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This study relates to 1803 newly diagnosed cases of Hodgkin's Disease (HD) registered between 1984 and 1988 by a specialist leukaemia-lymphoma registry covering approximately half of England and Wales. In addition to registration data the analyses use routine census data. Rye classification is available for the majority of cases with only 7% being unclassified. The data confirm that the young adult peak in HD occurrence is attributable to the nodular sclerosing subtype (NS), and there is some evidence that NS has a different geographical distribution by county to the other Rye subtypes. Because of possible geographical biases in the classification, subsequent spatial analyses are disaggregated by age at diagnosis with particular emphasis being placed on the two age groups 0-34 and 50-79 years. For these, trends of risk by areal socioeconomic status are in opposite directions and the effects of urban-rural status while in the same direction also differ significantly. Allowance for these does not, however, explain the significant difference between the county distributions of the two groups. Patterns of spatial clustering are quite distinct with evidence for local spatial aggregation amongst younger cases.

BACKGROUND As part of a nested case-control study of benign proliferative breast disease (BPBD) conducted within the cohort of women participating in the Alberta breast screening programme, an analysis of all women who had a benign breast biopsy between 1990 and 1995 was undertaken to identify the epidemiological risk factors for BPBD. METHODS The breast biopsies of all eligible women were re-reviewed by a panel of four pathologists using Page's classification for benign breast disease. Cases were 165 women whose biopsies, upon review, showed benign breast tissue changes ranging from sclerosing adenosis to atypical ductal hyperplasia. Controls were 217 women whose biopsies showed no evidence of any proliferative or neoplastic changes. In-person interviews were conducted with all study subjects. RESULTS Women with >/=25% fibroglandular breast tissue density, as compared to women with

Background Various methods of analysis have been used to study age-period-cohort models. The main aim of this paper is to illustrate and compare three such methods. Those of Clayton and Schifflers, Robertson and Boyle, and De Carli and La Vecchia. The main differences between these methods lie in their approach to distinguish between linear-period and linear-cohort effects. Clayton and Schifflers do not attempt to solve this identification problem, whereas Robertson and Boyle, and De Carli and La Vecchia attempt to tackle this question. Methods In order to study the assumptions and problems of these methods, we analysed data from 2678 subjects aged 30-84 in Yorkshire, UK, who were diagnosed with non-Hodgkin's lymphoma (NHL) during the period 1978-1991. Loglinear Poisson models were used to examine the effects of age, period and cohort. Results All three methods of analysis agree that, after stratification for sex and county, the age-standardized rate has been increasing at about 5% per year. The Robertson-Boyle method differed from the Clayton-Schifflers method in showing a significant non-linear cohort effect, and a significant county-cohort interaction. The method of De Carli-La Vecchia agreed more closely with Clayton-Schifflers than with Robertson-Boyle. Conclusions The linear increase in incidence would lead to a doubling of the number of cases within 15 years. There is controversy over whether the identification problem can be solved and should be solved. Many authors would not rely on the results of the methods of Robertson and Boyle, or De Carli and La Vacchia.