Socioeconomic Features of People with Hypertension Screened for Diabetes
A. N. Adamu*, A. E. Ohwovoriole†, J. K. Olarinoye*, O. A. Fasanmade†,
C. O. Ekpebegh†, G. M. Oyeyemi‡.
*Endocrinology and Metabolism Unit, Department of Medicine, University of Ilorin, Nigeria.
† Endocrinology and Metabolism Unit, Department of Medicine, University of Lagos, Nigeria.
‡Department of Statistics, University of Ilorin, Nigeria.
Address correspondence and reprint to Abdullahi N. Adamu, Department of Medicine, University of
Ilorin, Ilorin, Kwara State, Nigeria.
ABSTRACT
Background- The association of many vascular diseases and their risk factors with socioeconomic status has been
well described in western worlds. Certain risk factors implicated in the development of diabetes are also known to
be associated with socioeconomic status. However, no study has been carried out among our cohort to assess the
association between socioeconomic status and diabetes.
Aim- To determine the effect of SEC factors on the prevalence of diabetes among people living with systemic
hypertension.
Methods- We recruited 206 persons for administration of socioeconomic status questionnaire; 129 (62.6%) were
females and 77 (37.4) were males. 126 (participation rate of 61.16%) of them had OGTT; 84 were females
constituting 66.7% while males were 42 in number constituting 33.3%.
The socioeconomic stratification was done by categorization of educational attainment, annual income and
occupation. A scoring system was assigned to the categories as following: Educational category is; none=1, Basic
Arabic and Islamic education/Primary/ modern school=2, Secondary =3, Advanced Teacher Training/Polytechnic =
4 and University=5. Occupational social status is; Unemployed= 1, Petty Trading/Artisans=2 (includes driving,
tailoring, small scale farming, hairdressing, plumbing, bricklaying etc. ), Clerk/Typist= 3, Teaching/Middle Level civil
servants= 4, Professionals= 5 ( includes top civil servants and businessmen ). Income per year category is based on
minimal wage in Nigeria (11) in naira currency as follows; Nil income or < 67009 =1, 67010 – 71372 = 2, 71373 –
134079 = 3, 134080 – 242068 = 4, 242070 – 340332 = 5, >340332 = 6. The summation of the categorical scores
(Socioeconomic Class (sec) score Grading) were also assessed as follows; Lower SEC <9, Lower middle SEC = 9 – 11,
Upper middle SEC =12 – 14, Upper SEC >15. 2hr Oral glucose tolerance result of ≥200mg/dl was considered to be
diabetes.
We used SPSS version 11 to analyze the data. The analysis begins with an examination of the descriptive statistics.
Differences among groups were assessed using chi square and P Value of ≤0.05 was considered to be significant.
The primary focus of the analyses are presented as odds ratios (ORs) which helped to detect the bivariate
relationships between social factors and the risk of type 2 diabetes. The baseline odds are set at 1.0. An OR ≥ 1.0
indicates that there is a positive association between the social factors to diabetes odds while a value <1.0
indicates the inverse. For statistically significant relationships, 95% confidence intervals (95% CI) were also
calculated.
Results- - The overall mean age of the 206 participants was 54.38±9.35. The mean age of the females is 54.29±8.66
while that of the males is 54.53±10.47. The descriptive statistic shows a significant difference between those that
have diabetes and those who do not have diabetes. The odds ratio of having diabetes was significant in low
earning and high education profile. We also found out that earning is more significant a measure of SEC in our
cohort.
1
Keywords- Earning, Education, Occupation, Socioeconomic factor (sec) and diabetes.
Introduction.
Socioeconomic inequalities in morbidity and mortality have been widely documented (1-3). Throughout the world,
social scientists continue to pay close attention to the relationship between social inequalities and health (4). One
of the greatest achievements of our modern health-focused society has been the dramatic increase in life
expectancy. However, life expectancy is significantly lower among persons with lower levels of education, income,
and occupational prestige since socioeconomic status (SES) inequalities have profound effects on health status (5).
The three most commonly employed indicators of socioeconomic status in contemporary industrialized societies
are income, education, and occupation (6).
