Non-communicable diseases such as obesity, diabetes and cardiovascular disorders
have been traditionally associated with developed countries. However, in recent
decades the prevalence of these diseases and their antecedent risk factors has
rapidly increased in developing countries (Boutayeb and
Boutayeb, 2005). These changes are caused to a large extent by dietary changes
in relation to socio-economic and living environmental conditions (Svetkey
et al., 2001).
Hypertension is a very prevalent condition in industrialized countries and
has varied prevalence in developing countries. It is associated with the incidence
of some diet-related non-communicable diseases such as stroke and coronary heart
diseases (Williams, 1994). Although the actual cause of
hypertension is unknown, obesity and genetic factors predispose certain individuals
to high blood pressure (Michael, 1997). Dietary approaches
to hypertension are under investigation. However, certain dietary alterations
lead to a modification of cholesterol levels and a reduction in cardiac risk.
The use of a strictly vegetarian and very-low-fat diet reduced serum cholesterol
level by 11% and blood pressure by 6% within 12 days (McDougall
et al., 1995). Less restrictive diets that contain lean meat, fruits
and vegetables and have a high ratio of polyunsaturated fat to saturated fat
are beneficial to the control of diet-related non-communicable diseases. Healthy
lifestyles, which help to increase an individual sense of well being, can prevent
illness (Pickering, 2006). These include eating a balanced
diet, regular physical exercise, reducing stress, and avoiding abuse of alcohol
Globally, unhealthy eating habits and physical inactivity are responsible for
at least 300,000 deaths each year. For example, 39% of all deaths in 1998 were
due to diseases associated with diet. Also, the three most important personal
habits that influence health include smoking, alcohol abuse and diet (WHO,
1998). Lifestyle interventions have been identified to reduce the occurrence
of hypertension among persons with family history of hypertension and may also
reduce the risk of cardiovascular events (Zellner and Sudhir,
1996). Studies have provided evidence of the beneficial effects of lifestyle
intervention on blood pressure and serum lipid levels (Elmer
et al., 1995). Furthermore, it has been recommended that for the
treatment of high blood pressure physicians should encourage patients to make
lifestyle changes their priority (Frohlich, 1995). Sedentary
lifestyle is strongly associated with increased mortality from coronary artery
disease (Yeager et al., 1995) and may be a risk
factor for hypertension (Miller et al., 1999).
Exercise alone can lower blood pressure, and when combined with weight reduction
it reduces blood pressure substantially (Miller et al.,
A relationship has been found between occupational stress and high blood pressure
(Ramsay et al., 2006). Studies also showed a
reduction of 6 to 26 mmHg in systolic blood pressure and a reduction of 5 to
15 mmHg in diastolic blood pressure when stress-management techniques were used.
Many people become hypertensive because of excessive alcohol intake. Besides,
with a reduction of alcohol intake, 5 mmHg decline in systolic blood pressure
and 3 mmHg decline in diastolic blood pressure have been reported. Moreover,
when reduction of alcohol intake is combined with weight loss, blood pressure
reduces by up to 10 mmHg in systolic blood pressure and 7.5 mmHg in diastolic
pressure (Stevens et al., 2001).
The research was conducted to generate data on the associations between characteristics of underground miners, their nutrition and blood pressure.
MATERIALS AND METHODS
Study design, population and area of study: The study was cross-sectional, involving male miners in the Obuasi municipality in the Ashanti Region of Ghana. The study was conducted between April 2006 and November 2007. There are about 6,474 people employed as underground miners in the municipality. The municipality is noted for mining and trading as the main economic activity. Senior and junior staffs who work underground in the municipality were chosen for the study.
Sample size determination: Using a 95% confidence interval, a prevalence
of hypertension (28.7%) in the Ashanti Region of Ghana (Cappuccio
et al., 2004; Bahram et al., 2001) percent
error (d) of 5% then the required sample size for the study was 314 but was
approximated to 320 to improve the precision of the estimates (Appendix
Eligibility criteria: An underground male miner officially registered as an employee of AngloGold Ashanti who is healthy, resides in AngloGold Ashanti residential facility and consented to be part of the study were included.
