Hypvrtviutimt
Original Articles
Hypertension and Economic Activities in
Sao Paulo, Brazil
MYRIAM B. DEBERT RIBEIRO, M.D., ARTUR B. RIBEIRO, M.D., CARLOS STABILE N E T O , M.D.,
CARMEN C. CHAVES, M.D., CLAUDIO E. KATER, M.D., MAGID IUNES, M.D.,
MANOEL A. S. SARAGOCA, M.D., MARIA TERESA ZANELLA, M.D., MEIDE S. A N ^ A O , M.D.,
ODAIR MARSON, M.D., OSVALDO KOHLMANN J R . , M.D., ROBERTO J.S. FRANCO, M.D.,
SERGIO F. N U N E S , M.D., AND OSWALDO L. RAMOS, M.D.
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SUMMARY A study of the prevalence of hypertension was undertaken among workers in 10 subsectors of
the economy in Sao Paulo, a major urban-industrial area of Brazil. Included in the study were 5500 subjects
15-65 years of age, employed in 57 randomly selected firms. Hypertension rates (DBP ^ 90 mm Hg) were
higher among males up to 44 years of age. There was a decreasing gradient from mild to moderate and severe
forms in all groups. Severity tended to increase with age in all groups. Black males showed higher rates than
whites (29.2% vs 16.7%, p < 0.05), the excess being partially accounted for by moderate and severe forms
(40% vs 20%). Subjects who overworked showed a trend toward higher hypertension rates. Higher rates in four
subsectors (metallurgy, finance, transport, and journalism), aside from the distribution of known risk factors
and job selection, may reflect a variety of work-related stressors.
(Hypertension 3 (suppl II): II-233-II-237, 1981)
KEY WORDS
• hypertension
• occupational medicine • stress • ethnicity • work
O
VER the last 20 years, many epidemologic
studies have confirmed the importance of
hypertension as a precursor of cardiovascular morbidity and mortality.1"4 In most developed countries hypertension and associated diseases have been acknowledged as major public health
concerns. In underdeveloped countries, however, the
issue is much less clear. For a long time, health and
disease patterns in underdeveloped countries have
been considered to be altogether different from those
prevailing in developed societies. Evidence has accumulated in recent years, however, that shows at
least in some areas of the so-called "third world" a
mixed pattern of disease characterized by disorders
considered more prevalent among urban industrial
populations than in "traditional" societies.'
The transition from traditional to industrial
societies is a complex process involving profound
social and economic changes that, in turn influence
From the Departments of Preventive Medicine and Medicine
Escola Paulista de Medicina, S5o Paulo — Brazil
Drs. Myriam B. Debert Ribeiro and Artur B. Ribeiro are Established Investigators of the National Council for Technological and
Scientific Development (CNPq). Partial financial support was provided by FINEP
Address for reprints Myriam B Debert Ribeiro, M D , Assistant
Professor Epidemiology Division, Escola Paulista de Medicina,
Rua Botucatu, 720-04023, SSo Paulo, Brazil
11-233
health and disease patterns of the members of society.
In urban industrial societies, entry into the job market, qualitative aspects of work (time pressured,
hierarchically controlled, competitive) as well as the
quantity of work, have been argued to be critical
events regarding hypertension. 6
The objectives of the present study were to: 1) estimate the prevalence of hypertension among workers
in selected economic activities of a highly urbanized
area of the third world, the Metropolitan area of Sao
Paulo; 2) provide descriptive data on the epidemiology of hypertension in that population; and 3)
set up baseline data for testing hypotheses relating to
work-related factors associated with hypertension.
Methodology
Subjects from 10 subsectors of the economy were
studied. In the secondary sector (industry), the following subsectors were selected: textile, metallurgy, housing, and automobile construction. In the tertiary sector (trade and services) the selected subsectors were
the following: trade (wholesale, retail), insurance,
loans and finance, transportation, advertising and
journalism, teaching, liberal arts professionals.
In Brazil, a federal law, known as the "Law of the
Two Thirds," makes it mandatory for each firm to
report annually to the Ministry of Labour the number
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PROCEEDINGS/INTERAMERICAN SOCIETY
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of its employees. The 1976 report of the law provided
the sampling universe for the present study. Firms
were classified by number of employees as small
(50-99 employees), medium (100-499), and large ( £
500 employees). The number of firms in the sample
frame totalled 3122, from which 1601 were small,
1289 medium, and 232 large firms and included an estimated population of 760,000 workers.
