Abstract
Time-related trends in the incidence of non-Hodgkin's lymphoma (NHL) in Denmark were analysed for the period 1943-89. A total of 13 822 patients (7565 men and 6257 women) were included in the study. In men, world-standardised incidence rates per 100 000 population increased from 2.5 in 1943-47 to 9.3 in 1988-89. In women, a similar increase was seen, i.e. from 1.9 in 1943-47 to 6.5 per 100 000 population in 1988-89. For all birth cohorts, the male-to-female incidence ratio was highest among young subjects and fell significantly after the age of 29 years. Trends in age-specific incidence were analysed separately for two periods, i.e. 1943-77 and 1978-89, reflecting an early, pre-AIDS period and a later period possibly influenced by AIDS. In both periods, the incidence of NHL increased in all age groups. However, in recent years a noticeable increase in incidence averaging 8% annually was observed in men and women aged 40-49 years. A number of factors including changes in the perception of NHL and in the diagnostic methods available are considered insufficient to explain the observed increase. The remarkable and parallel time trends observed in young men and women in recent years indicate that factors other than AIDS must be considered.
Highlights
An increase in the incidence of non-Hodgkin's lymphoma (NHL) has been reported worldwide in recent years (Hakulinen et al, 1986; Martinsson et al, 1992; Cartwright, 1992; Zheng et al, 1992; Devesa and Fears, 1992; Carli et al, 1994)
For the purpose of the present study, we identified all cases of NHL registered under ICD-7 codes 200 and 202 for the period 1943-89
Summary estimates of the incidence rates in 5 year calendar intervals were calculated by direct standardisation to the age distribution of the world standard population (Breslow and Day, 1980)
Summary
An increase in the incidence of non-Hodgkin's lymphoma (NHL) has been reported worldwide in recent years (Hakulinen et al, 1986; Martinsson et al, 1992; Cartwright, 1992; Zheng et al, 1992; Devesa and Fears, 1992; Carli et al, 1994). Most reports have described annual increases of 25%, some suggesting higher rates of increase in men than in women (Martinsson et al, 1992; Devesa and Fears, 1992). Identification of the point in time when this widespread trend started could yield important information as to possible causes of NHL. The vast majority of previous reports, have been restricted to the most recent decades, and little is known about the temporal trends before the 1960s
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