Sampling technique: The selection of the subjects for the study was done using cluster method. The clusters were divided into senior and junior staff Residential Areas (RAs) respectively. With the help of simple random sampling procedure 16 RAs out of 24 RAs in the Obuasi municipality identified by AngloGold Ashanti estate department as the official RAs of miners were randomly selected. This was done by writing the names of the RAs on pieces of paper using balloting technique. RAs for the study were picked randomly. 7 and 9 RAs were randomly selected for both senior and junior staffs respectively. The RAs where the study was conducted include Anyinam (RA), Bruno (RA), Biney (RA), Dankwa (RA), Monsey Valley (RA), Tiny Rowland (RA) and Rains Hill (RA) for the senior staffs. Those of the junior staff were Anyinam quarters, Bidieso quarters, pompora quarters, Kwabrafoso quarters, wawase, quarters Sam Jonah estate, Biney Security Barracks quarters, ToyTown quarters and Security Barracks quarters.
Weighting technique was also employed for the determination of the number of houses needed in each RA to be selected for the study. This was done to avoid biases during the selection of houses in each RA for the study. Knowing the number of houses needed in each RA, house numbers were written on pieces of paper and then trough the use of lottery technique houses were randomly identified for the interview of house hold index Figures (underground male miners).
Permission for the study: Permission was sought from AngloGold Ashanti,
the Municipal assembly and the Municipal Health Directorate of the Ghana Health
Service, Obuasi. Furthermore, those who consented to be part of the study signed
a consent form (Appendix 2) and those who could not sign thumb
printed to show consent.
Pre-testing of questionnaire: Instruments for the study were pre-tested on workers of Mining and Building Contractors (MBC) Obuasi. The workers have similar characteristics as those of the underground male miners at obuasi. This was done purposely to ensure the clarity of the questionnaire and the efficiency of study instruments.
Research instruments: The research instruments used were questionnaire
(Appendix 3) electronic digital sphygmomanometer, UNI SECA
scale, SECAMicrotoise, tape measure and Harpenden skin fold caliper.
Data collection and measurements: A semi-structured questionnaire was
used to obtain information on the demography of the study participants (age,
number of years worked at the mine, marital status religion etc.), socio-economic
status (income at the end of the month, properties owned by respondents etc.),
lifestyle variables (smoking status, alcohol usage, 24 h physical activity questionnaire
adopted from (Jimaina and Van, 2001), morbidity of the
study participants (hypertension and diabetes) as well as nutritional body composition
(Percent Body fat, Skin fold thickness and Body Mass Index etc.) Dietary and
eating habits were assessed using food frequency questionnaire and two day 24
h dietary recalls. Descriptive statistics for anthropometric variable are shown
in Table 1.
|| Descriptive statistics anthropometry and hypertension status
|*p-value significant at<0.05 (Independent sample t-test)
as shown in Table 1 almost all the anthropometric variables
showed a significant association between the means of hypertensive and nonhypertensive
respondents as well as that of the systolic and diastolic blood pressure
Height: The height of subjects were taken with SECA microtoise to
the nearest 0.1 cm. Measurements were taken with subjects standing upright,
bare footed, buttocks, calf, back, head and shoulder blades touching a smooth
vertical wall. Subjects were positioned such that Frankfurt plane was observed.
Subjects were made to breath-in and the measurement recorded in centimeters.
Weight: Measurements of weight of respondents were taken with respondents standing upright and the eye perpendicular to the height. They were bare-footed, in minimum clothing and without any objects on them UNI SECA Scale calibrated in Kg with a least count of 0.1 kg was used in taking the measurements.
Body mass index: The BM1 as a derived quantity of weight and height was determined by dividing weight in kilograms by the height in meters squared.