In each of the three strata, 20 firms were randomly
selected. The sample was further stratified according
to subsector of the economy. In each subsector, six
firms were selected: two small, two medium, and two
large. In addition to the list of randomly selected
firms, a replacement list following the same procedures included one firm for each subsector. There
were 57 of the 60 planned firms included in the sample:
17 small, 21 medium, and 19 large. Three firms were
not included in the study due to time-table constraints.
Each firm selected for the study was visited by a
member of the medical team, in order to obtain the
consent and participation of the management. Once
given the consent, an updated list of workers was obtained. The number of subjects to be examined in each
firm varied according to its size: 50 to 80 subjects were
examined in small firms, 80 to 100 medium, and 100
to 150 in large ones. Subjects in each firm were randomly selected for the study using a table of random
numbers; 5500 subjects of both sexes aged 15 to 65
years were included. Selected employees seldom
refused to participate (10 subjects). Replacements
were random selected to make up for possible
absentees; an additional list of 10% of the number of
employees was used for that purpose. Absentees included not only those currently working at the firm
and not present at the visit, but also people who had
been dismissed or had resigned.
Project interviewers (doctors and medical students)
were trained to administer survey questionnaires. The
training time included closed sessions with the supervisor, field visits to two firms, and comparison of
blood pressure measurements of hospitalized patients
taken by the interviewers and recordings from an
Arteriosonde instrument (Roche Instruments).
Information was gathered on age, sex, ethnicity,
and weekly working hours. Subjects were kept in the
TABLE 1. Mean Diastolic Blood Pressure (DBP) AccordFemales
Males
Age
DBP
(n)
(y«) (mm Hg) SD
15-24
714
11.4 (1237)
25-34
12 4 (1442)
78 0
35-44 84.0
(796)
14.0
45-54
13 7 (405)
86.0
55 + 90.5
15 5
(133)
DBP
(mm Hg)
SD
(n)
69.1
72.4
79.5
842
82.6
10.3
10 9
12.6
13 0
14.2
(696)
(517)
(179)
(54)
(11)
Total sample = 5470 (4013 males, and 1457 females) SD =
standard deviation; n = number of observations.
SUPP
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sitting position for 10 minutes, and blood pressure was
measured by the team doctor with a mercury
sphygmomanometer on three consecutive times.
Phases I and V of Korotkoff sounds were recorded.
Cuff dimensions were 13 X 30 cm. Blood pressure
measurements were taken by 11 interviewers.
Hypertension was considered to be present when the
mean of the three diastolic blood pressure readings
was equal to or greater than 90 mm Hg. The dependent variable was further refined into three degrees of
severity: mild (90-104 mm Hg), moderate (105-119
mm Hg), and severe (^ 120 mm Hg). Results are also
expressed as mean diastolic blood pressure, and x 2
tests and normal difference test between proportions
were used to assess statistical significance.
Results
The mean of diastolic blood pressure levels and
sample composition according to age group and sex is
shown in table 1. Male subjects constituted the majority of our studied sample (76%). Younger agegroups were overrepresented: 86.6% of males and
95.6% of females were less than 45 years of age.
The prevalence of hypertension (table 2) was 18.1%
for males and 6.6% for females. Differences between
the sexes were significant up to 44 years of age (p <
0.001). For both sexes, hypertension rates increased
with age. These increments were significant for all
groups except for women 45 years and over.
Figures 1 and 2 show the distribution of mild,
moderate, and severe cases of hypertension by age and
sex. For both sexes in all age groups there was a
decreasing gradient from mild to moderate and severe
forms. Mild and moderate forms increased with age
for both males and females. Severe forms increased
with age among males and were absent in all but one
group in females (45-54 years).
Figure 3 depicts hypertension rates according to
ethnicity. Rates of diastolic blood pressure ^ 90 mm
Hg were almost twice as great in black as in white
males (29.2% vs 16.7% respectively,/; < 0.05). Black
and mulatto females showed a greater incidence of
hypertension compared to whites, but the differences
were not significant.
TABLE 2.
