• Epidemiology
• mortality studies

In their article, Coggon and colleagues1 report on work-related mortality in England and Wales over the period 1979–2000. Occupational mortality studies are one of the oldest approaches in epidemiology, including the decennial reports on patterns of mortality for occupational groups in England and Wales that have been published since the 19th century. These studies have made use of routinely collected data (death certificates), to study cause-specific mortality patterns by occupation and socioeconomic status. Even today, few other study designs, if any, can provide such a wide range of information on the occupational health status of a population, for so little cost.

Nevertheless, occupational mortality studies are currently not held in high regard. This perhaps reflects the low status of descriptive epidemiology- and hypothesis-generating studies in general,2 but there are additional specific methodological concerns regarding occupational mortality studies. In particular, most occupational mortality studies have used census data to produce standardised mortality ratios (SMRs). Using such external denominator data risks the introduction of a numerator-denominator bias, as the occupation registered on the census (usually the self-reported occupation of that person), is not fully comparable with the occupation registered on the death certificate (usually the last held occupation of the deceased as reported by the next of kin). There therefore has been ‘a certain reluctance in accepting mortality excesses registered for specific occupational groups in these studies’.3 Other criticisms of occupational …