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To explore possible explanations for elevated mortality from diabetes among male garment manufacturers and repairers in England and Wales during 1979-1990, we extended analysis by 10 years, looking also at other textile workers and at deaths from ischaemic heart disease (IHD).
We used data on some 3.5 million deaths to compute proportional mortality ratios (PMRs) for diabetes and IHD, standardised for age and social class, in 10 job groups concerned with manufacture of, or work with, textiles. For 1993-2000, we carried out additional analyses by place of birth.
Among men, mortality from diabetes was elevated in nine of the 10 textile job groups, with overall PMRs of 147 (95%CI 131-165) during 1979-90 and 170 (95%CI 144-199) during 1991-2000. Proportional mortality from IHD was also consistently high, although to a lesser extent. In female textile workers, mortality from both diseases was close to that for other occupations. In both sexes, mortality from diabetes and IHD was increased among people born in the Indian sub-continent (PMRs 353 and 139 in men; 262 and 130 in women). In men, the proportion of deceased textile workers who had been born in the Indian sub-continent (11.4%) was much higher than for all occupations (1.8%), but there was no similar differential for women (1.1% v 0.7%). When PMRs for male textile workers were standardised for place of birth, they were lower, but still significantly elevated (133, 95% CI 110-159 for diabetes and 109, 95% CI 105-114 for IHD).
There is no obvious occupational hazard that could explain an increased risk across such a wide range of textile occupations that is specific to men. One possible explanation is uncontrolled residual confounding related to place of birth. This could be tested through suitably designed morbidity surveys.
Analysis of occupational mortality in England and Wales for the period 1979-80 and 1982-90 indicated an unusually high proportion of deaths from diabetes among men employed in the manufacture and repair of garments . The excess mortality did not extend to women in the same jobs, and it was hypothesised that it might have occurred because the occupations concerned included a high proportion of immigrants from the Indian sub-continent, among whom the prevalence of diabetes is known to be elevated . Other possible explanations could be chance or an unrecognised occupational hazard in the clothing industry.
Data have now become available for a further 10-year period from 1991 to 2000, and we have used this new information to explore in more detail the risk of death from diabetes in garment and textile workers, and also from ischaemic heart disease (IHD), which like diabetes is more common in immigrants from the Indian subcontinent . In particular, we aimed to assess whether there might be an occupational hazard of diabetes in garment and textile workers.
The Office for National Statistics (previously the Office of Population Censuses and Surveys) provided us with data abstracted from death certificates on all deaths in England and Wales during 1979-80 and 1982-90 (at ages 20-74 years) and 1991-2000 (at ages 16-74 years). For each death we were given the sex, age, year of death and last full-time occupation of the decedent, together with the underlying cause of death coded to the ninth revision of the International Classification of Diseases (ICD 9). Occupations for deaths during 1979-1990 were coded to the 1980 OPCS classification , and those during 1991-2000 to the 1990 Standard Occupational Classification . From these occupational classifications, we defined larger job groups [1,6], of which 10 (listed in Table 1) related to textiles or fabrics. Social class, classified to six main strata, was derived from the decedent’s occupation by standard algorithms . For the years 1993-2000, we were also given the place of birth of the decedent, which for the purposes of this report was classified as UK, Indian sub-continent or “other”.
Analysis was based on deaths for which there was a reported occupation (1,564,981 men in 1979-80 and 1982-90, and 1,202,888 in 1991-2000; 322,775 women in 1979-80 and 1982-90, and 408,152 in 1991-2000), and focused on the relation of occupation to death from diabetes (ICD9 250) and IHD (ICD9 410-414). Associations were characterised by sex-specific proportional mortality ratios (PMRs), which were expressed as percentages and standardised for age and social class, with confidence intervals (CIs) based on the Poisson distribution. Some PMRs were additionally standardised for place of birth.
Among all male textile and fabric workers combined, there were 291 deaths from diabetes during 1979-90 (PMR 147, 95%CI 131-165) and 154 during 1991-2000 (PMR 170, 95%CI 144-199). As shown in Table 1, elevations of risk were observed consistently for all of the component job groups except knitters and clothing cutters. The highest PMRs were in spinners and winders (182 and 252), tailors and dressmakers (215 and 235) and sewers and embroiderers (192 and 197).
As a group, male textile and fabric workers also had significantly, although less markedly, increased proportional mortality from IHD, with PMRs of 111 (95%CI 109-113) in 1979-90 and 113 (95%CI 108-117) in 1991-2000. Again, the excess applied to almost all component job groups, the one exception being bleachers, dyers and finishers during 1979-90 (Table 1). However, the highest PMR (in sewers and embroiderers during 1991-2000) was only 128. The most consistent elevations of PMR were in spinners and winders, weavers and “other textile workers”.
