Changes in some of the demographic indicators and simultaneous increase in the incidence rate of breast cancer in recent decades in Slovenia

The data concerning the changes in some of the demographic indicators and simultaneous increase in the incidence rate of BC in Slovenia were collected and downloaded from open access electronic databases of the National Institute of Public Health of the Republic of Slovenia (National Institute of Public Health of the Republic of Slovenia, 2011), Statistical Office of the Republic of Slovenia (Statistical Office of the Republic of Slovenia, 2011), Slora-Slovenia and Cancer (Slora, 2011) of the Cancer Registry of Republic of Slovenia and from some of the similar sources (Cancer Registry of Republic of Slovenia, 2010; Curado et al (Eds.), 2009; Ilic et al., 2008). In this report the data in the figures refer only to the period from 1961 to 2006 since the data from periods earlier than 1961 are subject to limited availability. The data were processed and presented with the use of Excel 97 for Windows software package.

As already mentioned above, BC is the most common type of cancer and most common cause of death from cancer in Slovenia (Cancer Registry of Republic of Slovenia, 2010; Slora 2011). The incidence rate of BC has been increasing constantly in the last five decades (Figure 1). In a large part of this period, from 1961 to 2006, a simultaneous decrease had been observed in the number of live births annually, in the number of live births per 1,000 population and in total fertility rate (Ilic et al, 2008; Slora, 2011; Statistical Office of the Republic of Slovenia, 2011). The number of live births decreased from 31,828 to 18,932 in the period from 1961 to 2006 (Figure 2), the number of live births per 1,000 population decreased from 18.1 to 9.4 (Figure 3), and total fertility rate decreased from 2.26 to 1.31 in the same period (Figure 4). Conversely, for at least a part of this period, from late-seventies and early-eighties onward, the age of mother at first birth and the age of mother at birth in total both increased (Figure 5) (Ilic et al., 2008; Slora, 2011; Statistical Office of the Republic of Slovenia, 2011). The age of mother at first birth increased from 24.7 years in 1961 to 28 years in 2006, the lowest age of mother at first birth in this period was 22.7 years, observed in 1976, and the age of mother at birth in total increased from 27.7 years in 1961 to 29.7 years in 2006, the lowest age of mother at birth in total in this period was 25.3 years, observed in 1979, 1980 and in 1984 (Figure 5). (Ilic et al., 2008; Statistical Office of the Republic of Slovenia, 2011). Finally, the mean age at death of women increased from 59.8 years in 1954 to 78.1 years in 2006 (Figure 6) (Ilic et al., 2008; Slora, 2011; Statistical Office of the Republic of Slovenia, 2011).

Fig. 1. Breast cancer crude incidence rate (blue line; definition: crude incidence rate is the number of new cases of disease or the number of deceased from the disease, calculated per 100,000 of population-persons, living in observed population in the middle of the time interval, usually one year (Slora, 2011; Statistical Office of the Republic of Slovenia, 2011)) in the period from 1961 to 2006 in Slovenia

Fig. 1. Breast cancer crude incidence rate (blue line; definition: crude incidence rate is the number of new cases of disease or the number of deceased from the disease, calculated per 100,000 of population-persons, living in observed population in the middle of the time interval, usually one year (Slora, 2011; Statistical Office of the Republic of Slovenia, 2011)) in the period from 1961 to 2006 in Slovenia

Considering the changes in some of the aforementioned demographic factors and the corresponding increase in the incidence rate of BC in Slovenia, it is easy to imagine that these changes represent an increase in the risk of BC in women in the period from 1961 to 2006 in this country. Some additional data about changes in population in Slovenia in the recent decades in the following text may corroborate this notion.

As already suggested, the population of both sexes had aged quite rapidly in Slovenia. In 2006 the mean age of the population overall was 40.7 years; 39 years of men and 42.3 years of women. In the period between 1986 and 2006, the population of Slovenia has on average grown older by 5.6 years, by the end of this period men were on average older by 5.7 years and women by 5.6 years. The mean age of men grew the most between 1997 and 1998, and of women between 2001 and 2002 (Ilic et al., 2008). In 2006 the proportion of young population aged 0-14 years was 14% and the proportion of population aged 65 years or more was 15.7%. In the twenty years from 1986 to 2006 the number of individuals in population aged 0-14 years decreased by more than a third (34.8%) and the number of individuals in population aged 65 years or more increased by more than a half (59%) (Ilic et al, 2008). In just ten years, in the period from 1996 to 2006, the number of women in reproductive age (15-49 years) in Slovenia decreased from 518,335 in 1996 to 476,853 in 2006 (Ilic et al, 2008). In 1954 slightly over a third of children were first-born and almost 20% of mothers had at least four children, while in the last three decades of the period from 1954 to 2006 approximately half of all births were first order births (49.6% in 2006), more than one third of births were second order births (35.8% in 2006), slightly more than 10% were third order births (10.9% in 2006) and only about 3% of births were fourth order births or higher (3.7% in 2006) (Ilic et al., 2008).

