Inequities in access to exercise facilities and relationship with diabetes burden from an equity perspective in Madrid, Spain

Laburpena

Introduction: Physical activity, specifically exercise, exerts influence on the incidence and prevalence of major health problems, such as obesity, diabetes, and cardiovascular diseases. Among urban built environment resources, the availability of exercise facilities is important for supporting physical activity engagement; however inequitable distribution of exercise facilities exists throughout many cities. The empirical evidence for the associations between the neighbourhood exercise facility environment and health outcomes, especially Type 2 Diabetes Mellitus (T2DM), are weak and has received relatively little attention in public health research. Objectives: This thesis examines the relationship between exercise facility availability, T2DM burden, and area-level socioeconomic status (SES) in in Madrid, Spain through three aims, presented as separate studies. The aims are to: (1) investigate the relationship between area-level socioeconomic status (SES) and accessibility to, and availability of, exercise facilities; (2) study the association between the availability of exercise facilities and the likelihood of obesity and T2DM in the adult population; and (3) examine the relationships between exercise facility availability and incidence of T2DM and its complications. Methods: All exercise facilities in Madrid were identified and classified them into four types: public, private, low-cost, and sessional facilities. Facilities were geocoded using Google Maps and accessibility was operationalised as the street network distance to the nearest exercise facility from each of the 125,427 residential building entrances in Madrid. Exercise facility availability was defined as the count of exercise facilities in a 1000 m street network buffer around each portal. Area-level SES was measured using a composite index based on seven sociodemographic indicators. Health outcome data were obtained from electronic medical records (EMRs) from more than 90% of Madrid residents aged 40-75 years, using data from 2017 for the cross-sectional studies (n=1,270,512) and 2015-2018 (n=1,412,759) for the longitudinal study. Health outcomes studied were obesity, T2DM, and macrovascular (cardiac ischemia and stroke) and microvascular (chronic kidney disease, retinopathy, and peripheral vascular disease) complications of T2DM. For the first study, I carried out a multilevel linear regression and a zero-inflated Poisson regression analysis to assess the association between arealevel SES and exercise facility accessibility and availability in Madrid. For the second study, I used Poisson regression with standard errors clustered at census tract level to assess prevalence ratios (PR) of exercise facility availability (tertiles) with obesity and T2DM. Interactions by area-level SES and sex were also examined. For the third empirical study, I carried out Poisson regression models using robust standard errors clustered at the census tract level to estimate the relative risk (RR) for the association between exercise facilities and each health outcome. Analyses of interactions by area-level SES and sex were undertaken to identify potential effect modification. Results: The first study showed that Madrid residents living in more disadvantaged areas had the shortest mean street network distance to the closest exercise facility, especially for accessing public and low-cost exercise facilities. Meanwhile those living in less disadvantaged areas had higher availability of exercise facilities, especially for private and sessional exercise facilities, compared with those more disadvantaged. The second study showed people living in areas with lower availability of exercise facilities had a higher prevalence of obesity and T2DM compared with those who had a higher availability of exercise facilities. Stratified analysis found an effect modification by arealevel SES, with stronger associations for residents living in low-SES areas, and strongest for women living in low SES neighbourhoods. The third study found that residents living in areas with lower exercise facility availability presented with higher risk of T2DM and macrovascular and microvascular T2DM complications compared with those living in areas with higher availability of exercise facilities. Analysis showed stronger associations for those living in low SES areas with the lowest tertile of exercise facility availability and incidence of T2DM and its microvascular complications compared with those residents from high SES areas. Conclusions: This thesis draws two main conclusions. First, exercise facility accessibility and availability are related to T2DM burden, not only for T2DM itself, but also for its main risk factor (obesity) and macrovascular and microvascular T2DM complications. Second, this set of studies have exposed how socioeconomic inequities play a role in these relationships, by conditioning harmful effects for residents from low SES areas in Madrid. This research generated new knowledge that can help shape exercise-based interventions to reduce health inequities, including increasing availability of exercise facilities in more disadvantaged areas alongside ensuring that the facilities are affordable and gender-appropriate.