Centre for Primary Care and Public Health, Blizard Institute, Queen Mary University of London, Yvonne Carter Building, 58 Turner Street, London, E1 2AB, UK.
BMC Public Health. 2013 Jan 24;13:70. doi: 10.1186/1471-2458-13-70.
The local retail food environment around schools may act as a potential risk factor for adolescent diet. However, international research utilising cross-sectional designs to investigate associations between retail food outlet proximity to schools and diet provides equivocal support for an effect. In this study we employ longitudinal perspectives in order to answer the following two questions. First, how has the local retail food environment around secondary schools changed over time and second, is this change associated with change in diet of students at these schools?
The locations of retail food outlets and schools in 2001 and 2005 were geo-coded in three London boroughs. Network analysis in a Geographic Information System (GIS) ascertained the number, minimum and median distances to food outlets within 400 m and 800 m of the school location. Outcome measures were 'healthy' and 'unhealthy' diet scores derived from adolescent self-reported data in the Research with East London Adolescents: Community Health Survey (RELACHS). Adjusted associations between distance from school to food retail outlets, counts of outlets near schools and diet scores were assessed using longitudinal (2001-2005 n=757) approaches.
Between 2001 and 2005 the number of takeaways and grocers/convenience stores within 400 m of schools increased, with many more grocers reported within 800 m of schools in 2005 (p< 0.001). Longitudinal analyses showed a decrease of the mean healthy (-1.12, se 0.12) and unhealthy (-0.48, se 0.16) diet scores. There were significant positive relationships between the distances travelled to grocers and healthy diet scores though effects were very small (0.003, 95%CI 0.001 - 0.006). Significant negative relationships between proximity to takeaways and unhealthy diet scores also resulted in small parameter estimates.
The results provide some evidence that the local food environment around secondary schools may influence adolescent diet, though effects were small. Further research on adolescents' food purchasing habits with larger samples in varied geographic regions is required to identify robust relationships between proximity and diet, as small numbers, because of confounding, may dilute effect food environment effects. Data on individual foods purchased in all shop formats may clarify the frequent, overly simple classification of grocers as 'healthy'.
学校周边的本地零售食品环境可能是青少年饮食的潜在风险因素。然而，利用横断面设计研究零售食品店与学校之间的接近程度与饮食之间的关系的国际研究结果并不支持这种关系。在这项研究中，我们采用了纵向的观点来回答以下两个问题。第一，中学周边的本地零售食品环境随时间发生了怎样的变化？第二，这种变化是否与这些学校学生饮食的变化有关？
在伦敦的三个行政区，对零售食品店和学校的位置进行了地理编码。地理信息系统（GIS）中的网络分析确定了学校位置 400 米和 800 米范围内食品店的数量、最小和中位数距离。通过青少年自我报告的数据，在东伦敦青少年研究：社区健康调查（RELACHS）中得出了“健康”和“不健康”饮食得分。采用纵向（2001-2005 年 n=757）方法，对学校到食品零售商店的距离、学校附近商店的数量与饮食得分之间的调整后关联进行了评估。
在 2001 年至 2005 年间，学校附近的外卖店和杂货店/便利店的数量有所增加，而 2005 年学校附近的杂货店数量更多（p<0.001）。纵向分析显示，健康饮食得分（-1.12，se 0.12）和不健康饮食得分（-0.48，se 0.16）均呈下降趋势。前往杂货店的距离与健康饮食得分呈显著正相关，尽管效果非常小（0.003，95%CI 0.001-0.006）。外卖店的接近程度与不健康饮食得分呈显著负相关，且参数估计也很小。
研究结果提供了一些证据，表明中学周边的本地食品环境可能会影响青少年的饮食，但效果很小。需要在不同地理区域的更大样本中进一步研究青少年的食品购买习惯，以确定接近程度与饮食之间的稳健关系，因为由于混杂因素，小样本可能会削弱食品环境的影响。在所有商店形式中购买的个体食品的数据可能会澄清杂货店经常被过于简单地归类为“健康”的问题。