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Fig. 2. Number of live births (red line; definition: number of live born children in the calendar year) in the period from 1961 to 2006 in Slovenia

In addition, it was also possible to retrieve some further data, for the period from 1954 to 1961, for the age of mother at first birth and the age of mother at birth in total, both risk factors for BC. Altogether, the age of mother at first birth rose from 24.8 years in the year 1954 to 28.0 years in the year 2006. The age of mother at birth in total rose from 28.4 years in 1954 to 29.7 years in 2006 (Ilic et al, 2008). Postponement of birth of the first child is typical for women of many European Union countries, especially in the lowest-low fertility countries. In some of these countries the trends in postponing of births is so intense that annual increase in the mean age is 0.2 years, with extremely fast postponement occurring in Slovenia, Hungary and the Czech Republic. In the United Kingdom, the mean age of women that gave birth to their children for the first time reached 30 years in 2006 (Ilic et al, 2008).

On the whole, increased risk of BC is associated with female gender, advancing age and age during menstrual life, hormonal factors (early menarche and late menopause), nulliparity and age of over 30 years at first birth, obesity and estrogen therapy after the menopause, harmful drinking of alcohol and history of benign proliferative lesions in the breast (Armstrong & Nguyen, 1999; Bryant, 2004; Cancer Registry of Republic of Slovenia, 2010; Curado et al (Eds.), 2009; Henderson et al, 1996; International Agency for Research in Cancer, 2008; Soerjomataram et al, 2008). Risk of BC is also increased in women with one or more first-degree relatives with BC (Henderson et al, 1996), and with inherited mutations of any one of major genes, like BRCA1, BRCA2 and several others (Armstrong & Nguyen, 1999; International Agency for Research in Cancer, 2008).

Fig. 3. Number of live births per 1,000 population (red line; definition: ratio between the number of live born children in the calendar year and the same mid-year population, multiplied by 1,000 (Ilic et al., 2008)) in the period from 1961 to 2006 in Slovenia
Fig. 4. Total fertility rate (red line; definition: the average number of live born children per one woman in reproductive age (15-49 years) in the calendar year (Ilic et al., 2008)) in the period from 1961 to 2006 in Slovenia

It may be of particular interest that the number of women diagnosed with BC in the year 2008 in Slovenia is slightly lower than in the year 2007, when the incidence rate of BC reached 112.9 cases per 100,000 and when BC was diagnosed in 1,156 women (Cancer Registry of Republic of Slovenia, 2010; Slora, 2011). However, the incidence rates of BC are still notably lower in Slovenia than in the United States of America and in a number of other developed European Union countries. It remains to be seen if this small decrease in the incidence rate of BC in Slovenia represents the same type of trend as observed in the United States of America, where the incidence rates of BC decreased by approximately two percent annually in the period from 1999 to 2005 (Centers for Disease Control and Prevention, 2007; Kerlikowske et al, 2007). Later analysis showed that the incidence rate for BC stabilized in the period from 2003 to 2007, following a sharp decrease between 2002 and 2003 observed in women aged 50 years or more (DeSantis et al, 2011a, 2011b), that was associated with the decrease in the use of postmenopausal hormonal replacement therapy (DeSantis et al, 2011b; Kohler et al. 2011; Ravdin et al, 2007).

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Fig. 5. Mean age mother at first birth (dark red line) and mean age of mother at birth-total (light red line) in the period from 1961 to 2006 in Slovenia

All these data to point to changes in the quantity and quality of the work performed at present by midwives employed in the thirteen maternity wards and maternity hospitals, and elsewhere in Slovenia (National Institute of Public Health of the Republic of Slovenia, 2011). The possible role of midwives in the early detection and prevention of BC in the future should thus be carefully appraised and evaluated.

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