Skin fold thickness measurement
Triceps: Subjects were made to relax their arm while the arm hangs. The
skin and sub- cutaneous tissue were grasped 1cm above the arms midpoint (between
the tip of the acromial process of the scapula and the olecranon process of
the ulna). The fold runs parallel to the long axis of the arm while measurements
were taken at the posterior midline (Tam et al.,
Biceps: The subjects arms were made to hang relaxed at the side.
The anterior aspects of the upper arm skin fold were lifted directly above the
centers of the cubital fossa. Measurements were taken at the same level as that
of the triceps skin fold (Tam et al., 1999).
Sub scapular: With the shoulder and the arm relaxed 1 cm of the skin
was lifted under the inferior angle of the scapular. The fold runs parallel
to the natural cleavage lines of the skin before measurements were made (Tam
et al., 1999).
Suprailiac: About 2 cm of the skin fold of the subjects were lifted
above the iliac crest in the midaxillary line. Measurements were then taken.
All the measurements were in duplicate and the average value taken as the skin
fold measure. Using harpenden skin fold caliper measurements were taken to the
nearest 0.2 mm on the left side of the body (Tam et al.,
Waist-to-Hip Ratio (WHR): Waist and Hip circumference were measured
with subjects standing with feet together and in gentle expiration (WHO,
1995). Waist circumference was measured with a tape measure encircling the
body horizontally at the umbilicus. The hip circumference was also measured
at the level of maximal circumference in the hip region while they stood erect
and with feet together. The waist-to-hip ratio was calculated by dividing the
waist circumference by the hip circumference (Seidell et
Dietary intake assessment
Food frequency questionnaire: Structured questionnaire with the list
of Ghanaian foods were used to determine the frequency with which the study
participants consume them. Subjects were made to tell the number of times they
have eaten any of the food prepared from the Ghanaian food groups within the
24 h dietary recall: Two day twenty-four hour dietary recalls (one week
day and one weekend) were performed. The subjects were made to recall all foods
and beverages consumed during the previous day noting the nature and amount
of each item. Serving sizes were estimated with standard sized cups, bowls and
spoons. Simple food models in pictorial form were used to quantify the reported
food intake (Williams, 1994).
Blood pressure determination: Electronic digital sphygmomanometer was used to measure the blood pressure of the subjects on their left arm. Two blood pressure measurements were taken first before the questionnaire administration and other study measurements. The mean of the two blood pressure readings were recorded and taken as the blood pressure values for each study participants after they have rested for at least 5 min time interval before the second pressure measurements.
Data analysis: The data were entered and analyzed using Statistical Package for Social Sciences (SPSS version, 13.0). ESHA version 6.02 nutrient database was also used to analyze nutrient content of estimated food intake for the 24 h recall dietary survey. Means standard deviation and ranges were calculated for continuous variables while proportions were presented for categorical variables. Chi-square, independent sample t-test, correlation were used to determine the association between blood pressure, background characteristics, anthropometric indicators and lifestyle variables. Logistic regression was used to determine the extent to which significant variables predicted high blood pressure
RESULTS AND DISCUSSION
Body composition and blood pressure:As shown in Table 2, 127; 39.7% of the respondents had BMI within the range 25.0-29.9 kg m-2. A total of 198; 61.9% overweight and obese cases were identified. About 122; 38.1% normal BMI respondents were observed. About 150; 46.9% of the respondents had a WHR ≥ 1.0 and 170; 53.1% had WHR<1.0. About 170; 53.1% of the respondents had their percent body fat within the normal range of 10-25%. Body mass index, waist-to-hip ratio and percent body fat were significant with blood pressure (p<0.05).
