Oh et al. BMC Public Health 2010, 10:74 http://www.biomedcentral.com/1471-2458/10/74 use background in the language native to each country. Current and former smokers were also asked questions about starting smoking. Our primary outcomes of interest were 1) ever smok- ing and 2) age at smoking initiation. Women who reported smoking “every day”, “some days or occasion- ally”, or “not anymore (>100 cigarettes in life)”, were combined to create a group of “ever smokers”. Partici- pants with a smoking history were asked at what age they first started smoking regularly. Background characteristics with prior associations with smoking initiation were included in the analyses, such as age, education, marital status, and income. Since educational systems differ across countries, we measured education as the age at last year of education. Age at last year of education was categorized into less than 16, 16 to 19, 20 to 25, and over 26 years old. These cate- gories were meant to approximately reflect those who did not finish secondary school, those who finished sec- ondary school, those who went to university, and those who had post-graduate education. Respondents report- ing being divorced and separated were combined into one category for analysis. In order to create comparable categories between countries, information on personal household income was collected relative to the national median household disposable income for 2005-6 for their respective country. For example, the actual ques- tion asked in Ireland was “Given that the median annual household income in Ireland is approximately 43 000 euro, would you say that your household income is well below, below, around, above or well above the median?” The national medians provided to respondents were: 30 000 euro for France (2005; source INSEE), 230 000 krona for Sweden (2006; source Statistiska centralbyran), 32 000 euro for Italy (2006; source Bank of Italy), 110 000 koruna for the Czech Republic (2006; source Czech Statistical Office), 43 000 euro for Ireland (2006; source Central Statistics Office Ireland). Information on friends and family smoking was also collected for the analysis. Those who reported that “more than half” or “most or all” of their friends and family smoked were combined into one category for analyses. Women were also asked if any of their parents, step-parents, or guardians smoked. Using an open-ended question format, ever smokers were asked to list reasons why they started smoking. Answers were recorded as the participant responded and participants could list more than one reason. Analyses All analyses were done with SAS version 9. Chi-squared tests were conducted to test differences between coun- tries. Logistic regression analyses were conducted to determine factors associated with ever smoking and Page 3 of 11 young smoking initiation. Mean age at initiation was compared across country, age, income category, and education. When comparing age cohorts, those who initiated after the age of 24 (~10%) were excluded to remove age-related bias. One-way ANOVA tests were used to test differences in means. Linear regression was conducted to determine if any reasons for smoking initiation were associated with younger age at initiation. Results A total of 5 000 women were interviewed for this study, including 1 000 women from each of the five countries. Demographic characteristics are listed in Table 1. Over 40% of participants (n = 2378) had ever smoked (>100 cigarettes in lifetime). Age ranged from 18 to 95 with approximately 37% of participants over the age of 55 (Table 1). Older age was significantly associated with ever smok- ing (Table 2). In particular, older women in Italy, the Czech Republic and Sweden all showed a significant increasing trend of a smoking history. Education and income measures were not significantly associated with smoking. In the combined analysis and in country-speci- fic analyses for Ireland, Italy and Sweden, divorce or separation was significantly associated with ever smok- ing. In the Czech Republic, being widowed was signifi- cantly associated with not smoking, as compared to married women (Table 2). The widowed Czech women tended to be older, less educated and have a lower income (data not shown). Having increasingly more friends and family who smoke was strongly associated with being more likely to smoke. This trend was significant overall and in each country-specific analysis. The associations were espe- cially strong in the Czech Republic and in Sweden. Par- ent smoking was also significantly associated with ever smoking (Table 2). In all countries, the primary reason women reported for starting to smoke was because their friends smoked (62.3%). The second most frequent reason reported was to make them look ‘more cool’ (25.5%). Only 6.1% of participants reported starting smoking because a family member smoked (Table 3). Some common responses listed under ‘Other’ were curiosity, rebellion, because other people were smoking, or because they had perso- nal problems. Average age at smoking initiation was 18.2 and ranged from 10 to 60 years old. Average age at smoking initia- tion was 17.1 in Sweden, 17.9 in Ireland, 18.1 in France, 18.6 in Italy, and 19.6 in the Czech Republic. Over 80% of women smokers had started smoking by the age of 20. Sweden had the highest percentage of women who started smoking at a very young age with 29.3% starting between 14 and 15 years of age and 12.0% starting