Type 2 diabetes is more prevalent in lower socioeconomic groups in Western societies (7). Diabetes is a significant
public health problem with its associated cardiovascular morbidity and mortality, and there are predictions that it
may reach epidemic proportions by the year 2025 (8). Most of the African countries are in abject poverty and
penury (9). The poverty index of Nigeria is 54.4% and the population below poverty line of one US Dollar per day is
about 54.5% (9). Nigeria is ranked as the 158th out of 177 poor countries in the world (9). No study is available to
adjudge the impact of this malady among people living with diabetes.
We investigated the independent contribution of educational level, occupational social class, income and sum of
these variables to development of Type 2 diabetes in a sample of people with systemic hypertension attending a
tertiary institution in Lagos, Nigeria.
METHODS
Study Design: Cross sectional studies
Study Location: This study was carried out at the Lagos University Teaching Hospital (LUTH), over a period of three
months, spanning from January to March 2004. The Lagos University Teaching Hospital is located in Idi-Araba on
the mainland and functions as a tertiary health care centre. Lagos is the former capital of Nigeria and serves as the
commercial nerve centre of the country.
Subjects: The subjects were People with known history of systemic hypertension on life-style modification and/ or
drug (s) for the control of the hypertension in Medical out Patients’ Department of the hospital. They were
recruited for the screening exercise for type 2 diabetes. Those patients with established secondary form of
hypertension, chronic renal failure and chronic liver disease were excluded from the study.
Sample Size:
We recruited 206 persons for administration of socioeconomic status questionnaire. One hundred and twenty
nine (62.6%) were females and seventy-seven (37.4%) were males. One hundred and twenty- six (participation rate
of 61.16%) of them had OGTT; 84 were females constituting 66.7% while males were 42 in number constituting
33.3%.
Approval was obtained from the Ethical Committee of the Lagos University Teaching Hospital. An informed consent
was obtained from the patients/ subjects before commencing the studies.
The patients on usual medical follow up were approached and given a brief health talk on the importance of
screening for diabetes among people with systemic hypertension. A questionnaire containing biodata and
socioeconomic information of the subjects were taken. The information taken include: name, age, gender, hospital
number, level of education earning per annum and type of occupation. The socioeconomic stratification was done
by categorization of educational attainment, income and occupation and by assigning scoring system to the
2
categories. Educational category was scored as follows; none=1, Basic Arabic and Islamic education/Primary/
modern school=2, Secondary =3, Advanced Teacher Training/Polytechnic = 4 and University=5. Occupation social
status was scored as follows; Unemployed= 1, Petty Trading/Artisans=2 (includes driving, tailoring, small scale
farming, hairdressing, plumbing, bricklaying etc. ), Clerk/Typist= 3, Teaching/Middle Level civil servants= 4,
Professionals= 5 ( includes top civil servants and businessmen ). Income per year category was based on minimal
wage in Nigeria (11) in naira currency as follows; Nil income or < 67009 =1, 67010 – 71372 = 2, 71373 – 134079 = 3,
134080 – 242068 = 4, 242070 – 340332 = 5, >340332 = 6. The summation of the categorical scores (Socioeconomic
Class (sec) score Grading) were also assessed as follows; Lower SEC <9, Lower middle SEC = 9 – 11, Upper middle
SEC =12 – 14, Upper SEC >15. There is no gender sensitivity in the scoring system, as each of the gender is assessed
independently.
The form also had provision for 2hours venous plasma glucose after a standard 75gram of dissolved anhydrous
glucose intake. Those who had questionnaire applied were given another day, a week to come to the endocrine
laboratory of Department of Medicine to come for oral glucose tolerance test (OGTT). They all arrived before 7.30
am for OGTT and in a fasting state after the previous day dinner.
At 7.30am, all had their fasting venous blood taken and were given 75gm of dissolved anhydrous glucose in chilled
water to drink at once and another sample was taken at 9.30am. Immediately, after the venous blood was drawn,
all were centrifuged, and aliquots were prepared within 30min of collection. Plasma aliquots were frozen at -80oC
until analysis in the same laboratory. Plasma glucose was analyzed according to the method of Trinder (12) using
glucose oxidase enzyme buffered in phenoxylate and dissolved in colour reagent. The coefficient of variation for
intra-assay was 3.5% and inter-assay was 9%. Two hours post glucose venous plasma of ≥11.1mmol-1 defined
diabetes using OGTT as gold standard.
