European Heart Journal (1997) 18, 588-595
Social class and coronary disease in a rural
population of north India
The Indian Social Class and Heart Survey
R. B. Singh, J. P. Sharma, V. Rastogi, M. A. Niaz, S. Ghosh, R. Beegom and
E. D. Janus
Centre of Nutrition and Heart Research Laboratory, Medical Hospital and Research Centre, Moradabad, India;
Clinical Biochemistry Unit, Queen Mary Hospital, Hong Kong
Objective To demonstrate the association of socioeconomic status with prevalence of coronary artery disease
and coronary risk factors.
Design and setting Cross-sectional survey in two randomly selected villages in the Moradabad district in North
India.
Subjects and methods One thousand seven hundred and
sixty-seven subjects (894 males and 875 females; 25-64
years of age) were randomly selected from two villages.
They were divided into social classes 1 to 4, according to
education, occupation, housing conditions, ownership of
land, ownership of consumer durables and per capita
income. The survey was based on questionnaires administered by dietitians and physicians, physical examination
and electrocardiography.
significant association with higher serum cholesterol, body
mass index, triglycerides and blood pressures. Logistic
regression analysis with adjustment for age showed that
social class positively related to coronary disease (odds
ratio: men 083, women 0-61), hypercholesterolaemia (men
0 85, women 0-87), hypertension (men 0-89, women 0-87),
body mass index (men 0-91, women 0-93) and smoking in
men (0-68). Smoking and sedentary lifestyle were not associated with social class in women. The association between coronary artery disease and social class abated after
adjustment for smoking, sedentary lifestyle, body mass
index and blood pressure (odds ratio: men 0-96, women
0-81).
Conclusion Subjects in social classes 1 and 2 in rural
North India have a higher prevalence of coronary artery
disease and of the coronary risk factors hypercholesterolaemia, hypertension, higher body mass index and sedentary
Results Social classes 1 and 2 were mainly high and middle lifestyle. The overall prevalence of coronary artery disease
socio-economic groups and 3 and 4 low income groups. The was 3-3%.
prevalence of coronary artery disease was significantly (Eur Heart J 1997; 18: 588-595)
higher among classes 1 and 2 in both sexes, and there was a
higher prevalence of hypercholesterolaemia, hypertension, Key Words: Serum cholesterol, lifestyle, dietary fat, risk
and sedentary lifestyle. This population also showed a factors.
prevalence are higher among wealthy communities16"11!.
However, a recent study1121 from a rural area showed
that
among uneducated and less well educated people
In most developed countries, coronary risk factors,
which are an important determinant of coronary artery coronary disease tendency is high. In this study'12',
disease, are highly prevalent in lower social classes1'"51. important attributes of social class, diet, economic
However, large scale studies from developing countries status, consumer durables and occupation were not
show no such correlation. Indian studies indicate that considered. Social class, prevalence of coronary risk
coronary risk factors and coronary artery disease factors and coronary artery disease have also not been
studied adequately in other developing countries'13'141.
More than half the population of rural North
Revision submitted 18 October 1996, and accepted 23 October
India are illiterate and one third are undernour1996.
ished'15161. In India, dietary intake is related to socioCorrespondence: Dr R. B. Singh, Hon. Professor of Preventive
available fat
Cardiology, Heart Research Laboratory, MHRC, Civil Lines, economic status. Forty-five percent of the 151
is consumed by the higher income groups' . National
Moradabad-10 (UP) 244001. India.
Introduction
0195-668X/97/O4O588 + 08 SI8.00/0
1997 The European Society of Cardiology
Social class and coronary artery disease
surveys and other studies indicate that per capita income, better housing, ownership of land, occupational
status and education were positively associated with
higher intake of dietary fat" 5 -' 9 '.
The Indian Social Class and Heart study examines, possibly for the first time in adequate detail,
whether social class based on these attributes is associated with coronary artery disease and coronary risk
factors. The Seven Countries Study'20' has shown that
the risk from major risk factors is universal. However,
the strength of the risk factors varies from community to
community, and as is evident from our study, is due to
other factors.
