Document a1gw1pgk951xqOBJzjM71XJDy
AR226- | HHE
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STUDY OF MYOCARDIAL INFARCTION AT WASHINGTON WORKS PLANT
This study was conducted to evaluate the incidence of cases of myocardial infarction among male wage and salary roll employees at the Washington Works Plant from 1956 to 1973. pr. v. 3 Pover, Plant Physician, requested the investigation because some workers had complained that the occurrence of heart attacks among employees seemed excessive.
DESIGN AND METHODS
A computer search of the morbidity files in Wilmington
produced a list of cases for this retrospective study. A case is
defined as any male employee who suffered a first myocardial in
farction (M.1.) between January 1, 1956, and December 31, 1873.
This definition includes persons who recovered from an acute M.I.
and those who died suddenly from coronary heart disease. Persons
who had left work for any reason were considered potential propositi
during only those years in the study period when they were active
employees. Females were excluded from the study, as they represent
a group too small in size for statistical analysis.
Additional data concerning plant population statistics
and occupational profiles for each case were obtained from records
at Washington Works.
Sixty-one cases of N.I. wehe observed during the eighteen-
vear period. A breakdown by age categorization within three-year
periods for salary roll and for wage roll hen is presented in
Table 1.
00sL0See
.
2.
.
Age-specific Du Font Company rates for male wage roi1
and salaried personnel were used to compute the expected number
Of M.I.'S at Washington Works. Again, three-year time periods vere selected for this determination. It would not have been
sufficient to have referred to the 1973 figures, nor to have averaged or otherwise aggregated the rates over the eighteen years,
because a trend toward lower incidence in the Du Pont Company has occurred in recent years. The Company rates are shown in Table II.
The observed nunber of myocardial infarctions at Washington Works and the number of cases predicted according to Company statistics
eamrpelopyreeesse.nted in Table IIT for wage roll and for salary roll
ANALYSTS
vase
roll
No excess incidence of M.I. is evident among
employees. The expected number of M.I.'s is
the male
34.0; 32
vere observed. One notices that the number of cases has been increasing over the years at Washington Works. One suggested explana-
thon is that with an increasing percentage of employees over the ade of fifty, both at Washington Works Plant and in the Company
(Table IV), more M.I.'s are to be expected.
Among salaried employees, the observed incidence of
mnuymobcearr,diaulndeirnftahrectiasosnumipstisoingntihfaitcacnatsleys hfioglhleorwthaaPnoitshseonexdpiescttreid-
bution: 28.M.I.'s were observed; 21.5 is the expected mumber (P22 -06). The high overall incidence is largely the result of
elevated rates in recent years. Inthe period from 1971 to 1973, m
a
8
-
000091
.
3a
:
12 observed cases versus 5.3 expected cases ( = 0.008) whereas
in the preceeding years no differences between observed and ex-
pected numbers were significant. (P> .10 for all comparisons).
Further investigation of occupation reveals that the high frequency of M.I. cases among salaried employees is seen
largely in foremen. Twenty of the twenty-nine cases occurred
anong the population of foremen at Washington Works: 8 were
mechanical foremen, 9 were production foremen, 2 were laboratory
foremen, and 1 was a yard and transportation foreman. } thirty-five percent of the salaried men at the plant
Approximately
Since
the
age
distribution
of
foremen
is
comparable
are foremen. to that of ail
salaried employees at Washington Works, one would expect that only 10 Of the observed M.I.'s would present in this occupational class
(35% of 29), compared to the 20 which occurred among foremen.
he foremen studied range in age at onset of the attack from 35 to 65 years. Both the mean and the median number of
iysea1rsweoefketxope2r5ienyecaersa.s foremen prior to M.I. is 9.0. ne range
Patrolmen, a group representing threepercent of the Washington Works population, also showed a somewhat elevated. in-
idence of M.I. Four cases were observed among patrolmen, whereas the expected number is.1.4 (3% of 29). The age at onset for these
patrolnen, however, ranges from 55-59 years; this-is older than the median age at onset for the entire group, which is about 50 years.
This consideration explains the increased incidence among patrolmen. Distribution of M.I: cases among employee work classificationsis
Presented in Table v.
:
.
.
S &
.
3
000092
.
.
i summary
This study examines incidence of myocardial infarction among male employees at Washington Works over an eighteen-year period. Using Du Pont Company rates as the referrent, it was found that no excess of M.I. cases occurred among wage roll persons, whereas among salaried men, elevated morbidity rates obtain. The target group among salaried employees is foremen. Increased incidence in this group cannot be explained by their age distribution. One asks, then, if some aspect of the work routine is a causal link in the development of coronary heart disease, or if some personal characteristic which predisposes one to become a foreman is a risk indicator for M.I. As a result of the findings of this study, the/ Biostatistics Group in Wilmington will explore the possibilityotf a Company-wide investigation of morbidity among foremen.
oy
tained T- 0
MBAiUoRsEtEaNtisT.ticOi'aBnERG
.
r
keK2; &&
000093
E-- T ------
|
Age 20
20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64
Total
Age 20 20-24 25-29 30-34 35-39 10-44 5-49 50-54 55-59 60--_---6_4-- Total
TABLE I AGE DISTRIBUTION OF M.I. CASES BY THREE-YEAR
PERIODS AT WASHINGTON WORKS, 1956-1973
1956-50
1 1 1956-58
4
0
195M9a-l6e1 Wag1e962(-N6u4mber19of65-E6m7ploye1e9s6)8-70 .