In female textile and fabric workers, patterns of mortality from diabetes and IHD were less remarkable (Table 2). The overall PMR for diabetes during 1991-2000 was 111 (95%CI 98-126) based on 248 deaths, but in 1979-90 it was only 84 (95%CI 75-94). Moreover, none of the three job groups with the highest PMRs in men had a PMR in women in either period that was greater than 115. PMRs for IHD were significantly increased in 1979-90, but in 1991-2000, the elevation was marginal (PMR 103). As in men, job groups that consistently had the highest PMRs were spinners and winders, weavers and “other textile workers”.
Table 3 shows PMRs for men and women (all occupations combined) during 1993-2000 according to place of birth. In both sexes, mortality from diabetes was substantially elevated among people born in the Indian sub-continent (PMR 353, 95%CI 326-380 for men and PMR 262, 95%CI 196-342 for women). PMRs for IHD were also increased in people born in the Indian sub-continent, although to a lesser extent (139 in men and 130 in women). During the same period, the proportion of deceased male textile and fabric workers who had been born in the Indian sub-continent (11.4%) was much higher than for all occupations (1.8%). However, there was no similar differential for women (1.1% v 0.7%).
Table 4 shows PMRs for diabetes and IHD in textile and fabric workers during 1993-2000, stratified by place of birth. In men, mortality was elevated for both diseases in each of the three place of birth groups examined, although standardisation for place of birth as well as age and social class gave lower PMRs than in Table 1 (133 for diabetes and 109 for IHD). In women, PMRs after additional adjustment for place of birth were unremarkable.
This analysis confirms earlier observations of high proportional mortality from diabetes among men employed in the manufacture and repair of clothing in England and Wales, and indicates that the excess extends to most other occupations involving production of, or work with, textiles. Similar but less marked elevation of mortality was also apparent for IHD, although the job groups with the highest PMRs were not the same as for diabetes. PMRs were reduced after adjustment for place of birth, but remained significantly elevated. In contrast, mortality from diabetes and IHD in female textile and fabric workers was not clearly and consistently different from that in all occupations combined.
The consistency of PMRs over time, with relatively tight confidence intervals, especially in analyses for all textile and fabric workers combined, makes it extremely unlikely that this unusual pattern of mortality is attributable to chance. Nor does it seem plausible that PMRs as high as those for diabetes in male textile and fabric workers could be explained by unusually low mortality from other causes.
The explanation previously proposed for the high mortality from diabetes among male garment workers was that many immigrants from the Indian sub-continent worked in these occupations . Our analysis confirmed that an unusually high proportion of deceased male textile and garment workers were born in the Indian sub-continent, whereas no similar concentration was found in deceased female textile and fabric workers. Moreover, Table 3 demonstrates that, as expected, people born in the Indian sub-continent had high mortality from diabetes and IHD, a phenomenon that is likely to reflect the impact of various risk factors including genetic constitution, patterns of nutrition both early and later in life, and levels of physical activity. However, among male textile and garment workers, mortality from both diseases was consistently high within individual place of birth strata, and after standardisation for place of birth, the PMR for diabetes was still clearly elevated (133, 95%CI 110-159). For IHD, it was also high, but at a level (109) that might perhaps be explained by unusually low mortality from other common causes of death (i.e. a difference in the denominators rather than the numerators of proportions).
The persistent high mortality from diabetes after adjustment for place of birth raises the possibility of an unrecognised hazard in the workplace. Various occupational exposures have been linked with an increased risk of diabetes, including arsenic, dioxins and other chlorinated organic compounds, N-nitroso compounds and cutting oils . However, none of these associations is well established, and none of the chemicals is a major exposure across the range of textile and fabric occupations in which mortality from diabetes was elevated. Nor is it apparent why these or any other occupational hazard of diabetes in textile and fabric workers should be specific to men.
Suspicion remains, therefore, that the increased PMR for diabetes, even after adjustment for place of birth, may be a product of uncontrolled residual confounding. It is possible, for example, that male textile and fabric workers include high representation of a subset of Asian-born immigrants with exceptionally high rates of diabetes.
The best way to resolve the continuing uncertainty may be through morbidity surveys in different groups of textile workers, comparing their prevalence of diabetes with that of controls from the same communities who have worked only in other occupations.
Current evidence does not point to a hazard in the workplace requiring preventive action.
We thank the Office for National Statistics for providing us with data. The Health and Safety Executive provided financial support for analytical work carried out by the Health and Safety Laboratory. Clare Harris was supported by the Colt Foundation. Vanessa Cox helped in preparation of data files at the MRC Epidemiology Resource Centre.
Competing Interests: None declared
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