Prevalence of Hypertension
by Age and Sex
(90% Confidence Intervals, Cl)
Age
(yrs)
15-24
25-34
35-44
45-54
55 +
Total
Males
%
53
15 7
29 5
33.6
46.7
18.1
(90% CD
(4.3-6 3)*
(14 2-17.2)**
(26.9-32 1)*
(29.8-37.4)NS
(39.7-53.7)NS
(17.1-19.1)**
Females
%
2.7
5.6
17.8
24.1
27.3
66
(90% CI)
(1.7-3.7)
(4.0-7 2)
(13.2-22.4)
(14 6-33 6)
(5 4-49 2)
(5 6-7.6)
*p < 0.01; **p < 0.001. NS = not significant (males vs
females for normal difference in each age group).
HYPERTENSION AND ECONOMIC ACTIVITIES/Ribeiro
x
et al.
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30
40 -i
Mi - Mild
M l - Mild
Mo-Moderate
Se -Sev«r«
Mo - Moderate
Se - Severe
30 20
20 •
10 •
10
Ml
Mo S .
13 >
1 24yr
Mi
25
Mo S t
|
1
34yr
Mo S«
Mi
33 i
1 44yr
Ml Mo S .
45 '
1 54yr
Mi
Mo Sa
55 + yr
Mi
Bi
Mo Se
1 24
Ml
251
Mo Sa
|134
Ml
35 •
Mo S«
<44
Ml
Mo Se
154
451
Mi
Mo S«
55 +
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FIGURE 1. Hypertension rates for males, by age groups
and degree of severity. Mild (Mi) = 90-104 mm Hg;
moderate (Mo) = 105-119 mm Hg; severe (Se) = 2: 120
mm Hg).
FIGURE 2. Hypertension rates for females by age groups
and degree of severity. Mild (Mi) = 90-104 mm Hg),
moderate (Mo) = 105-119 mm Hg; severe (Se) = £ 120
mm Hg).
In each particular age group, for both men and
women, we compared the hypertension rates of those
working more than the median weekly hours (men =
48.0 hours and women = 42.3 hours) to those working
less than that median; we observed that for all groups
except for men 25-34 years) the prevalence of
hypertension was greater in those subjects working
more than the median. In none of the groups,
however, did the differences between rates reach
statistical significance. Nevertheless, a borderline significance was observed in women of 45 years and over
( X J = 2.06, 1) (fig. 4).
Age-sex standardized rates (indirect method) by
subsector of the economy arc shown in table 3. In four
subsectors (metallurgy, insurance loans and finance
transportation, and advertising and journalism) the
rates were higher than the overall figure for the population studied (15.0%).
Discussion
The Metropolitan area of S3o Paulo, with a population of approximately 13 million (11% of the country's
population), is the main urban and industrial center in
(X)
(n-199)
*~~< < median
> median
30 -
ln-2588)
(n-189)
In-1032)
15 -
(n-230)
60 •
ln-1079)
M
F
whites
10 In-33)
M06)
M
F
orientals
3-
M
F
mulatos
M
F
blocks
Sex
ethnic group
M F
\5—i24
M
F
251—134
M
F
35 >— 4 4
M
F
45 +
Sex
age group
(yean)
FIGURE 3. Hypertension rates (DBP 2: 90 mm Hg) according to ethnicity in males and females.
FIGURE 4. Age-sex specific hypertension rates in subjects
working more (straight line), or less (broken line) than median values of weekly working hours. Median values = 48.0
hours for males and 42.3 hours for females.
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PROCEEDINGS/INTERAMERICAN SOCIETY
TABLE 3. Hypertension Rates in 10 Selected Subsectors of
the Economy
SubBector
Textile
Metallurgy
Automobile construction
Housing
Trade
Insurance, loans & finance
Transportation
Advertising & journalism
Teaching
Professionals
Rate(%)
12.9
17.3
11.4
13.9
12.1
18.6
18.9
21.0
13.9
11.0
Age-sex standardized rates were used (indirect method).
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Brazil, beginning in the 1930s. The area represents the
most dynamic center of the country's economy, attracting migrants from the state of S§o Paulo and
other states in their search for jobs and an improved
standard of living. In regard to health indicators, infant mortality rate is 80% of the live births, and infectious diseases and protein-caloric malnutrition still account for a large proportion of deaths in the first years
of life. As the preceding results show, in the
metropolitan area of SSo Paulo among those engaged
in economic activities, hypertension represents an important health problem.