|| Body composition in relation to blood pressure (N=320)
|p-value significant at <0.05 (Chi-square test); 1Body
Mass Index (kg m-2); <18.5 thin, 18.5-24.9 normal, 25.0-29.9
overweight; 2WHR (Waist Hip Ratio) Male (<1.0 normal, ≥
1.0 bove normal) 3Normal body fat (%): 10-25%
There was an association existed between body mass index, waist-hip circumference
ratio and percentage body fat. This confirms a study conducted by Jimaina
and Van (2001) where similar findings were recorded in a cross-sectional
study. In addition being obese or overweight had about 3-4 times risk for developing
hypertension as compared to having normal body weight. This finding is consistent
with Ramsay et al. (2006) where body mass index,
waist circumference and fat mass index were associated with the prevalence of
cardiovascular disease among 4,252 British men in a cross-sectional study.
A total of 61.9% overweight and obese cases were found in this study. This
high prevalence of obesity and overweight cases recorded suggests the lack of
nutritional awareness and understanding among the respondents. It also implies
that, the majority of people still accept the notion that big is beautiful,
which emphasizes hierarchy and status in communities (Jimaina
and Van, 2001). The prevalence of obesity and overweight and its corresponding
high hypertensive cases can be linked to overweight and obesity being associated
with hypertension, metabolic syndrome, elevated blood lipid, diabetes mellitus
and dyslipidemia (Harris et al., 2000; Doll
et al., 2002). The high rate of central obesity (46.9%) and percent
body fat (46.9%) recorded in this study suggests a potentially high risk for
the development of diabetes, heart disease and hyperlipedemia (Doll
et al., 2002).
Nutrient intake and blood pressure: Correlation matrix analysis was
conducted to evaluate the relationship between blood pressure and nutrient intake
(Table 4). The study indicated that only potassium correlated
significantly with both systolic and diastolic blood pressure. This finding
is in agreement with Vogt et al. (1999) meta-analysis
that suggested that, potassium lowers systolic and diastolic pressure particularly
among people with high sodium intake. Also, according to LaRosa
et al. (1999) diet rich in low fat and high in potassium, magnesium
and calcium decreases blood pressure substantially and has a greater effect
than reductions in sodium intake; but in this study, only potassium intake supported
LaRosa et al. (1999) findings, this is likely
to be attributed to the study being cross-sectional and again, the possibility
that, the intakes of magnesium and calcium as a mineral nutrients by the study
subjects not being enough to correlate with systolic and diastolic blood pressure
discovered that, fiber intake failed to correlate significantly with systolic
and diastolic blood pressure.
|| Average nutrient intakes of hypertensive and non-hypertensive
|Independent t-test (p = 0.05) shows no significant difference
in the mean nutrient intake of hypertensive and non-hypertensive. However,
the mean intakes of nutrients among the hypertensive were higher than that
of the non- hypertensive
This finding is consistent with other studies conducted to determine the effect
of dietary fiber on blood pressure where inconsistent results were obtained
(Vogt et al., 1999).
Independent sample t-test was used to evaluate the differences between the means of nutrient intakes of hypertensive and non-hypertensive subjects (Table 3) but it was realized that, no significant association were obtained between the nutrient intakes in the two groups. This result demonstrates the fact that the nutrients consumed by the two groups are completely different with regards to their average nutrient intakes, with hypertensive consuming higher average nutrients. This finding indicates lack of knowledge on the health consequences associated with excessive nutrient intake among the study subjects.
Age and blood pressure: The research showed a significant association between age (years) and blood pressure. Besides, from the logistic regression analysis (Table 5) it was evident that, the risk of developing hypertension increased as the age of the respondents increased.
Respondents aged 50-59 years had about 8 times risk of developing hypertension
compared to those aged 20-29 years. This confirms the Framingham study that
found that, blood pressure rises as one ages (Steven and James,
1988). Also, according to Steven and James (1988)
diastolic blood pressure peaks and falls as one ages, but systolic blood pressure
tend to rise linearly with age throughout adult life.
