Completeness of follow up in a cohort study of mortality using the United Kingdom National Health Service Central Registers and records held by the Department of Social Security

Audit of ascertainment of deaths to children born in Cumbria, UK, 1950-89 through the NHS central register

STUDY OBJECTIVE

To evaluate the completeness of notification of deaths by the National Health Service Central Register (NHSCR) for England and Wales.

DESIGN

Deaths for a birth cohort were ascertained through scanning the relevant volumes of NHSCR. Attempts were made to confirm these deaths and additional deaths were ascertained through searching local records. Logistic regression was used to investigate how the probability of a death being missed by NHSCR varied with the year of birth, age at death, sex, and social class.

SETTING

Deaths up to the end of 1989 in the CA postal area among 264,046 children born between 1950 and 1989 to mothers living in Cumbria.

RESULTS

NHSCR originally ascertained 4139 deaths; local searches confirmed 3338 (81%) of these and found an additional 342. Most deaths missed by the NHSCR were neonatal deaths in the 1950s and 1960s. In the 1950s, 31% of children who died in the neonatal period either were not entered on NHSCR or, if they were entered, there was no record of their death. For children born from 1970 onwards, ascertainment of deaths through NHSCR was over 99% complete.

CONCLUSIONS

The NHSCR was started in 1948 for the administration of records of National Health Service patients. It seems that many babies who died soon after birth were not therefore recorded. In parallel with the increasing use of NHSCR for epidemiological purposes, there has been a substantial and continuing improvement in its clerical procedures since the mid 1960's.

Cancer mortality among local authority pest control officers in England and Wales

OBJECTIVE

To examine cancer mortality by tumour site among local authority pest control officers.

METHODS

Prospective mortality study, and follow up to the end of 1994, of 1485 male pest control officers aged between 17 and 69 and employed in 296 local authorities in England and Wales for at least six months between January 1980 and April 1984. Observed numbers of deaths were compared with those expected on the basis of the rates for relevant calendar year, cause, sex, and age specific groups for England and Wales.

RESULTS

200 deaths occurred during the follow up period of which 65 were certified as due to malignant neoplasms. No tumour type showed significantly more deaths than expected. Total all cause, lung cancer, and respiratory disease mortality were significantly lower than expected.

CONCLUSIONS

15 year follow up of a group of men handling a wide range of pesticides did not show any significant risk of cancer. This may be partially explained by the healthy worker effect and also the limited power of the study to detect significant increases in the less common tumours. Further long term follow up of this cohort will continue. Chemical control of pests that can cause human disease and can contaminate food and water has been, and will continue to be, a major public health measure. It is important to ensure that the health of those applying pesticides is not at excess risk. Negative results are important.

Incompleteness of oral cancer registration in south-east England, 1971-87

Our objective was to examine the accuracy of reporting oral cancer cases to the cancer registry system. We examined a series of 583 patients with oral malignancies treated at several institutions and reported by our laboratory during 1971-87. Using patient details and pathology diagnosis, we traced the entries for these patients in the Thames Cancer Registry (TCR). Of the 583 patients identified 351 were eligible for entry in TCR. Of these, 255 were traced in the Registry and 96 were not (27%). The data, when separated for the period 1971-80 and post-1980, showed that for the earlier period under-reporting was 21% and for the later period 36%: Underascertainment was particularly marked in the mid-1980s while regional registration in the North Thames Regions was being discontinued and taken over by TCR. The major factors contributing to under-reporting are thought to be the fact that many specialised dental units and oral pathology laboratories may fail to be included in the cancer registration process and possible inconsistencies in death-initiated registrations related to this site. Similar levels of under-reporting were observed in another regional registry (South Western), suggesting that this may be a national problem. If this is the case, national incidence rates for mouth cancer may have been underestimated by about 25% during this period. This contrasts with over 90% completeness of registration for cancers as a whole.

