LEGEND
LVH (2) LEFT VENTRICULAR HYPERTROPHY (Araoye criteria) LAE LEFT ATRIAL ENLARGEMENT
This study on prison population has been very fulfilling, as investigators had overlooked this significant section of our population, especially the assessment of their cardiovascular condition. This will probably explain the paucity of data on this subject.
AGE
The prison population comprised mainly of individuals in age ranges, 20 – 29 years and 30 – 39 year age categories. These age groups constitute 55.8 % and 24.8% of the total prison population respectively. Preponderance of these age categories in prison is probably due to youthful exuberance, lack of employment and the urge to breakthrough in life. These findings are in consonance with that of other studies in Nigerian prisons 14,44.
PRISON STATUS
Majority of male inmates (85%), and females inmates (81%) were awaiting trial, while only a small percentage 15% males and 19% female were convicted. Enquiries during the study revealed that the preponderance of unconvicted inmates was due to our cumbersome judicial system and poverty of the inmates leading to their inability to afford defense lawyers.
Studies in other Nigerian prisons also show similar pattern.14
WAIST CIRCUMFERENCE (WC)
Inmates had lower WC than controls due to poorer diet in prison, which is in consonance with other studies on prison inmates in Nigeria.14,44
These parameters are important in cardiovascular risk assessment. The abdominal (Android) form of obesity as opposed to hip-thigh (gynaecoid) obesity is strongly associated with dyslipidaemia45. Some anthropometric measurements may not distinguish between
overweight caused by excess body fat and overweight caused by excess musculature. WC is more useful than BMI in detecting central obesity, which is more relevant in cardiovascular risk assessment.46
BODY MASS INDEX (BMI)
The prison inmates were malnourished and markedly underweight. There were statistically significant differences between the BMI of the inmates and that of the controls. These differences were likely due to adverse living conditions and substandard feeding prevalent in the prison environment. Overcrowding in the prisons makes it difficult for the prison authorities to take adequate care of the inmates. These findings are corroborated by other studies on inmates in our environment22.
HIGH BLOOD PRESSURE. (HBP)
The SBP, DBP, MAP, and prevalence of HBP were higher among the inmates than controls.
The causes of these differences were most likely due to the stressful environment in which the inmates live, the increased prevalence of nephropathy due to poor diabetic control among the inmates and the lack of adequate medical attention. It will be necessary in further studies, to evaluate the role of salt and seasoning content of the poorly prepared prisoners’ diet on their BP elevation.
HBP can be precipitated especially in genetically susceptible individuals by adverse clinical, social and environmental conditions. Existing HBP can also be worsened by these same conditions. Imprisonment is a very stressful experience associated with anger, fear, agony, regrets and depression. In addition to these psychological stress, overcrowding, squalor and maltreatment by officials amount to physical stress.
The effect of stress on BP seen in this study was corroborated by other studies. Studies on Kalahari Bushmen, who left their traditional societies to become laborers, prison inmates, and factory menial workers, showed an elevated BP of 15 mmHg higher than their relatives at home.47 Sumbo warriors who joined Kenyan army also showed elevated BP48.
In the Kenyan Luo migration study,49 355 subjects who migrated from rural villages to Nairobi were followed prospectively for 2 years. As early as one month after migration, the distribution curve of BP had shifted to the right among migrants compared to their counterpart in the villages. The BP elevations were attributed to urban stress and increased salt intake.
Blacks have been shown to display greater cardiovascular reactivity to a number of physical and mental stressors than Whites. Blacks exhibited significant higher BP increase during video game challenge and cold pressor test than their White counterpart50,51,. Black children were found to have augmented pressor response compared to White children during isometric handgrip exercise and orthostatic testing52.
Based on these studies, repeated stress-induced sympathetic activation has been proposed to initiate a circle of increased vascular resistance and vascular hypertrophy that results in development of hypertension. Environmental stressors are likely to enhance sympathetic reactivity and to contribute to early development and severe progression of HBP in Blacks.
Progressive increase in BP with advancing age was also noted in this study. This pattern was evident in both inmates and controls. An increase in blood pressure with advancing age has been corroborated in other studies in both rural and urban populations in Nigeria.53,54
In this study, both male and female inmate showed marginally higher prevalence in LVH than their equivalent controls. However, there was no statistically significant difference. The higher prevalence of LVH among inmates was likely due to the higher prevalence of HBP.
