Authors' replyBMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7059.753c (Published 21 September 1996) Cite this as: BMJ 1996;313:753
- S Harding, Senior research analyst,
- R Balarajan, Professor
- Longitudinal Study, Office for National Statistics, London WC2B 6JP
- Institute of Public Health, University of Surrey, Guildford GU2 5YL
EDITOR,—J K Cruikshank raises the important issue of the likely contribution of smoking to the increased mortality from all cancers, and especially lung cancer. Mortality from respiratory disease was also raised in both men (non-significantly) and women. Unfortunately, we do not have data on smoking in the Office for National Statistics' longitudinal study.
We believe that, though testing for significance is central to the analysis, the observation of patterns that are consistent across sex, age, and time is equally important in epidemiological studies. Small numbers are often a major problem, even in studies such as the Office for National Statistics' longitudinal study, which has around 650 000 members in the cohort. With the period of follow up extended from 1971-89 to 1971-92, we are able to test the statement of H M P Fielder and colleagues that “the difference between the second generation Irish women and all women disappears after adjustment for social class.” Table 1 shows that the increased mortality among women is significant at the 5% level after adjustment for social class.
We were careful not to speculate on the genetic component of “Irishness.” This is because we believe that a gradient in mortality across having one or both parents born in the Republic of Ireland represents not only a possible genetic contribution but, importantly, the effect of lifestyle and cultural factors (“ethnic features”) that could persist across generations. We consider variation in lifestyle factors to be an integral part of ethnic analysis and likely to be a major contributor in this case.
While we agree with Fielder and colleagues that health problems of second generation Irish people are not comparable with those of population groups for whom language and culture may cause difficulties in access to health care, this does not rule out the fact that Irish people may have problems different from those of the majority population. This would apply not only to second generation but also to first generation Irish people.1 How can it be wrong to direct time and effort to this group when an opportunity to achieve considerable health gains exists?
We disagree with Fielder and colleagues that if concerted efforts were made to address health problems connected with socioeconomic deprivation in the whole population then the issue of the health of Irish people would be addressed. Though socioeconomic status is important, it cannot explain the excess mortality shown in table 1.