Association between Neighborhood Supermarket Presence and Glycated Hemoglobin Levels among Patients with Type 2 Diabetes Mellitus

We estimated associations between neighborhood supermarket gain or loss and glycemic control (assessed by glycated hemoglobin (HbA 1c) values) in patients from the Kaiser Permanente Northern California Diabetes Registry (n = 434,806 person-years; 2007-2010). Annual clinical measures were linked to metrics from a geographic information system for each patient's address of longest residence. We estimated the association between change in supermarket presence (gain, loss, or no change) and change in HbA 1c value, adjusting for individual- and area-level attributes and according to baseline glycemic control (near normal, <6.5%; good, 6.5%-7.9%; moderate, 8.0%-8.9%; and poor, ≥9.0%). Supermarket loss was associated with worse HbA 1c trajectories for those with good, moderate, and poor glycemic control at baseline, while supermarket gain was associated with marginally better HbA 1c outcomes only among patients with near normal HbA 1c values at baseline. Patients with the poorest baseline HbA 1c values (≥9.0%) had the worst associated changes in glycemic control following either supermarket loss or gain. Differences were not clinically meaningful relative to no change in supermarket presence. For patients with type 2 diabetes mellitus, gaining neighborhood supermarket presence did not benefit glycemic control in a substantive way. The significance of supermarket changes on health depends on a complex interaction of resident, neighborhood, and store characteristics.