Statistical Analysis
At the end of the exercise all the data were entered into a Microsoft Excel database. We used SPSS version 11 to
analyze the data. The analysis began with an examination of the descriptive statistics (frequencies) for both the
dependent and independent variables. Differences among groups were assessed using chi square.
The analyses were taken for mean 2hours plasma glucose. The primary focus of the analyses were presented as
odds ratios (ORs) which helped to detect the bivariate relationships between social factors and the risk of type 2
diabetes. The baseline odds were set at 1.0. An OR ≥ 1.0 implies positive association between the social factors to
diabetes odds while a value <1.0 indicates the inverse. For statistically significant relationships, 95% confidence
intervals (95% CI) were also calculated.
The proportions in each category were tabulated according to the three measures of socioeconomic status: social
class of education, earning, occupation and the sum of the categories; socioeconomic class.
Results- The overall mean age of the 206 participants was 54.38±9.35. The mean age of the females is 54.29±8.66
while that of the males is 54.53±10.47. Table 1 shows the baseline characteristic features of the participants based
on gender and the socioeconomic indicators (level of education, job description, earning and socioeconomic class).
Assessment of level of significance across the gender shows that level of education in second category, job
description in 5th category and first category in earning and socioeconomic class were significant. No data was
available for 2nd category in earning. The level of significance within the gender shows level of significance to exist
in education and earning within female category and job description, socioeconomic class in both genders.
Table 1 Baseline characteristics of study population base on gender and socioeconomic indicators.
M 77
F 129
P value
Number/percent Number/percent
Level of Education
1
4/5.2
14/10.9
>0.05
2
19/24.7
42/32.6
<0.05
3
3
4
5
P value
Job Description
1
2
3
4
5
P value
Earning Category
1
2
3
4
5
6
P value
Socioeconomic Class
1
2
3
4
P value
1924.7
19/24.7
16/20.8
>0.05
31/24.0
27/20.9
15/11.6
<0.05
>0.05
>0.05
>0.05
1/1.3
43/55.8
18/23.4
6/7.8
9/11.7
<0.05
18/14
65/50.4
34/26.4
12/9.3
0/0
<0.05
<0.05
>0.05
>0.05
>0.05
<0.05
16/20.8
0
8/10.4
19/24.7
13/16.9
21/27.3
>0.05
67/52.3
0
14/10.9
16/12.5
8/6.3
24/18
<0.05
<0.05
24/31.2
33/42.9
12/15.6
8/10.4
<0.05
83/64.8
16/12.5
18/14.1
11/8.6
<0.05
<0.05
>0.05
>0.05
>0.05
>0.05
>0.05
>0.05
>0.05
Of the 126 subjects who had oral glucose tolerance done, 105 had 2hour glucose result of < 200mg/dl,
consisting of 69(65.7%) females and 36(34.3%) males. Twenty-one had 2hour glucose result of ≥200mg/dl;
15(71.4%) females and 6(28.6%) males. The mean age of patients with 2hour glucose less than 200mg/dl category
is 52.87±9.02, while those with ≥200mg/dl is 53.76±7.80. The mean age value is not statistically significant.
Assessment of level of significance within mean 2hour blood glucose estimation across the socioeconomic strata
shows P value ≤0.05 under job description in both plasma glucose category, and earning and socioeconomic class
in those with plasma glucose <200mg/dl. Also the assessment of level of significance across the two plasma
glucose measurement and measure of socioeconomic stratifications shows P value of <0.05 except in the first
category of level of education and the third category of socioeconomic class.
Table 2 Mean 2 hour plasma glucose by social class categorization.