Age-specific rates as well as the increase in blood
pressure levels with age are in agreement with figures
reported in Western industrial societies.' The present
findings must be interpreted with the nature of the
studied population in mind, including some specific
features involving the entry, permanence, and dropout
of workers from the job market in the area. Women
participate much less in economic activities than men,
as reflected by the composition of our randomly
selected sample, and although work participation
decreases with age for both sexes, the decline is particularly sharp for women 45 years and over, based on
life tables in our area. In particular, the dropout rate
of women from the labor force is significantly higher
than that of men,* not only because of marriage and
childbearing, but also because of illness. Male-female
differentials in dropout rates resulting from hypertension and associated diseases might thus amplify the
difference between the sexes. Evidence that would
possibly support this hypothesis is provided by the absence of severe forms of hypertension among women
in all but one group, although true sex-differences
regarding the course and natural history of the disease
cannot be ruled out.
On the other hand, entry of women into the job
market is possibly influenced by several attributes, including their disposition to compete for a limited
number of jobs and the selection standards used by
employers. Although our study did not address these
questions, it seems likely that in such a context women
who acknowledge their hypertensive condition would
tend to fulfill job vacancies less than men.
SUPP
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1981
In regard to ethnicity, the higher rates observed
among black males agree with those derived from
blood pressure studies in the U.S. and the Bahamas
showing that by age 20, blacks already have higher
blood pressure than whites.*"11 It is noteworthy that
the excess hypertension in black males in our sample is
partially accounted for by moderate and severe forms
(40% in black males vs 20% in white males). Black females show an increased prevalence when compared
to whites, although significance levels were not
reached, possibly due to the small number of black
women in the sample.
A central concern in our present study was to search
for an association between hypertension and the
number of working hours. The observed trend, in all
groups, of an increased prevalence of hypertension
among those who overwork certainly deserves further
attention. Although apparently large differences in
rates for women 45 years and over were observed, the
number of women in this group was small and significance was not reached. In the present analysis,
body mass index was not taken into account. The
available data on the Quetelet index for males shows
that it increases with income whereas the opposite
direction is found among females. On the other hand,
the correlation between income and blood pressure
among females is very small (r = —0.03 for females
and 0.18 for males). Given the complex interrelations
among body mass index, income, and working hours,
it is possible that the association between working
hours and blood pressure levels among women may be
reduced when control for body mass is introduced.
Due to the cross-sectional nature of the present study
and its limited knowledge of the time-order of the two
variables, the data might still suggest that overwork
may render certain individuals more vulnerable to
hypertension. Older women in the sample represent a
special group that often accumulates social roles such
as head of household, housewife, and wage worker.
Conflictive demands in the job as well as in private and
community life, coupled with increasing age and
biological change, might help to explain increased
blood pressure levels in those who overwork. At any
rate, the hypothesis is worth testing in specially
designed studies.
Four of the 10 selected economic activities, namely,
metallurgy, insurance andfinance,transportation, and
journalism showed higher than average rates of
hypertension. Observed differences in rates might be
due to the tendency of some interviewers to read blood
pressure higher or lower than others. Analysis of available data on blood pressure measurements (obtained
in the pilot study and from hospitalized patients),
however, did not reveal any systematic interobserver
variation. Thus, it is unlikely that differences among
interviewers might account for the observed differences. A possible confounding variable that might explain differences in the prevalence of hypertension is
represented by body mass index. Analysis of mean
Quetelet index, controlled for age and sex, however,
showed that differences in the index can account for
only a small part of the variation in hypertension
HYPERTENSION AND ECONOMIC ACTIVITIES/fl/6ej>o et al.
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rates. It is noteworthy that transportation, communication, and financial services reflect growing material production and are pivotal to the modernization process. Higher rates in these subsectors, aside
from the distribution of known risk factors and job
selection, may reflect a variety of environmental
stressors.
These findings are difficult to compare with those of
other studies since morbidity surveys have been based
on the general population18 or relatively homogeneous segments of it in terms of economic activity.1'
However, it is tempting to speculate that physical
agents such as heat and noise (metallurgy), timepressured and highly competitive work (journalism),
socially controlled activities (finance),14 and the disparity between growing demand and limited availability of certain services in the metropolitan area
(transportation) may represent, among other factors,
important sources of socially induced stress.
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Hypertension and economic activities in São Paulo, Brazil.
M B Ribeiro, A B Ribeiro, C S Neto, C C Chaves, C E Kater, M Iunes, M A Saragoça, M T
Zanella, M S Anção, O Marson, O Kohlmann, Jr, R J Franco, S F Nunes and O L Ramos
Hypertension. 1981;3:II-233
doi: 10.1161/01.HYP.3.6_Pt_2.II-233
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