Document JLRzMXjknpob4bKy9Er8VoBv

- AR RG _ 1496 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 enployees at the Washington Works Plant from 1956 to 1973. br. 3 Power, Plant Physician, requested the investigation because some workers had complained that the occurrence of heart attacks among employees seemed excessive. DESIGN AMD METHODS A computer search of the morbidity files in Wilmington J produced a list of cases for this retrospective study. A case it go E defined as any male employee who suffered a first myocardial in- BsEg 7Boifsarctiaosnsin(t4r.i1.o)n bsenttwueteensJarneuvaoornye1,vie185r6e,vovaenrdedDecfeoumnberan 31a,vte1n973A.LT. s and those who died suddenly from coronary heart disease. Persons Who had lefe work for any reason were considered potential propos during only those years in the study period when they were active : employees. Females were excluded from the study, as they represc a group too small in size for statistical analysis. Additional data concerning plant population statistics and occupational profiles for each case were obtained from recor at Washington Works. Sixty-one cases of M.1. wee observed during the eight: year period. A breakdown by age categorization within three-yea periods for salary roll and for wage roll hen is presented in Tarte 1 000003 CONTAIN No cg DUPONT 910 -2Age-specific Du Pont Company rates for male wage roi and salaried personnel were used to compute the expected number of M.I.'s at Washington Works. Again, three-year time periods were selected for this determination. It would not have been sufficient to have referred to the 1973 figures, nor to have averaged or otherwise agsresated 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 number of myocardial infarctions at Washington Works : and the number of cases predicted according to Company statistics are presented in Table III for wage roll and for salary roll employees. MALsTS No excess incidence of M.I. is evident among the male wage roll employees. The expected number of M.I.'s is 34.0; 32 were observed. One notices that the number of cases has been increasing over the years at Washington Works. One suggested explar tion is that with an increasing percentage of employees over the age of fifty, both at Washington Works Plant and in the Company (Table 1), more M.I.'s are to be expected. Among salaried employees, the observed incidence of myocardial infarction is significantly higher than the expected number, under the assumption that cases follow a Poisson distribution: 25.M.I.'s were observed; 21.5 is the expected nunber (Pac 06). The high overall incidence is largely the result of elevated rates in recent years. In.the period from 1971 to 1973, the difference between observed and predicted numbers is great DUPONT911 000004 ee I. -- EE-------------------- 12 observed cases versus 5.3 expected cases (P = 0.008) whereas in the preceeding years no differences between observed and ex- pected nusbers 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 among the population of foremen at Washington Works: were mechanical foremen, 9 were production foremen, 2 were laboratory foremen, and 1 was a yird and transportation foreman. Approximately thirty-fivepercent of the salaried men at the plant are foremen. Since the age distribution of foremen is comparable to that of all 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. The foremen studied range in age at onset of the attack from 35 to 65 years. Both the mean and the median number of years of experience as foremen prior to M.I. is 9.0. The range is 1 week to 25 years. Patrolmen, a group representingthreepercent of the Washington Works population, also showed a somewhat elevated incidence of M.I. Four cases were observed among patrolmen, whereas the expected number is 1.4 (33 of 29). The age at onset for these patrolmen, 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 patrolnen Distribution of M.X: cases among employee work classifications is presented in Table v. DUPONT 912 000005 CE ---------- --asumrry 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 vas found that no excess of M.I. cases occurred among wage roll persons whereas anong 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 cofonary 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 a company-wide investigation of morbidity among foremen. esa TT ey MBAlUoRsEtEaNtiTs.tic0i'aBnERG DUPONT 913 000006 TABLE 1 AGE DISTRIBUTION OF M.I. CASES BY THREE-YEAR PERIODS AT WASHINGTON WORKS, 1956-1973 Age 1956-58 *195M9a-l6e1 Wag1e962(-N6u4mber 1o9f65-E6m7ploye1e9s68-70 1971-73 Tora. 20 o 20-24 1 1 25-29 30-34 2 2 35-39 2 : 3 1 5 0-44 2 1 3 45-49 1 1 2 3 1 5 s0-54 1 1 3 1 6 55-59 _a 3 4 60-64 2 2 Total 1 s a. 6 5 7 32 Age 1956-58 195M9a-l6e1 Sal1a9r6y2-6(4wumb1er96o5f-67Emplo1y9e6e8s-:70 1971-73 Tota 20 - o 20-24 o 25-29 o 30-34 1 1 35-39 1 a 1 10-44 1 2 3 15-49 3 2 1 5 50-54 1 1 2 1 2 7 55-59 1 1 1 7 10 50-64 1 1 rotal 0 s 3 4 s 12 29 DUPONT 914 000007 CE -- mame 1x Age-SpPeecrif1i0c0,0D0u0,PonOft CMoImpCaansyesRates, Age | 20-2204 3205--3249 1305--4349 5405--5449 5605--6549 *roTAL 1956-58 | 00..00 184.06 17883..27 4780471.79 898430..38 280 WAGE - MEN 1959-61| 1962-64| 1965-67| 00.l00 00l.o0 2100.30 364.40 12872.077 2115440.69 388142..01|| 365380.047 991602.53|| 7e1s31a8 357 259 50..10 10a026 15150.28| 368754..44| 899859..97 || 267 1968-70 | 1971-73 1200.40 00.l00 11150.78 oilso 214120s0 J8E6.N2 3576250.93 464282..25 1,9016340.69 | 1,186094..48 275 21 SALARY - MEN A 1956-58| 1959-61| 1962-64| 1965-67| 1968-70| 1971-73 20-2204 3205--3249 2305--1349 5405--5149 6505--6549 || 00..00 60.02 24577..29 710538..97 11,,302071..90 | 00l.00 1o3l80 18844.l40 6458131071 | 1,0900370.31|| 00l.o0 560.l40 26387..87 5455020.73 1,9136651.76 | 00..00 80l30 117159..29 6344250.75 | 1,804294..82 | 00..00 77..06 24036'.4 a3s12s0i4s 1,174716.l50 00.l00 200.005 6409 138403.40 7470670.20 -- 97205 TOTAL 354 330 331 303 211 215 *Age-adjusted rate DUPONT915 000008 -------------------- TABLE IIT OBSERVED NUMBER OF M.I. CASES AT WASHINGTON WORKS AND EXPECTED NUMBER OF M.I. CASES, BASED ON DU PONT COMPANY MORBIDITY Hale wage 195658 1959-61 196264 1965-67 1969-70 19m-73 1c Observed 1 6 a 5 8 7 : Expected 2.2 3.8 9 6.0 8.2 8.9 : 16:58 as Male salary : lagee lesser 13Een umn me Observed 0. 5. Expected 15 2.5 34 "a0 57 12 0 2 3s 3.9 1.8 5.3 : DUPONT916 000009 TABLE V OABNDSEREVXEPDECTNEUDMBENRUMBOEFRMO.IF. M.CTA.SESCASBEYS,OCCBUASPEADTIOONN OCWCOURPKAST,IONMAALLEDISSATLRAIRBIUEDTIOENMPLATOYEWEASSHINGTON occupaTION Foremen Supervision through - Management specialists Analysts, Accountants Engineers Clerical Patrolmen Draftsmen TOTAL % EMOFPLOSYAELEASRIAETD WASHINGTON WORKS 358 OBSERVED OF NUM.MIB.E'RS 20 23 3 2 1 n 228 108 o 3 4 2 Loa 25 EXPECTED OFNUMM.IB.E'RS* 10.2 6.7 14 9 6.4 2.9 9 1.4 "expected umber = % x 29 DUPONT918 000010