Hadjisavvas et al. BMC Cancer 2010, 10:447 http://www.biomedcentral.com/1471-2407/10/447 risk of breast cancer appeared to be inversely related to the duration of HRT use. Adjusting for number of chil- dren in the multivariable models, did not affect any of the estimates. Indicatively, the odds ratio for family his- tory now becomes 1.62 (95%CI 1.22, 2.16), while the estimates were 0.83 (95% 0.62, 1.09) and 0.67 (95% 0.47, 0.94) in women who reached menarche between the ages of 12-14 and 15 or later respectively. Lastly, infer- ences were also unaffected when breastfeeding was expressed in terms of duration in the multivariable models (instead of the binary classification presented in the table). Discussion The aetiology of breast cancer is still poorly understood and known breast cancer risk factors explain only a small proportion of cases. Epidemiological studies con- ducted in different populations have identified a spec- trum of well established and probable risk factors for breast cancer [15]. These include age, socioeconomic status, reproductive events, breastfeeding, family history and lifestyle among others. However, most epidemiolo- gical breast cancer studies involve subjects living in North America and Western Europe, regions which represent only a fraction of the global population. Therefore there is a need to study breast cancer epide- miology in populations in less-well studied regions of the world, in order to gain a better understanding of breast cancer aetiology [15]. It is noted that this is the first epidemiological study into breast cancer risk factors in the Cypriot population. The main aim of this study was to assess the strength of associations between some recognized risk factors and breast cancer among Cypriot women. We should note that while the factors investigated here (other than BMI) were all self-reported, there is no reason to believe that any recall should be substantially differential, not least due to the standardised interview procedure by which information was collected from both groups of participants. A total of 1109 Cypriot women diagnosed with breast cancer between years 1999-2005 were recruited. It should be noted that the incidence of breast cancer in Cyprus is now around 400 cases per year. The cases in this study represents as many as 50% of the total number of cases diagnosed between 1999-2005. As many as 90% of all breast cancer cases in Cyprus are registered, receive treatment and are followed by the Bank of Cyprus Oncology Centre in Nicosia. This cen- tralized point of access, ensures that the study partici- pants, are to a large extent representative of all cases on the island, in terms of their socio-demographic charac- teristics. It should be noted that the recruitment of cases was based on the list of scheduled appointments Page 7 of 10 during the study period and not on a random selection of all diagnosed cases. The 1177 controls were recruited amongst women who participated in the National breast cancer screening programme with the use of mammography, to a large extent the same population that would give rise to the cases. Since no matching was employed, unavoidable (small) differences in the age distribution between the cases and the controls (mainly due to the under-repre- sentation of younger and older age-groups amongst the mammography screening users) were dealt with by adjusting for age in multivariable analyses. The Cypriot National screening programme for breast cancer in all women aged 50-69 was officially introduced in 2006, after being pilot tested at a small-scale in 2003. Recent data from the Cyprus Ministry of Health suggest that more than half of the women invited respond to the call. Even so this does not imply that the sample of con- trols are representative of the general female population on the island, in terms of the background socio-eco- nomic characteristics and levels of potential risk factors for breast cancer in the general population. In terms of the basic demographic characteristics of the two groups, no major differences were detected in the levels of education or marital status. However, well established risk factors for breast cancer identified in other populations, such as family history of breast can- cer, age at menarche and breastfeeding exhibited the strongest associations with breast cancer risk among Cypriot women [4,5,10]. Unlike Britain and other Eur- opean countries, there are no formal occupation-based socio-economic classification systems in Cyprus. In the absence of such socio-economic indicators or informa- tion on family income, educational status was used as a proxy. Controlling for the possible confounding effect of educational status in multivariable models did not affect inferences about major risk factors of breast cancer. Healthy volunteers who participate in epidemiological studies tend to have a higher educational level, com- pared to the rest of the population [16]. In general, no major differences in the level of education between cases and controls were observed in this study. Never- theless, it is possible that women who attend the screen- ing programme are likely to be more educated, thus masking any such differences. Furthermore, a study of risk factors of breast cancer in Iran has shown that mar- ital status may have an impact on the incidence of breast cancer in Iranian women. It was observed that women who never married were at higher risk for breast cancer [17]. However, marital status by itself may not be a determining factor for modifying breast cancer risk. Since there is a strong interaction between marital sta- tus and parity, the increased breast cancer risk