Subjects and methods
Details of subjects and methods used in this study have
been described in the pilot survey'19'. In brief, 68 villages
in the Moradabad Tahsil have a population of 1000—
5000 subjects, making the total population in the Tahsil
01 million (Census, 1991)[21]. We randomly selected
two villages and from each two to three blocks from
each street. Each block contained 100-300 adults. We
selected 2000 subjects for this study. When the random
number fell on a subject more than 64 years or less than
25 years of age, the next subject in the list was chosen.
The total study sample was 1974 subjects between 25
and 64 years of age. Two hundred and five (9-5%)
subjects refused to give a detailed history or blood for
examination. Social class, age and sex in this subgroup
were comparable with the study sample. All subjects
included in the study had lived in the area since birth. Of
the remaining 1769 adults, 894 males and 875 females
were invited to participate in the study. The sex ratio for
these age groups were comparable with available census
data'22'.
A questionnaire administered by physicians and
dieticians was prepared based on the guidelines of the
World Health Organization'221 and Indian Council of
Medical Research and other Indian studies'15"17'. The
questionnaire was validated'19' and included detailed
information on age, sex, education, socio-economic
status, physical activity, past and family history of
hypertension, diabetes, chest pain (Rose Questionnaire'22'), smoking and alcohol consumption. A socioeconomic status measurement scale was constructed,
based on earlier studies from India. Social class was
graded 1-4 based on the classification of Raman Kutty
and coworkers'"'. The scores were assigned to each
subject based on education, occupation, housing conditions, ownership of consumer durables, ownership of
land and per capita total income of the family members.
Per capita income was calculated by total family income
from all sources divided by the total number of family
members. Educational status was assessed from the
number of years in education. Housing conditions and
consumer durables were assessed as described in the
earlier studies'"'17'. Social class 1 was considered the
highest and 4 the lowest socio-economic status.
589
Dietary intake was assessed from subjects 7-day
food intake record diaries. These were filled in for a
year. Food measures, food models and food portions
were measured, according to World Health Organization guidelines'22'. Nutrient intake was calculated using
Indian food composition tables'23' based on the food
intake record. Physical examination included measurements of height, weight and blood pressure. Body
weights were measured by the dietitian independently in
light underclothes to the nearest of 0-5 kg. Height was
measured in the standing position. Blood pressure
(systolic and diastolic phase V of Korotkoff) was
measured in the right arm after 5 min rest in the sitting
position. The same physician measured all subjects with
a standard mercury manometer. When high blood
pressure (> 140/90 mmHg) was noted, a final reading
was recorded in the lying position after 5 min rest, as per
World Health Organization guidelines'22'. A 12-lead
electrocardiogram was recorded in all subjects.
Diagnostic criteria
Hypertension was diagnosed when the systolic blood
pressure was 140 mmHg or more and the diastolic
90 mmHg or more as per the guidelines of the United
States national health and nutrition assessment survey'24'. The older WHO criteria (> 160/95 mmHg) were
also recorded. Body mass index was calculated and
obesity defined as a body mass index of >27 kg . m~ 2
and overweight as a body mass index > 2 5 k g . m ~ 2 .
Figures for criteria laid down by the Indian Consensus
Group for Overweight (>23 kg. m ~ 2 ) were also calculated. Hypercholesterolaemia was diagnosed if
serum cholesterol was more than 5-18 mmol. 1~'
(>200 mg . dl~ ') and hypertriglyceridaemia if serum
triglycerides
were
more
than
2-08 mmol. 1
(>185 mg . dl~ ] ). Diabetes mellitus was diagnosed if the
fasting blood glucose was more than 7-7 mmol. ~'
(>140mg.dl )
more
than
111 mmol . 1"
(>200 mg . dl l) 2 h after 75 g oral glucose. Postprandial blood glucose between 7-7 and 11-1 mmol. 1~'
(140-200 mg . dl~') was considered glucose intolerance.
In India, cigarettes, beedies, Indian pipes, raw
tobacco and chewing tobacco are commonly consumed
and people use tobacco in more than one form. We
therefore categorized users of any form of tobacco as
smokers, as was done in other studies'12'. Subjects
who admitted to drinking alcohol more than once a
week were categorized as alcohol consuming. Physical
activity was assessed by ascertaining both occupational
and recreational activities. According to Paffenberger
et a/.'25', a person leads a sedentary lifestyle if they walk
less than 14-5 km a week, climb fewer than 20 nights
of stairs a week or perform no moderately vigorous
physical activity on any 5 days a week.