1
2
2
3
2
1
1
1
2
3
1
3
1
_1
6
1
6
8
195M9a-6l1e Sal1a96r2y-6(4Numb1e9r65of-67Emplo1y9e6e8s-)70 -
1
1
1
3
2
1
1
2
1
1
.1
1
A1
5
3
4
5
1971-73
1 1 3 2 7
gota: 0 1 0 2 6 3 8 6 4 2
32
1971-73 Total
0
0
0
1
1
2
3
1
6
2 z
7. o
7
10 g
a
1 @u
12
29
coogi
TABLE IT
.
Age-SpPeecrif1i00c,0D0u0,Poonft MCIomCpaasneysRates,
WAGE - MEN
Age | 1956-56| 1959-61| 1962-64| 1965-67 | 1968-70 | 1971-73 #
20-2204 [03.0 3205--3249 1840060
o0l.o0 0.0
00l.00 6.0
50..10 102.004 a2 107
00l.o0 als
35-39
40-44
88.7
178.2
45-49 | 484.7
21170.37 | 13144064 238824.07| 3255840.49
1550..85
19102
11510g8
242.0
806l20
183.6 *4X
5550--5594 || 8780371.39 60-64 | 940.8
981622.s1 || 761330.78 | 910.3 | 857.4 |
637845..44 || 895.9 |
336752.039 | 464282.i25 91505 | so04.4
989.7| 1,064.5 | 1,169.
g4e7s
"roman| 280
357
259
267
275
8 mn
SALARY - MEN
Age | 1956-50| 1959-61| 1962-64| 1965-67| 1068-70| 1571-73
20-2204 3205--3249
00l.00 00
l0.o0
00..00
0.0 000
00..00
00l.00
0l0 7.0
00l.00 0.0
35-39 576..92 - 1a0s--2u4s|| 2a4s7al.72
18340.80 184.4 |
5668..48 | 23707 |
11980.53 17502|
4370.56 206.4
as17 |
2640..95 18000
5550--5594 60-64
|| |
1,070013.009 1,327.9
|
1,060873..11||
545520.037 || 9367 |
36a425l17s|| masis|
903.3| 1,165.6 | 1,024.2|
3s1s0a.9 | 1,1147160.05||
a37463.45-- Josie
sroman | 354
330
331
303
2m
975.8 215
*Age-adjusted rate
:
n
&33S
@
000095
8
TABLE IIT
:
OBSERVED NUMBER OF M.I. Cass ap WASHINGTON WORKS AND EXPECTED NUMBER OF m.r.cases
Bi
BASED ON DU PONT COMPANY MORBIDITY ,
Male Wage
Observed
1956-58 1
1959-61 6
1962-64
1965.47
1968-70
1971-73
gor,
Expected
2.2
3.8
1 4.9
6 6.0
8 8.2
7
32
8.9 34.
1956-58
1959-61
MaleSalary
:
1962-64 1065-67 1968-70
`1971-73
OEbxspeercvteedd 105. 2.55. 33s4 34s00 4.5813 51.23 yz m2p2o19g.a5;
- I 3 s g 8 000096
Age <25500 2250
TABLE Iv Du PoAngte CCaotmepgaonryizaantdiWoanshoifngMtaolne WEomrpklso,yee1s956a-t1973
WAGE ADNUDPSOANTLARCYOMPCAOMNBYINED*
1956-58 | 1959-61 | 1962-64 [1965-67 | 1068-70 | 1071-75
2H 03.T 712| | 14891,,713432 ||
18%
22%
1s886.,045113 218
|| 2"0657,.151600||
19773,.925579 |
118333,a4a4t1
258
27%
29%
Age "2 5500 8 250
1956-58| 3,136 151 a
WAGEWAANSDHISNAGLTAORNYWCOORMKSBINED*
1959-611 1962-64| 1965-67]
4,421 322
45.7212]
5,528] 744]
7%
108
12
1968-70 | 16,,030700
14s
1971-73 16,,202351 17%
"pBoapcuhlantuimobnerfroreprtehseentthsreet-hyeeacrumpuelraitoidv.e mid-year
g :
-
goS
8
000097
TABLE Vv
PNO5OCCEEWCXYOUREEPKEDASCT,TINEOUMNDMAABLLNEEORDNISOSEFTRRMI.OIBF.UTM.ICTOA.NSEACSTasBtWYsa.tocrhcmueopmrasoryzoohn SALARIED EMPLOYEES
o occur parIonm Foremen SuMpaenravgiesmieonnt through Specialists Analysts, Accountants Engineers Clerical
Patrolmen
Draftsmen TOTAL
BMAe,SEHOHMMFIPNNLGOGSIYAIOELONEANSRWIvOAEoRTDmKsS 35%
Cam 2 3x 228
108
3
2
ONBUSMEBREVRED oOrF wM.iT.r'sy
20
3 1 0 0 0
4
1 29
ExNeummcpTpEgD ooFp'byoEtRiRgs
10.2
6.7 1.4 .9 6.4 2.9
.9
1.4
*expected umber = 1 x 29
.. .
og
28
000098
&