Mortality in the British printing industry: a historical cohort study of trade union members in Manchester

A historical cohort study of the printing industry was established after an anecdotal report of a cluster of cases of bladder cancer in a newspaper factory in Manchester. The cohort comprised some 9500 men who were members of one or other of two trade unions (the NGA and NATSOPA) in the Manchester area between 1949 and 1963. During the follow up period (1949-83) 3482 deaths occurred among men born in 1890 or later; follow up was 97% complete. The results of the study do not support the hypothesis of an occupational risk of bladder cancer in the printing industry. The NGA have a standardised mortality ratio (SMR) of 63 (95% confidence interval (95% CI) 31-113) and NATSOPA an SMR of 113 (95% CI 67-178) based on 11 and 18 deaths from bladder cancer, respectively. Men involved in newspaper letterpress printing have a high mortality from lung cancer (SMR = 179, 95% CI 144-218) that is consistent with the findings of previous studies. Increased mortality from cancer of the buccal cavity and pharynx was found for NATSOPA workers in the newspaper industry; editorial workers had an SMR of 1053 (95% CI 128-3803) and clerical workers had an SMR of 638 (95% CI 132-1864). This is consistent with a review of published studies, which strongly suggest that workers in the printing industry have an increased risk of mortality from cancers of the buccal cavity and pharynx. Socioeconomic differences in union composition, rather than occupational factors, may account for the lower mortality in the NGA compared with NATSOPA. The NGA, a craft union, had an all causes SMR of 92 (95% CI 88-97), whereas NATSOPA covered a broader span of occupations and skill levels, and had an all causes SMR of 112 (95% CI 106-117); the NATSOPA and NGA all causes rate ratio was 1.21 (95% CI 1.13-1,29).

Further follow up of mortality in a United Kingdom oil refinery cohort

The results of an extension of follow up (1976 to 1989) of a cohort of workers employed for at least one year between 1 January 1950 and 31 December 1975 at eight oil refineries in Britain are reported. Over 99% of the workers were successfully traced to determine their vital status at 31 December 1989. The mortality observed was compared with that expected from the death rates of all the male population of England and Wales and Scotland. The mortality from all causes of death for the total study population was lower than that of the comparison population, and reduced mortality was also found for many of the major non-malignant causes of death. Raised mortality patterns were found for diseases of the arteries, in particular aortic aneurysm, and accidental fire and explosion, for the total study population, and across several refineries and other subgroups. Mortality from all neoplasms was lower than expected overall, largely due to a deficit of deaths from malignant neoplasm of the lung. Raised mortality from all neoplasms was found for labourers and in particular for malignant neoplasms of the oesophagus, stomach, and lung, although the mortality was also high for all men in this social class in the national population. Regional variations may have accounted for some of the high mortality. There were other raised mortality patterns in malignant neoplasms of the intestine, rectum, larynx, and prostate but these tended to be isolated and not consistent across refineries and other subgroups. As in the earlier follow up there was raised mortality from melanoma in several job groups.

Completeness of cancer and death follow-up obtained through the National Health Service Central Register for England and Wales

For the last 20 years the National Health Service Central Register (NHSCR) has been used as the principal source of follow-up for mortality, and often for cancer incidence, in many cohort and clinical follow-up studies in England and Wales. Completeness of notification of childhood cancer registrations and deaths from the NHSCR was investigated by comparison between cancers and deaths notified to the Childhood Cancer Research Group (CCRG) from this source and notifications received directly from regional cancer registries and the national death registry. Six thousand, seven hundred and seventy-six (91.8%) of 7,379 cancers incident 1971-84, and 588 (95.8%) of 614 deaths occurring 1953-88, were successfully notified. Failures in cancer notification occurred mainly between the regional cancer registries and the National Cancer Register (3.3%), and between the National Cancer Register and the NHSCR (3.0%). An additional 1.9% of cancer notifications failed between the NHSCR and the CCRG. Incompleteness of registration of childhood cancers by regional cancer registries was estimated to be 4.7%. A total of 12.5% of incident childhood cancers were not notified by NHSCR. Incompleteness of notification may be greater for adults, for whom registration and record linkage may be more difficult. Failures in death notifications occurred mostly because deaths entered on the NHSCR were not notified to the CCRG (3.3%). This incompleteness of notification needs to be taken into account in the interpretation of published studies and in the analysis of studies using NHSCR flagging. It also implies similar incompleteness in published national cancer survival data, which use the same system of flagging. Nevertheless it is a notable achievement that NHSCR has successfully monitored such a high proportion of a population of 50 million people, by entirely clerical procedures, for 40 years.