Coronary artery disease was diagnosed'22' if one
or more criteria were satisfied: (a) documented history
of chest pain suggestive of angina or infarction and
previously diagnosed as coronary artery disease;
Eur Heart J, Vol. 18, April 1997
590
R. B. Singh et al.
Table 1 Distribution (n (%)) of social classes 1-4 among different age groups
Age groups
(years)
No. of
subjects
Social
class 1
Social
class 2
Social
class 3
Social
class 4
Males (n = 894)
25-34
35^4
45-54
55-64
Total
300
296
178
120
894
60
52
23
12
147
(20 0)
(17-5)
(12-9)
(100)
(16-4)
65
50
22
10
147
(21 6)
(16-8)
(13-4)
(8-3)
(16-4)
80
104
65
38
287
(26-6)
(351)
(36-5)
(31-6)
(32-1)
95
90
68
60
313
(31-6)
(30-4)
(38-2)
(50-0)
(350)
Females (n = 875)
25-34
35^4
45-54
55-64
Total
350
264
165
96
875
50
40
14
11
115
(14 2)
(15-1)
(8-4)
(11-4)
(131)
54
36
16
6
112
(15-4)
(13-6)
(9-7)
(6-2)
(12-8)
110
98
65
40
313
(31-4)
(37-1)
(39-4)
(41 4)
(35-7)
136
90
70
39
335
(38-8)
(340)
(42-4)
(40-6)
(38-3)
(b) affirmative response to the Rose questionnaire after
excluding any obvious cause of pain due to local factors;
(c) coronary artery disease was also diagnosed in the
absence of (a) and (b) but in the presence of electrocardiographic changes, namely Minnesota code 1-1-1 to
1-1-7 or 1-2-1 to 1-2-7; the presence of a major ST
segment and major T wave and Q wave changes, or Q
wave changes in the absence of a high voltage R wave.
Minnesota codes 4-1-1 and 4-1-2 and 5-1 and 5-2 were
also diagnosed as coronary artery disease.
In all subjects, a blood sample was collected in
the sitting position using a tourniquet after an overnight
fast. An enzymatic method was used to estimate total
cholesterol and triglycerides. High density lipoprotein
cholesterol was estimated after precipitation of nonhigh density lipoprotein cholesterol with manganese
heparin substrate. Low density lipoprotein cholesterol
was obtained using Frediewald's formula: low
density lipoprotein = total cholesterol — high density
lipoprotein - (triglyceride/5). Each participant was
asked to drink 75 g anhydrous glucose in 200 ml of
water and a second blood sample was collected after 2 h
for analysis of glucose. All blood samples were analysed
on the day of blood collection.
Statistical analysis
It is assumed, from other studies, that the prevalence of
coronary disease is about 5% in the community. We thus
needed a sample of at least 1500 subjects to estimate,
with 90% confidence and 5% significance, a relative risk
of 1-54 for the prevalence of coronary disease in Indians.
We wanted a larger sample size to increase the level of
confidence and to estimate the prevalence to within a 2%
error on either side. This was deemed satisfactory as a
first estimate.
Multivariate analysis to determine the overall
relationship of social class with coronary artery disease
and risk factors was performed by logistic regression.
The dependent variables were presence or absence of
Eur Heart J, Vol. 18. April 1997
coronary disease, hypertension, smoking, physical activity, obesity and hypercholesterolaemia. Independent
variables were social class, age and physical measurements. Initially, a relationship between social class and
risk factor was determined. Age, which is the major
confounding factor, was then added to the equation and
odds ratios determined and tabulated. Odds ratios were
finally calculated for coronary artery disease, after adding absolute values of body mass index, blood pressure,
serum cholesterol, smoking and sedentary lifestyle to the
equation. All P values were two tailed and significance
was taken as P<005.
