BMC Public Health 2007, 7:230 http://www.biomedcentral.com/1471-2458/7/230 researcher and the translators to ensure that the meaning of the questions did not change. contacts with people from culture of origin [46]. This resulted in the following two components: The total sample consisted of 1556 persons with a Turkish origin, aged 10–30 years. Approximately 13% could not be traced because of incorrect address information. Of the 1354 respondents that could be traced, 768 participated in the study (57 %). Most cases of 'non response' were refusals to participate (32 %) or the persons could not be reached after three attempts (12 %). For the current study we only included participants of 15– 30 years of age, resulting in 236 men and 249 women. We used 15 years as our lower age cut-off point because we expected acculturation to have less effect on physical activity among children below this age [39]. In addition, the greatest decline in physical activity is generally found in adolescence between 13–16 years of age [40,41]. Physical activity during leisure time Physical activity during leisure time was assessed using one component of the Short QUestionnaire to ASsess Health enhancing physical activity (SQUASH) which includes questions about sports and other leisure time activities like walking, cycling, gardening and doing odd jobs during leisure time [42]. This instrument is compara- ble with the International Physical Activity Questionnaire (IPAQ) [43]. Dancing was added to the questionnaire since it is a common activity among Turkish girls and women. Total minutes of activity were calculated by mul- tiplying frequency (days/week) by duration (min/day). Activity scores for separate questions were calculated by multiplying total minutes of activity by the intensity score. All activities were coded according to the Compen- dium of Physical Activities of Ainsworth [44]. The inten- sity score was expressed in MET's (i.e. metabolic equivalent or number of times resting metabolic rate). Subjects were classified as being active during leisure time when they undertook at least 30 minutes (or 60 minutes for people under the age of 18) of moderate activity per session at least one day a week. The main reason for this definition is the fact that more than half of the partici- pants were not participating in any leisure time physical activity. Therefore, we considered the distinction between any activity versus none relevant for this population. For people aged younger than 18 years, the cut-off point for moderate activity was 5 MET or higher and 4 MET or higher for people aged 18 and older [45]. Indicators of acculturation The indicators of acculturation were based on Berry's approach whereby acculturation is considered in terms of orientation towards the majority culture versus culture of origin and social contacts with the host population versus 'Cultural orientation' was measured by 10 items about lan- guage use with family members and friends, use of media, difficulties with reading the Dutch language, shopping preferences and emancipation as an example of Western norms and values [47,48]. The cultural orientation scale was constructed using principal component and reliabil- ity analysis (alpha = 0.64). 'Social contacts with ethnic Dutch' were measured by three questions about contacts with ethnic Dutch people during leisure time (alpha = 0.84). The scores on the items in each scale were summed and a mean substitution was made for cases where one item was missing. To distinguish between the lower and the higher acculturated persons, the upper third was categorized as being high acculturated and the remaining two third as being low acculturated. Using this categorization we had large enough numbers of participants to perform stratified analyses. Contextual barriers Physical environment of the neighbourhood was assessed by a 19-item list containing neighbourhood characteristics on which participants could agree or disagree on a 4-point scale [49]. The variables included availability of side- walks, availability of cycle lanes, neighbourhood aesthet- ics, perceived safety from crime and perceived safety from traffic. People who scored negatively on 8 or more items were categorized as living in a less attractive environment. Occupational physical activity was measured by one ques- tion about how many hours a week people were engaging in physical activity at work such as walking a lot or carry- ing heavy loads. Participants were categorized as being active at work when they participated for at least 30 min- utes a day (5 days a week) in occupational activities with moderate intensity (≥4.0 MET) [44]. Children under 16: Participants were asked if they had chil- dren under the age of 16 living with them. Exercise inhibiting or supportive context: we added one over- all measure of contextual barriers by dividing the partici- pants into people who experienced at least one of the mentioned barriers (exercise inhibiting context) versus people who experienced none of the mentioned barriers (exercise supportive context). Analysis Logistic regression analysis (SPSS 12.0.1 for windows) was used to assess the association between both indicators Page 3 of 9 (page number not for citation purposes)