a relatively
low BMI in hypertensive diabetic patients which may be related to hypercatabolic state from hyperdynamic circulation associated with hypertension as well as restricted energy diet of these patients 71,75.
5.5.2 Family History of Diabetes
There is a positive family history of diabetes in 132 (44%) of the study subjects, majority of them (96.97%) being first-degree relatives. Evidence exists suggesting that DM has a genetic predisposition which is particularly strong in type II with first degree relatives having a much higher risk of developing the disease11,14.The findings in this study share this view and suggest that heredity plays a role in diabetes in Africans. This view is shared by other researchers and is not in agreement with earlier studies by Osuntokun et al who reported a family history of diabetes in only 2.4% of 832 subjects studied30,36.
Majority of the subjects with a positive family history of diabetes, (72.73%), were hypertensive with mean systolic and diastolic blood pressures significantly higher than the mean systolic and diastolic blood pressures of the overall hypertensive subjects in the study (p < 0.05).
From this study, there is an association between family history of diabetes and hypertension (p = 0.042). However, this association is weak with family history of hypertension having a stronger association (with hypertension) in the study subjects (p
= 0.002). This is similar to report from Mairiga’s study where family history of diabetes was found to have an association with the prevalence of hypertension in diabetics36.
Contrary to this study, however, this association was stronger than for family history of hypertension.
5.5.3 Family History of Hypertension
A quarter (25.33%) of the study subjects have a positive family history of hypertension with most of them (97.37%) occurring in first- degree relatives. Over three-quarters (77.63%) of the subjects with positive family history of hypertension are hypertensive.
Reports from existing literature indicate that genetics play a role in hypertension and epidemiological surveys in Africa have shown a strong association between family history of hypertension and the development of the disease59. This is supported by the frequent strong family history of hypertension or its complications in patients with hypertension59.
This study has shown a strong association between family history of hypertension and the prevalence of hypertension among the study subjects (p < 0.05). Of all the risk factors studied, this factor has the strongest risk for the occurrence of hypertension in the study subjects. Mairiga also reported a strong association between prevalence of hypertension and parental history of hypertension in his study36. Surprisingly most of the previous studies on diabetes, diabetic complications, and concomitant hypertension and diabetes were silent on this risk factor. More attention to it will aid in reducing the prevalence of hypertension in diabetics.
5.5.4 Alcohol and Cigarette Smoking
Alcohol consumption (moderate and heavy) and cigarette smoking (heavy) were not significantly related to hypertension in this study (P>0.05 in both conditions), and there is no significant difference between the mean systolic and diastolic blood pressure of the hypertensive subjects who smoke or take alcohol and that of the overall hypertensive diabetics.
Though heavy consumption of alcohol is clearly deleterious, studies have not reported it to be a risk factor towards the development of hypertension. It is reported to carry coronary risk11.
Smoking also carries acute cardiovascular effects and has recently been reported to be a risk factor for hypertension though the association is not fully understood59.
In a previous study, both alcohol consumption and cigarette smoking did not have association with hypertension in diabetics36.