Results
The social classes of the different age groups of the 894
males and 875 females are shown in Table 1. There
was an inverse correlation of age with social class (Spearman's r=men - 0-42, women - 0-46, /><0001). The total prevalence of coronary artery disease between 25-64
years of age was 3-27% (n = 58) with a prevalence of 3-9%
(n = 35) in males and 2-6% (n = 23) in females. An overall
increase in the prevalence of coronary artery disease in
higher social classes 1 and 2 was apparent in both sexes
and the trend was significant in both men and women
(Table 2). With respect to electrocardiographic changes
ST-T and Q wave changes were significantly higher
among social classes 1 and 2 compared to class 3. Q wave
changes were significantly higher in class 1 compared to
class 2 in men but, due to fewer cases, not in women.
Sedentary lifestyle was more common in females than males but moderate physical activity was
comparable in both sexes. Smoking was common
among males but rare in females. A quarter of subjects
were overweight and hypertension (>140mmHg) was
common in both sexes. Dyslipidaemias are observed in
about 10% of the subjects in both sexes (Table 3).
Dietary fat intake was low in both sexes (Table 3).
However, social classes 1 (26-5 ± 4 1 % k c a l . day" 1 )
and 2 (23-2 ±4-0% kcal. d a y " ' ) consumed signifi-
Social class and coronary artery disease
591
Table 2 Social class and prevalence of coronary artery disease. (n (%))
Females (n = 875)
Males (n = 894)
Socio-economic
status
Social
Social
Social
Social
Total
class
class
class
class
Clinical and
electrocardiographic
1
2
3
4
17
15
2
1
35
Mentel-Haenzel Chi-squared
P value
(115)
(10-2)
(0-7)
(0-3)
(3-9)
12-6
<0001
ST-T and
Q wave
changes
14
13
2
1
30
Q wave
only
11
4
1
1
17
(9-5)
(8-8)
(0-7)
(0-3)
(3-3)
15-8
<001
Clinical and
electrocardiographic
ST-T and
Q wave
changes
Q wave
only
12 (104)
10 (8-7)
6 (5-3)
2 (0-6)
—
18 (20)
4 (3-5)
2 (1-8)
—
—
6 (0-7)
8-6
<001
4-2
<006
(7-4)
(2-7)
(0-3)
(0-3)
(1-9)
9 (80)
2 (0-6)
—
23 (2-6)
9-5
<0001
8-5
<002
Table 3 Prevalence of coronary risk factors in males and females (n (%))
Sedentary lifestyle
Moderate physical activity
Smoking
Smoker (> 15. day" 1 )
Moderate smoker (1-15 . day" ')
Total
Alcohol intake
Body mass index (kg . m ~ 2)
>27
>25
>23
Diabetes mellitus
Glucose intolerance
Hypertension (mmHg)
Blood pressure (> 140/90)
Blood pressure (> 160/95)
Abnormal lipid levels
Cholesterol (>518mmol. 1"')
Low density lipoprotein
cholesterol (>3-21 mmol. 1 ~ ')
High density lipoprotein
cholesterol (<0-9 mmol. 1 ~ ')
Triglycerides (>2-08 mmol . 1" ')
Dietary fat intake (% kcal. d a y " ')
Males
(n = 894)
Females
(n = 875)
Total
(n=1769)
126 (140)
450 (50-3)
228 (26-0)
462 (52 8)
354 (200)
912 (51-5)
210 (23-4)
90 (100)
300 (33-4)
27 (3-0)
5 (0-6)
46 (5-2)
51 (5-8)
—
45
96
212
27
37
(50)
(10-7)
(23-7)
(3-0)
(4-1)
46
100
220
24
34
(5-2)
(11-4)
(25 1)
(2-7)
(3-8)
215
136
351
27
(121)
(7 6)
(19-8)
(1-5)
91
196
432
51
71
(5-1)
(110)
(24-4)
(2-8)
(40)
156 (17-4)
45 (50)
151 (17-2)
36 (41)
307 (17-3)
81 (4-5)
92 (10-2)
84 (9 3)
87 (9-9)
82 (9-3)
179 (10-1)
166 (9-4)
72 (80)
54 (6-2)
126 (71)
88 (9-8)
15-6 (3)
85 (9-7)
15-2 (3)
173 (9-8)
15-4 (4)
cantly more dietary fat than social classes 3 (13-5 ±
3-2% kcal. day ~ ') and 4 (90 ± 2-2% kcal. day" '). As
the social class level rose so did the trend in the
prevalence of hypercholesterolaemia, hypertension, diabetes mellitus and sedentary lifestyle, in both men and
women. There was no significant association of smoking with social class. Mean body mass index, total
cholesterol and systolic and diastolic blood pressure
showed a significant falling trend as social classes
lowered in both men and women (Table 4). No such
significant trend was observed with low and high
density lipoprotein cholesterol. There was a significant
lowering trend in triglyceride concentrations with decreasing social class in both sexes (Table 5). There was
also a significant positive rank correlation of the level
of socio-economic status with weight, body mass index,
systolic and diastolic blood pressure, total cholesterol
and dietary fat intake in both sexes. Age also showed a
significant inverse rank correlation with level of social
class in both sexes (Table 6).