The higher prevalence of LVH among hypertensives was also corroborated by Falase and Lawal57 who showed that moderate and severely hypertensives had significant left ventricular dilatation, myocardial hypertrophy and increased left ventricular mass. These findings were also corroborated by Onwubere et al.58
LVH by ECG and cardiomegaly by CXR were parameters used to access the effect of HBP on the heart. Although echocardiography-determined LVH is more sensitive especially on less severe LVH,55,56 ECG LVH was used, as it was not possible to take the inmates out for echocardiography.
Different LVH criteria have shown varied specificity and sensitivity.55 Romhilt Este’s point score and Sokolow Lyon’s criteria have sensitivity of 62.2% and 98.2% respectively. Their percentage false positivity are 3.3% and 53.1% respectively.
Araoye criteria, more tailored for Black population has sensitivity of 80.1% (males) and 77.0% in (females). False positivity is 8.2% (males), 10.6%(females). In this study, LVH by Sokolow and Lyon criteria showed slightly higher LVH prevalence 9.7% than Araoye’s 8.7%
among inmates and 7.8% vs 6.8% among controls suggesting that Sokolow and Lyon criteria have limitation of high positivity in Negroes.
LEFT ATRIAL ENLARGEMENT (LAE)
This study showed prevalence of LAE of 4.4% and 3.6% among male and female inmates respectively as against 4.4% and 2.9% among male and female controls respectively. LAE occur early in hypertensive disease, and it has been documented to occur even before LVH.
Studies have reported statistically higher prevalence of LAE among hypertensives.59
Biphasic P-wave in V1 is attributed to LAE in Caucasians. However, biphasic p-wave in V1 is common in normal Nigerian population. Araoye60 suggested that an actual increase in size of the negative component of the biphasic P-wave (>1mm) in lead V1 and a widened p-wave (> 0.12) with a notch >40msec in lead II are required for diagnosis of LAE in Blacks.
CARDIOTHORACIC RATIO (CTR)
In this study, 7.9% of male inmates and 6.5% of control met the criteria for cardiomegaly.
Among female study population, 7.3% of inmates and 5.8% of control also met the criteria for cardiomegaly. Normal CTR should be less than 50%, and heart size should be equal or less than 15.5cm61. Any value above these 2 parameters reflects cardiomegaly on CXR.
SERUM BIOCHEMISTRY
Higher prevalence of dyslipidaemia was found among the controls compared to the inmates.
The total cholesterol/HDL ratio was also found to be more deranged among the controls.
More individuals were found by this ratio to be dyslipidaemic than using individual lipid values. The higher prevalence of dyslipidaemia among the controls might be due to better feeding with the associated higher BMI. There was no significant statistical difference between inmates and control. Other studies that have been done to determine the level of total plasma cholesterol in Nigerians, found lower values in Nigerians when compared to Caucasians.45
Dyslipidaemia is linked to cardiovascular disease. High total cholesterol, high LDL, TG, and low HDL increase the risk of atherosclerotic complications of HBP. The multiple risk factor intervention trial (MRFIT),62 suggested that the risk of coronary artery disease is continuously graded, and bears a strong relationship to serum cholesterol concentration.
Creatinine profile among male inmates and control showed a progressive increase in levels with advancing age. HBP and glomerulonephritis were found to be the commonest causes of CKD at UCH Ibadan from 1961 – 1995.30 The risk of blood pressure related CKD appear to be especially high in Blacks independent of age, sex and prevalence of hypertension.31 In this study, the prevalence of elevated creatinine was higher among inmates than controls.
However, there was no significant statistical difference.
The findings in this study are in consonance with other studies which have found the risk of HBP- related CKD to be specially high in Blacks, independent of age, sex, and prevalence of HBP.31,63 Prevalence of elevated creatinine with increasing age was also observed in inmates and controls of both sexes.
FASTING BLOOD SUGAR (FBS)
The mean FBS of the inmates were slightly higher than that of their age matched controls. These differences although not statistically significant, are most likely due to poor DM controls within the prison confines.
Identification of DM among hypertensives is important as an associated clinical factor. This will affect the line of management in terms of choice of drugs, and target BP, since they have higher probability of CKD and Coronary artery disease.