Profound changes in breast cancer incidence may reflect changes into a Westernized lifestyle: A comparative population‐based study in Singapore and Sweden

Abstract

Breast cancer incidence in Sweden has always been approximately twice as high as in Singapore. In recent years, this difference is limited to postmenopausal women. The aim of this study was to explore the reasons behind these differences through the use of age-period-cohort modeling. This population-based study included all breast cancer cases reported to the Swedish and the Singapore cancer registries from 1968 to 1997, with a total of 135,581 Swedish and 10,716 Singaporean women. Poisson regression using ageperiod and age-cohort models was used to determine the effects of age at diagnosis, calendar period and birth cohort. Incidence rate ratios were used to summarize these effects. An age-cohort model provided the best fit to the data in both countries, indicating that changes over lifetime, rather than recent differences in medical surveillance, might account for the observed differences in these 2 populations. The changes over birth cohort were much greater among Singaporean women. The relative effect of age was very similar in the 2 countries. Analyses show that age and cohort effects may explain the differences in trends of female breast cancer incidence between Sweden and Singapore. The larger cohort effect seen in Singaporean women may be attributed to more rapid changes in reproduction and lifestyle patterns than that of Swedish women during the period studied. The incidence of breast cancer in postmenopausal women in Singapore will probably continue to rise in the coming decades to match the current Swedish rates.

Cost effectiveness of mammography screening for Chinese women

“…Moreover, nearly all women with mammographydetected DCIS would undergo major excision and potentially disfiguring (physically and psychologically) operations. 13 It is noteworthy that the age-specific incidence pattern after age 40 years is a much slower rising plateau in Hong Kong and is very similar to that observed in Singapore, 50 with a clear cohort effect in which women who were born after 1945 have progressively higher incidence. In our previous study, 11 we also observed that the average annual increase in age-standardized breast cancer incidence was 1.2% from 1973 to 1999 and was driven largely by a cohort effect of westernization from the generation of the postwar migrants, who were the first generation of girls (and particularly adolescent girls) to experience in large numbers the more westernized lifestyle associated with socioeconomic development.…”

Time trends of cancer incidence in urban Beijing, 1998–2007

“…Recent studies show that, similar to the countries and regions that had rapid socioeconomic growth, western lifestyle, mental stress or anxiety, early age at menarche, late age at menopause, non-breastfeeding and the history of benign breast diseases might be the risk factors for the higher incidence rate of breast cancer in urban Beijing [15][16][17][18] .…”

Epidemiology and the causes of breast cancer

“…It has been suggested that, in some countries, increases in rates have occurred in a pattern characteristic of generations or Ôbirth cohorts,Õ that is, as if the increases occurred very early in life and remained characteristic of the generation throughout life. 26,27 This is clearly not the case in Japan, for, if it were, the inflection in the age curve from increasing to level rates would have occurred in later age-groups ).…”