Comparison of information on occupation and lifestyle habits obtained from European man-made vitreous fibre production workers and their relatives

BACKGROUND

Studies of the aetiology of fatal diseases often rely on data obtained from relatives, which can cause loss of precision and introduce bias. We assessed the quality of such information on demographics, occupation, smoking and alcohol habits.

METHODS

We compared contemporary interviews, based on a structured questionnaire, with male workers from the man-made vitreous fibre production industry in four European countries and their relatives. The participation rate was 63% (74 pairs of workers and relatives).

RESULTS

Only minor differences in the ability to answer the questions appeared among workers and relatives, except for specific occupational questions. There was moderate to excellent agreement for demographics, residential and work history (kappa or intraclass correlation range: 0.44-0.98). For smoking habits, beer and wine consumption the agreement was good to excellent (range: 0.59-0.99). In particular, number of different residential areas, jobs, industries, and duration of wine drinking were significantly underreported by the relatives. No general determinant for reduced agreement appeared.

CONCLUSIONS

In general, the quality of information obtained from relatives appeared good. However, information on specific occupational exposures may be improved by supplementing the information from relatives with details obtained from colleagues, occupational hygiene experts or occupation-exposure matrices.

Mortality pattern of German vegetarians after 11 years of follow-up

A cohort of 1,904 vegetarians and persons leading a health-conscious life-style in the Federal Republic of Germany was identified in 1978. After a follow-up of 11 years, mortality from all causes was reduced by one-half compared with the general population [the standardized mortality ratio (SMR) was 0.44 for men, 0.53 for women]. Among the 858 men, 111 deaths were observed, with 255 expected; among the 1,046 women, 114 deaths were observed, with 215 expected. The lowest mortality was found for cardiovascular diseases (SMR = 0.39 for men, 0.46 for women); in particular, for ischemic heart diseases, mortality was reduced to one-third of that expected. Cancer mortality was reduced by one-half in men (SMR = 0.48), but only by one-quarter in women (SMR = 0.74). The deficit in cancer deaths was mainly observed for lung cancer and gastrointestinal cancers in males and for gastrointestinal cancers in females. Deaths from diseases of the respiratory and digestive systems were also reduced by about 50%. An excess of deaths occurred only for anemia. When the strict and the moderate vegetarians were analyzed separately, the strongest differential was found for ischemic heart diseases, which were much less frequent among strict vegetarians for both sexes. Some nondietary factors, such as higher socioeconomic status, virtual absence of smoking, and lower body mass index, may also have contributed to the lower mortality of the study participants.

Natural killer cells, vitamins, and other blood components of vegetarian and omnivorous men

The study population consisted of male vegetarians (aged 28-50 years), who were recruited from the vegetarian cohort being followed by the Department of Epidemiology (German Cancer Research Center, Heidelberg, FRG), and the same number of age- and sex-matched controls from the personnel of the same center. Among the vitamins tested, only the level of carotene was significantly higher in vegetarians; the levels of vitamin A, K, and E were not elevated. Among the other blood parameters tested, only creatinine and glutamine-transferase levels were significantly lower in vegetarians. The natural cytotoxicity of peripheral blood lymphocytes was measured using a chromium-release test. Cytotoxic activity, which is expressed as lytic units, was significantly higher in vegetarians than in their omnivorous controls by a factor of 2. The total number of white blood cells, lymphocytes, and other subpopulations did not differ between vegetarians and nonvegetarians. The enhanced natural cytotoxicity may be one of the factors contributing to the lower cancer risk shown by vegetarians.

Mortality among German vegetarians: first results after five years of follow-up

A prospective study of vegetarians recruited from all regions of the Federal Republic of Germany, including West Berlin, was started in 1978 after a preparatory phase of two years in which the cohort was established. The mortality of the 1,904 study participants was evaluated after a follow-up of five years, comparing observed deaths with expected rates based on the national mortality statistics. Of the 858 men and 1,046 women, 89% had followed their diet for at least five years at study entry, the majority of them as strict vegetarians (1,163). By the end of 1983, only 82 persons had died, whereas 219 deaths were expected. In both sexes, the mortality was lowest from cardiovascular diseases [standardized mortality ratio (SMR) for ischemic heart disease about 20] and from cancer (SMR 58 for men, 54 for women). Deaths from diseases of the respiratory and digestive system were also reduced. For individual cancer sites the observed numbers were extremely small, but the risk of dying from lung cancer was significantly reduced; however, deaths from cancers of the colon and rectum, prostate, and breast were rare or even absent. More deaths than expected were observed from stomach, pancreatic, testicular, and brain cancers. An internal comparison of mortality between strict and moderate vegetarians (741) suggests a higher mortality from all causes and malignant neoplasms among strict vegetarians in both sexes, although not statistically significant, and a lower mortality from circulatory system diseases for males. The possible influence of selection factors (e.g., "healthy participant effect," socioeconomic level, and body weight) on the findings of a decreased mortality is discussed together with the role of diet.

Validity of cause of death statements from relatives

In countries where death certificates are inaccessible for various reasons, cause of death statements made by relatives may gain greater importance. The validity of the cause of death of a deceased family member as stated by relatives compared to the underlying cause as stated on the death certificate has been examined in 310 cases. The sensitivity and the rate of confirmation are highest for neoplasms (both 89.6%). For cardiovascular diseases, the sensitivity (70%) is lower than the rate of confirmation (90%), indicating a certain amount of underreporting. The sensitivity is found to be lowest (50%) for diseases of the respiratory system. Violent deaths, on the other hand, were detected in 93.7%, although confirmed for only 75%. Closer relatives were able to report the cause of death more accurately. The time elapsed since the death of the family member, however, did not affect the recall of the relative. The concrete additional information from relatives, especially for cancer cases, is recommended in the absence of other data sources.