Multivariate logistic regression analysis was performed to determine the relationship of social class with
coronary artery disease and the prevalence of coronary
risk factors (Table 7). The results showed a significant
positive association between levels of social class and
age-adjusted prevalence of coronary artery disease,
higher blood pressure, serum cholesterol, body mass
index and sedentary lifestyle. Smoking in males was also
associated with coronary disease. No association was
observed with smoking and sedentary lifestyle in
females. Adding smoking, sedentary lifestyle, body mass
index, systolic and diastolic blood pressure and serum
Eur Heart J. Vol. 18, April 1997
592 R. B. Singh et al.
Table 4 Prevalence of coronary risk factors in relation to socio-economic status
Socio-economic
status
Males
Social
Social
Social
Social
class
class
class
class
No. of
subjects
1
2
3
4
Cholesterol
>5- 18 mmol. 1
147
147
287
313
47
38
46
25
48 (32 6)
40 (27-2)
4 (1-4)
—
Mentel-Haentzel Chi-squared
P value
Females
Social class
Social class
Social class
Social class
Blood pressure
>140.90mmHg
1
6-65
<001
1
2
3
4
115
112
313
335
716
<007
57
28
60
26
45 (39-1)
38 (33-9)
4 (1-3)
Mentel-Haentzel Chi-squared
P value
(32 9)
(25-8)
(160)
(8-0)
(32-2)
(25-0)
(19-2)
(7-7)
10-62
<0001
8-84
<0001
Smoking
50
55
90
105
(340)
(37-4)
(31-3)
(33-5)
3-55
<005
7
8
16
20
(60)
(71)
(5-1)
(5-9)
0-26
035
Diabetes
mellitus
9
8
7
3
(61)
(5-4)
(2-4)
(0-9)
5 21
<005
8
6
7
3
(6-9)
(5-3)
(2-2)
(0-9)
5-26
<005
Sedentary
lifestyle
65 (44-2)
51 (34-6)
10 (3-5)
—
5-82
<002
84
65
64
15
(130)
(58-0)
(20-4)
(4-4)
6-88
<001
Table 5 Risk factor levels in relation to socio-economic status
Socio-economic
status
Males
Social
Social
Social
Social
class
class
class
class
1
2
3
4
Kendall's x (tau)
t value
Social
Social
Social
Social
class
class
class
class
1
2
3
4
Kendall's x (tau)
t value
Body mass
index (kg . m~ 2 )
23-2
22-6
21-5
19-6
Total
cholesterol
(mmol. I" 1 )
(4)
(3)
(4)
(3)
0057
2-57*
231
22-4
21-6
19-5
(3)
(3)
(4)
(4)
0061
2-65*
5 21
501
4-30
3-36
(1-3)
(1-4)
(1-5)
(1-3)
0056
2-53*
5-22
5-02
4-20
3-32
(1-5)
(1-3)
(1-4)
(1-2)
0-52
2-50*
LDLcholesterol
(mmol . 1 " ' )
2-65
2-36
2-25
2-12
(0-6)
(0-5)
(0-7)
(0-6)
(0 5)
(0-7)
(0-6)
(0-5)
0031
1-41
1-20
118
118
115
(0-13)
(012)
(011)
(012)
-0031
- 1-40
0-26
1-22
2-64
2-37
2-22
211
HDLcholesterol
(mmol . 1~')
1-24
1-23
1-22
117
(0-12)
(011)
(0-12)
(0-13)
0028
-115
Triglycerides
1
(mmol.r )
1 58 (0-6)
1 -51 (0-5)
1-45 (0-6)
1 32 (0-5)
0-058
2-41
1-56
1-53
1-44
1-35
(0-5)
(0-5)
(0-6)
(0-6)
0051
2-65*
Blood pressure (mmHg)
Systolic
126
124
120
118
(13)
(12)
(10)
(11)
010
4-52**
125
122
118
115
(14)
(12)
(11)
(10)
0085
415**
Diastolic
84
82
78
72
(11)
(10)
(9)
(8)
0-86
4-12*
88
84
78
70
(12)
(10)
(9)
(8)
0-082
3-81**
Values are mean 1 standard deviation; LDL = low density lipoprotein; HDL = high density lipoprotein.