<200mg/dl
≥200mg/dl
P value
Number/percent Number/percent
Job description
1
13(12.4)
1(4.8)
<0.05
2
52(49.5)
14(66.7)
<0.05
3
24(22.9)
5(23.8)
<0.05
4
10(9.5)
1(4.8)
<0.05
5
6(5.7)
0
<0.05
P value
<0.05
<0.05
4
Level of education
1
2
3
4
5
P value
Earning
1
2
3
4
5
6
P value
Socioeconomic class
1
2
3
4
P value
9(8.6)
29(27.6)
24(22.9)
22(21.0)
21(20.0)
>0.05
2(9.5)
7(33.3)
4(19.0)
7(33.3)
1(4.8)
>0.05
>0.05
<0.05
<0.05
<0.05
<0.05
<0.05
39(8.6)
10(47.6)
<0.05
14(13.3)
14(13.3)
13(12.4)
25(23.8)
<0.05
1(4.8)
3(14.3)
2(9.5)
5(23.8)
>0.05
<0.05
<0.05
<0.05
<0.05
52(49.5)
24(22.9)
16(15.2)
13(12.4)
<0.05
12(57.1)
3(14.3)
6(28.6)
0(0)
>0.05
<0.05
<0.05
>0.05
<0.05
Figures 1-5 show graphically the odd ratios of uncategorized and categorized socioeconomic status of the subjects
and 95% confidence intervals. The uncategorized class in fig 1 shows significant association with the risk of
developing Type 2 diabetes in earning and SEC class. This is also the same in educational level 4 in figure 3 and
earning category 1 in figure 4.
3.5
3
2.5
2
High
Low
1.5
Close
1
0.5
0
Job descrip Education
Earning
SEC
Figure 1 Odds ratio (95% confidence intervals) of uncategorized socioeconomic class of the subjects.
5
9.00E+30
8.00E+30
7.00E+30
6.00E+30
5.00E+30
High
Low
4.00E+30
Close
3.00E+30
2.00E+30
1.00E+30
0.00E+00
Job description 1
Job description 2
Job description 3
Job description 4
Figure 2 Odds ratio for job categorization
140
120
100
80
High
Low
60
Close
40
20
0
Level of education1 level of education2 Level of education3 Level of education4
Figure 3 Odds ratio for educational level categorization.
6
80
70
60
50
High
40
Low
Close
30
20
10
0
Earning cat1
Earning cat2
Earning cat3
Earning cat4
Figure 4 0dds ratio of income earned by the subjects in categorized form.
1.00E+25
9.00E+24
8.00E+24
7.00E+24
6.00E+24
High
5.00E+24
Low
4.00E+24
Close
3.00E+24
2.00E+24
1.00E+24
0.00E+00
SEC 1
SEC 2
SEC 3
Figure 5 0dds ratio of categorized socioeconomic class.
7
Discussions - The descriptive statistic analysis of socioeconomic factors to the result of OGTT stratification showed
a significant difference, the odds ratio of the socioeconomic factors to risk of having diabetes was significant for
earning, particularly for category 1, for uncategorized SEC and for educational level 4. Since odds ratio is more
important a measure of diabetes risk, one could assert that there is ambivalent association between the social
status and diabetes in our setting. This tilt the balance between educationist and unlearned people, one will
presume that the level of education should go along with earning, however because of high level of
unemployment, a situation where you have lot of university graduates or learned individuals not gainfully
employed shall presumptively put them in poor category. Whereas, those who are low profile educationist will not
mind doing blue-collar job to earn a living, which will possibly put them at a better economic advantage compare
to the high profile educationist, thus, income quartile seems attractive as it produced the most consistent
gradients (13). Consequently, those who do blue collar job burnt off any energy that is stored in them as a result of
food consumption and they also consume high fiber diet that is the common food constituent in our environment,
while high profile educationist who relatively engaged in physical demanding job and may likely go for calorie
dense meals contributing to their body mass index (BMI) which is one of the major risk factor for diabetes in our
setting.
The findings in this study is similar to what obtains in western world where low SEC was generally associated with
poor cardiovascular profile of which type 2 diabetes is one the main arbinger (14). In US and UK, excess mortality
risk for lower income groups was explained by 4 health behaviours: smoking, alcohol drinking, lack of physical
activities and high BMI (15 &16). These factors are also common among our elite, though study has not being
carried out to ascertain the level of significance. Also, in Newcastle upon Tyne, the prevalence of diabetes
increased with lower social class, and other less consistent indentified markers for diabetes were smoking and
dietary constituents such as fat constituents and antioxidant vitamins (17)
Conclusion
This study has found earning to be more important as a measure of SEC in our cohort and described a significant
inverse association between type 2 diabetes and SEC.
Limitations
Limited number of subjects were used, different SEC indices were used in this study compare to other studies.
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