In this study of diverse urban residents, several perceived safety and police-recorded crime measures were associated with transport and leisure walking, but not with non-walking leisure activity. This may be because some of these sport activities are not engaged in outdoors or within the neighborhood. Alternatively, non-walking leisure activities may be less affected by crime and perceived safety. A comprehensive review of studies  concluded that there was insufficient evidence to determine that safety was associated with physical activity. However, many of these reviewed studies had limited measures of safety and often did not explore both perceived and more objective measures of safety. Since the review, several other studies explored perceived measures of safety (for example [21–26]), others explored police-recorded measures of crime (for example [27, 28]), and three studies explored both perceived and objective safety measures [5, 11, 12]. Most of these more recent studies identified associations of safety or crime with physical activity. Similar to our findings, prior studies found low agreement between perceived and objective measures of safety and crime, regardless of how measured, suggesting that the two measures might be assessing different dimensions of one’s physical environment [5, 9, 11, 12].
Our results on transportation walking are consistent with other work documenting that fear of crime affects use of public transportation . For example, studies have documented fear of crime at transit stations and several researchers [30, 31] argue that fear of crime has an impact on travel decisions by individuals. Analysis of the environs of rapid transit stations in Chicago indicated that areas near a transit station in relatively low crime neighborhoods had higher levels of crime than the surrounding area [32, 33]. We demonstrated that crime was associated with a lower probability of transport walking. Thus, strategies to reduce crime in neighborhoods and around public transportation areas may not only increase the use of public transportation, with consequent environmental benefits, but may also increase physical activity through the promotion of walking.
Our results confirm some aspects of the frameworks proposed by others [1, 2], in that both perceived safety and police-recorded measures of crime appear to be independently associated with physical activity, in particular walking. While police-recorded crime in the neighborhood was only weakly correlated with perceived safety, similar to other studies [5, 9, 11, 12, 28, 34, 35], it also was an independent predictor of transport walking or exercise. Furthermore, the strongest associations between safety and transport walking and exercise were observed among persons living in the safest neighborhoods, according to the combined measures of safety that utilized both reporting a safe neighborhood and police-recorded measures of crime as compared to those living in areas that both were reported as being unsafe and fell in the highest category for police-recorded crimes. To explore these combined associations of both perceived and police-recorded crime, we created variables that grouped the safest and unsafest groups together, with a third category of all other participants. With more data, an alternative exploration could be made into participants that over-reported their safety (participant perceives neighborhood is safe but police reports indicate it is unsafe) and under-reported their safety (participant perceives neighborhood is unsafe but police reports indicate it is safe).
We found that among women perception of safety was strongly associated with transport walking or leisure in a variety of models, while the associations were weaker or null among men. This is in line with a US study of adults living in low-income housing that found that a perception of feeling unsafe at night was associated with fewer pedometer recorded steps/day among women but not men . Another study of 75–76 year old Norwegian women and men found that violence in the neighborhood was associated with physical activity among men, while perceived safety was associated with physical activity among women . We did not observe interactions of perceived safety with education. This is in agreement with a US study of adults age 50 years and older . We also did not identify interactions of perceived safety with race/ethnicity. Other studies are needed with larger sample sizes and diverse populations to further explore these associations.
Our study has several important limitations. First, other confounders may exist that we did not account for in the adjusted models. For example, we were unable to control for self-selection to the neighborhood (i.e., if a participant lives in a neighborhood because it is safer to walk), nor did we assess for their actual victimization experience. Second, in this exploratory study we have tested many associations, but did not adjust for multiple testing. Therefore, significance should be interpreted with caution, and replication of results is needed. It should be noted that the findings were attenuated when adjusting for the neighborhood correlation, indicating the influence the correlation had on the findings. Third, while the study assessed self-reported physical activity comprehensively, a supplemental objective measure of physical activity was not assessed. Moveover, the prevalence of physical activity was likely over-reported because of the number of activities queried upon. Due to self-report bias and the skewness of the measures, physical activity was categorized, which resulted in some loss of precision. Fourth, we also have limited information on where people engaged in physical activity, although transport walking most likely occurs near the home or workplace. The baseline survey indicated that 68.3% of these Chicago MESA participants reported that the place they use most often for exercise was 1 mile or less from their home. Additionally, 90.8% reported exercising within a 20-minute walk or 1 mile from their home.
Fifth, the detailed crime data was summarized to the census block group level so there may be some misattribution. Although the census block group represents a small area, especially in this dense location, it still may not adequately represent the neighborhood of the participant. Data were not available at the time the analyses were conducted to examine crime measures for other spatial contexts, such as distance around home or participant-defined boundaries. Little theory or prior data exists on which to base the relevant definition of neighborhood for these analyses . Moreover, the reported crimes are likely to be under-reported. There may also be some mismatch in time between the general recall of neighborhood safety as compared to the 2-year period of police-recorded crimes. We chose a 2-year period to reflect more stable trends in the area, but other windows of time may be more appropriate. Sixth, for the self-reported safety measures, both items lacked sufficient sample at the extreme unsafe range (not at all safe and violence a serious problem), such that these categories were collapsed. Seventh, this study was limited by its cross-sectional design. Finally, generalizability may be limited as this study focused on one Midwestern urban city in the US among 45 to 84 year old adults. Moreover, we were unable to explore the possibility of selection bias with our sample.
As noted earlier, the literature indicates that the relationship between physical activity and safety may be differential by gender, socioeconomic status, and race/ethnicity . In addition, these relationships may be modified by psychosocial or environmental factors. Further in-depth qualitative and quantitative studies with sufficient statistical power and diversity should explore these complex relationships. Moreover, the inclusion of other age groups would be worthwhile, as this study focused on 45 to 84 year old adults.
While difficult to explore with epidemiologic studies, an exploration of the microenvironments that provide proximate cues regarding safety is also needed to understand how these features influence the choice to walk or be active in these settings [37, 38]. Examples of features that might influence use of a space include prospect (is the view blocked or open), refuge (is there a hiding place), escape (open or blocked exit), naturalness (natural or developed elements), upkeep (maintenance), openness (visual scope or vista), number of people, type of land use (business, park, etc.), and complexity (amount of different noticeable elements) .
While we were able to explore aspects of the frameworks proposed by others [1, 2], greater specificity of measurement and comprehensiveness continue to be needed. Further, safety may mediate the relationship between these environmental features and physical activity. As proposed by others , the relationship between perceived safety and physical activity may be bidirectional, with perceived safety influencing physical activity and also physical activity behavior influencing perceived safety. Longitudinal studies would enhance this work by helping with the temporality of the associations. Interventions are also needed to target groups with the highest perception of crime and in the areas with the highest objective measures of crime to potentially have the greatest population impact not only on physical activity but on other measures (e.g., general health, stress, neighborhood collective efficacy).