*/><001, **/><0001.
cholesterol to the equation negated the association of
level of socio-economic status with the prevalence of
coronary artery disease in both males (odds ratio 0-96,
95% confidence interval 0-82 to 118) and females (odds
ratio 0-81, 95% confidence interval 0-50 to 109).
Discussion
The Indian Social Class and Heart Survey showed
that coronary artery disease and coronary risk factors
were significantly associated with social class in a rural
population of North India. Social classes 1 and 2 were
associated with a higher prevalence of coronary artery
disease. This association remained significant on ageadjusted analysis, but declined after the addition of
other lifestyle characteristics in a multivariate analysis.
Higher blood pressure, serum cholesterol, diabetes melEur Heart J. Vol. 18. April 1997
litus and sedentary lifestyle were significantly associated
with social classes 1 and 2. Smoking was not associated
with social class. However, smoking (34% vs 6%) may be
the cause of the higher prevalence of coronary disease in
men compared to women (3-9 vs 2-6%) respectively.
The Indian population is under transition from
poverty to affluence, similar to other developing
countries, in association with rapid changes in diet and
lifestyle'14"19'26"281. The prevalence of coronary artery
disease has almost doubled in the last two decades in
both rural and urban populations of India1261 and
the disease is more common among professionals,
the business class, shop keepers, skilled workers and
rich farmers'6"12'. Contrary to these findings, a recent
American Heart Association scientific statement'281
reiterated that coronary artery disease and coronary risk
factors have become more prevalent among uneducated
Social class and coronary artery disease
593
Table 6 Mean levels of clinical and biochemical risk factors and their correlation
with socio-economic status (figures in parentheses are 1 SD). (Spearman's rank
correlation
Males
Mean age
Mean body weight (kg)
Body mass index (kg . m ~')
Systolic blood pressure (mmHg)
Diastolic blood pressure (mmHg)
Total cholesterol (mmol . 1~ ')
Low density lipoprotein
cholesterol (mmol . 1 ~ ' )
High density lipoprotein
cholesterol (mmol . ~ ' )
Triglycerides (mmol ~ ' )
Dietary fat intake (% kcal. day ~"')
Females
Mean (SD)
r
Mean (SD)
r
39-3 (12)
60-5 (6)
21 3 (4)
121 (11)
79 (9)
4-24 (1-4)
2-28 (0-7)
- 006*
007*
008*
016**
009*
008*
002
38-7 (11)
53-2 (7)
211 (4)
118 (10)
77 (8)
4 1 (12)
2-25 (0-6)
• 008*
008*
0-09*
015**
008*
007*
003
119 (012)
-003
1-22 (013)
•004
1 43 (0-6)
15-6 (3)
004
012**
003
011**
1-43 (0-6)
15 2 (3)
*/><0-05, **P<001.
Table 7 Age-adjusted odds ratios and confidence intervals for coronary artery
disease and prevalence of risk factors in relation to social class by logistic regression
Coronary artery disease
Hypercholesterolaemia
Hypertension
Smoking
Body mass index
Sedentary lifestyle
Males
Females
Odds ratio (95%
confidence
interval)
Odds ratio (95%
confidence
interval)
0-83
0-85
0-89
0-68
0 91
0-69
0 61
0-82
0-87
0-52
0-93
0-50
(0-66-0-95)**
(0-61-0-96)*
(0-64-0-99)*
(0-50-0-90)*
(0-82-1 11)*
(0-58-0-82)*
(0-42-0-81)*
(0-58-0-98)*
(0-63-0-95)*
(0-31-0-92)
(0-81-1-12)*
(0-31-0-88)
*/><005, **/ > <001.
people and people of low social class. Level of edu- ables were not reported in this study'121. More recently,
cation, income, occupation, employment status, indices Wander et al. and Gopinath et al. reported that the
of social class, measures of living conditions, area based prevalence of coronary disease was lowest in labourers
measures, life span measures and measures of income and highest in professionals and skilled workers'29'301.
inequality are widely considered measures of social One of these studies'301 also showed that the prevalence
class'1"51. Some experts'21 suggest that other than income was higher among literate than illiterate subjects which
or educational status, prestige of a particular job may be is against the observations reported by Gupta et a/.'121.
important.