The results support Steven and James (1988) study that
showed that, for all men, the prevalence rate of hypertension doubles from 28.4%
in the 35-44 year range to 60.2% in the 65-74 year range. This finding can be
as a result of the fact that, as one ages there is a decrease in compliance
and an increase in rigidity of the aorta and its major tributaries. The aorta
becomes increasingly rigid with thickening of the arterial intima and media.
These layers of the vessel become laden with calcium, collagen, elastin and
glycosaminoglycans which results in a progressive decrease in elasticity and
compliance thereby impeding the flow of blood supply to vital body tissues and
cells (Steven and James, 1988).
|| Correlation matrix of nutrient intake and blood pressure
|*Correlation significant at the 0.05 level (2-tailed); 1Systolic
Blood Pressure; 2Diastolic Blood Pressure; The Correlation matrix
analysis shown above indicated that, only potassium intake correlated significantly
with both systolic and diastolic blood pressure
|| Odds ratios with 95% confidence interval for potential predictors
of high blood pressure
|The regression coefficient for the entire model; R2
= 0.224, 1: Adjusted for age (years); years of work, income levels,
marital status, educational status, staff categories, waist-hip ratio, body
mass index, percentage body fat, diabetes status, hypertension status, special
diet intake and property owning (car) were included in the regression model,
2: Adjusted for waist-hip ratio; years of work, income levels,
marital status, educational status, staff categories, body mass index, percentage
body fat, diabetes status, hypertension status, special diet intake and
property owning (car) were included in the regression model, 3:
adjusted for body mass index; years of work, income levels, marital status,
educational status, staff categories, percentage body fat, diabetes status,
hypertension status, special diet intake and property owning (car) were
included in the regression model
The prevalence of obesity and overweight cases combined was very high (62.1%) with Body Mass Index, Waist-Hip Ratio and percentage body fat found to be factors that predispose the respondents to high blood pressure. The risk of developing hypertension increased with age with persons within the ages categories 30-39 years, 40-49 years and 50-59 years having odds ratio of 2.55 (95% CI: 1.12 -5.81), 3.34 (95% CI: 1.45-7.68) and 7.56 (95% CI: 2.91-19.84), respectively. Potassium intake correlated significantly and positively with both systolic (r = 0.115, p= 0.04) and diastolic blood pressures (r = 0.133, p =0.02).
The Author sincere gratitude goes to Dr. W. B. Owusu for his concern and sacrificing much of his time in the supervision of this project. Furthermore, I wish to express my thanks to the underground miners in AngloGold mines Obuasi for their dedication to this project. I also extend my thanks to Municipal Health Directorate of the Ghana Health Service.
Determination of sample size: The sample size calculation was done using:
where, n is the sample size, Z is the 95% confidence interval (CI), P is the prevalence of hypertension in the Ashanti Region and d is the percent
Title of study: The Relationship between Dietary Intake, Body Composition
and Blood Pressure in Male Adult Miners in Ghana.
As part of the activities in Nutrition and Food Science Department this year, we have decided to conduct a study on the relationship between Dietary Intake, Body Composition and blood pressure among underground male miners in the Obuasi Municipality.
The purpose is to generate information on these because of the unique nature
of miners. The study will involve participants providing information about their
socio-economic background and the kind of activities they engage in. Another
component will involve you being measured (Weight, Height, Waist circumference,
Hip circumference, Skin fold measurements and Blood pressure). All these procedures
are non-invasive and have no identified risk to your health. We are by this
letter informing you and seeking your consent to be part of the study.
Questionnaire for the study of the Relationship between Dietary Intake, Body Composition and Blood Pressure in Male Adult Miners in Ghana
ASSESSMENT OF BODY COMPOSITION
|F. Skin Fold Thickness Measurements (SFTM)
G. Waist and Hip Circumference Measurements
|BLOOD PRESSURE DETERMINATION
ASSESSMENT OF EATING HABITS/DIETARY PATTERN
a. Food Frequency Questionnaire
|Tell me how many times you have eaten any of these foods within
the past one week
|24-Hour Dietary Recall