BMC Public Health 2009, 9:221 http://www.biomedcentral.com/1471-2458/9/221 Area-level crime The area-level crime rates were represented as the mean number of police-reported crimes per 1000 inhabitants per year (year 2003–2005) according to the penal codes presented in Table 2. Demographic characteristics Age (in 2005) was grouped in three categories: 'young' as 20–34 years, 'middle-age' as 35–64 years and 'elderly' as 65–79 years of age. Education was grouped by length of education. The participants were classified into three groups: 'low educated' as 1–9 years in school, 'middle educated' as 10–12 years in school and 'high educated' as more than 12 years in school. Country of birth was catego- rized as 'born in Sweden' or 'elsewhere'. Household civil sta- tus was categorized as 'family household' when living with a spouse or significant other and/or children or 'single household' when living alone. Type of housing was catego- rized as 'small house' or 'flat'. Statistical method A factor analysis was performed to derive simplified dimensions of safety-related concerns from the set of var- iables measuring several aspects of perceived safety. The primary variables included in the analyses were the extent of graffiti, car theft, litter, disturbance by neighbours, dis- rupted sleep, disturbance by tobacco smoking and alcohol consumption, sense of safety during the day, evening and night, and fear of crime. The extraction method was prin- cipal component analysis and an orthogonal rotation was performed with varimax and Kaiser normalization using the option of replacement of missing values with the mean in SPSS [41]. For each dimension of perceived safety identified, the fac- tor scores were computed for each respondent. Due to the skewness of the distribution of the factor scores (p < 0.001) [42], these were dichotomised by the upper quar- tile, for use as input variables in subsequent statistical analyses. A total of 1097 persons with no missing values on risk item and condition variables were included in the subse- quent analyses. Logistic regressions with robust estimates of standard errors were performed to examine associa- tions between derived concepts of safety-related concerns and area- and individual-level variables. Clustering effects within each neighbourhood were taken into account by calculating robust estimates of standard errors in Stata. The multivariate adjusted odds ratios with 95% confi- dence intervals were estimated for total area crime rate (area-level characteristic), having been a victim of crime, area reputation, gender, age, education, country of birth, household civil status and type of housing (small house vs flat) (individual characteristics). A level of 5% was consid- ered to be statistically significant. Ethical aspects The study was approved by the Regional Committee for Research Ethics at Linköping University. Results Non-responder characteristics The response rate varied between areas and was the high- est in area Gamma-house (detached houses), 158/231 (68%), and lowest in area Gamma-flat (blocks of flats), 175/391 (45%). External dropout analysis showed no sta- tistically significant differences in gender among the responders compared to the study population in five of the six areas, but in area Alpha-house more females and fewer males responded than expected. The responders were older than the study population in three areas (Alpha-house, Beta-mix, Beta-flat). The group of 'middle educated' (10–12 years) responders was underrepresented in three areas (Alpha-house, Alpha-flat, Beta-mix) but there was no statistically significant difference in the dis- tribution of country of birth between the responders and the study population (Table 3). Composite dimensions of deficient residential safety Three composite dimensions of residential safety-related concerns were identified in the factor analysis: 'structural indicators of social disorder', 'contact with disorderly behaviour' and 'existential insecurity' (Table 4). Each composite dimension was associated with different sets of modifying items and conditions. Structural indicators of social disorder Area-level crime rates were associated with reporting by the residents of structural indicators of social disorder (OR 1.010, CI 1.007–1.013) (Table 5). Residents who estimated their area reputation as less good were more than twice as likely to report concerns about structural indicators of social disorder (OR 2.86, CI 2.13–3.84). For females, the odds ratio of reporting such concerns was lower (OR 0.78, CI 0.65–0.94). Residents born abroad reported concerns about structural indicators of social dis- order to a lower extent (OR 0.68, CI 0.55–0.84) than res- idents born in Sweden. Living in a flat was associated with concerns in this dimension (OR 1.37, CI 1.01–1.84), but having been a victim of crime, age, and household civil status were not associated (Table 5). Contact with disorderly behaviour The odds ratio for reporting contact with disorderly behaviour was more than five times higher for residents living in flats than for those living in detached houses (OR 5.58, CI 3.06–10.17) (Table 5). Personal experience of crime during the last 12 months increased the likelihood of being concerned about disorderly behaviour in the res- idential area to 1.61 (CI 1.03–2.51). Such concerns were also associated with living in a neighbourhood with esti- mated less favourable reputation (OR 2.91, CI, 2.12– Page 5 of 11 (page number not for citation purposes)