Raman Kutty et al. from a South Indian suburban
Survotham and Berry'61 reported that coronary village, reported that coronary disease prevalence was
artery disease was more prevalent among high income highest in the higher socio-economic groups1"1. Howgroups without giving any explanation. Other workers ever, in all these studies detailed analysis of data to
emphasised that people engaged in physically demand- demonstrate the relationship of social class with coring work such as farming were less likely to develop onary disease were lacking. Studies from other developcoronary disease than people with sedentary occupa- ing countries have not analysed data according to
tions'7'81. In a recent study, Gupta et a/.'121 found that various attributes of social class'13141.
although illiterate and less educated people were more
We also observed that in the Indian Social Class
physically active, they had a higher prevalence of cor- and Heart Survey, higher body mass index, serum
onary disease. It is possible that illiterate and less cholesterol, triglycerides and blood pressure levels as
educated people in this study included mainly rich well as dietary fat intake were significantly associated
farmers who are known to consume a relatively higher with social classes 1 and 2. However, these levels of risk
fat diet. Smoking was also more common among factors and dietary fat intake are considered within
them'121. Dietary fat intake, income and consumer dur- desirable limits in developed countries (Table 5). These
Eur Heart J, Vol. 18, April 1997
594 R. B. Singh et al.
observations support the findings of the Seven Countries
Study'20' which showed that the 'risk' of risk factors may
be universal in different communities. However, the
force of each risk factor can vary depending upon
differences in biological risk factors and genetic factors.
This may explain differences in absolute risk'201. Higher
lipoprotein(a) levels, in utero under-nutrition, insulin
resistance and antioxidant vitamin deficiency may explain the cause of higher coronary risk even at relatively
low levels of conventional risk factors'31"381.
Studies from developed countries indicate that
low social class and poverty are major coronary risk
factors'1"51. It is possible that people in the higher
socio-economic strata of developed countries care for
their health by consuming low fat, high fruit and vegetable diets, smoke less and have more spare time
physical activity. In lower socio-economic groups, there
is higher consumption of animal foods, saturated fat and
sugar and less opportunity for spare time physical
activity, which predispose to higher coronary risk'281.
The situation is the reverse in developing countries
because people in the lower socio-economic strata are
too poor to buy animal foods, sugar and high fat foods
resulting in under-nutrition'15"191.
The Indian Social Class and Heart Survey has
shown that people in social classes 3 and 4 were consuming cereal-based very low fat diets (>13% kcal. day"').
The lower mean body mass index (19-6 kg. m~ 2 ) in
social class 4 indicates that the majority of these subjects
had a body mass index of < 18-5 kg . m ~ 2 , suggestive of
under-nutrition (Table 5). Multivariate analysis of our
data after inclusion of physical characteristics and smoking nullified the association of social class with the
prevalence of coronary disease. This indicates that
social class acts conjointly with other diet and lifestyle
characteristics in increasing the risk. Details of assessment of social class have been described.
The implications of the changing social class
pattern of coronary disease is that the characteristics
linking economic position to coronary disease may
change during the transition from poverty to affluence.
It seems that in most developing countries as socioeconomic development proceeds, coronary disease
increases. However, as in most developed countries,
further socio-economic development is associated with a
decline in coronary artery disease. It is as if coronary
disease passes through a community in a wave, affecting
first the more privileged and subsequently the less privileged. Prevalence declines first in those better of and
subsequently in the rest of the subjects'391. It is possible
that some Indian populations with a higher social class
may benefit by consuming a low fat diet, engaging in
more physical activity, ceasing smoking and decreasing
total and LDL cholesterol and triglycerides.
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