This study showed how diabetes knowledge plays a key role on diabetes outcomes through self-care behaviors. Remarkably, our study found that, among all the self-care behaviors evaluated, physical activity mediated the association between diabetes knowledge and glycemic control in a low-income population of T2D patients from a large urban area. Both SES and level of education were directly associated with diabetes knowledge, but education showed a stronger impact. Additionally, we found a decreased risk for developing microvascular diabetes-related complications (particularly with distal diabetic neuropathy), with a higher self-care score (particularly with physical activity). To the best of our knowledge, this is the first deep exploration of determinants of health in population with T2D living in a large populated area in Mexico City.
Some previous studies in T2D have determined the mediation of behavioral determinants on the effectiveness of lifestyle interventions in changing behavior and body weight. Texeira et al. found that motivation, self-efficacy, and self-regulation skills were reported as mediators of weight change and physical activity behavior . Den Braver et al. also reported that SLIMMER (SLIM iMplementation Experience Region Noord- en Oost-Gelderland) intervention on fasting insulin and body weight was mediated by changes in dietary and physical activity behavior . Mediation models identify and explain the process that underlies an observed relationship between an independent variable (diabetes knowledge) and a dependent variable (glycemic control) via the inclusion of a third hypothetical variable, known as a mediator variable (i.e., self-care behaviors. To our knowledge, no previous study has determined the potential mediation of self-care behaviors in population from Mexico City, which is particularly susceptible to abnormal cardiometabolism and the worst prognosis [30,31]. For mediation analysis, we used one of the two available approaches: the Sobel test  and bootstrapping . Although the Sobel test has been widely used since 1982, bootstrapping has been strongly recommended in recent years. Hence, we chose to bootstrap our mediation analysis . Using this approach, we determined that physical activity mediated the association between diabetes knowledge and glycemic control in this population setting. This finding coincides with those reported by den Braver et al. , and allows us to focus our non-pharmacologic interventions of this self-care behavior. As the American Association of Diabetes has insisted, physical activity is critical for blood glucose management and overall health in individuals with diabetes , and we ask on its importance in LMICs.
Our population showed some significant differences related to sex-effects. Notably, we found that diabetes knowledge scores were higher in males; however, the education level was higher in women than in men. Also, a higher frequency of neuropathy was observed in women. Sex differences in the impact of T2D on CVD outcomes across the life span have been previously identified [42, 43]. For example, T2D confers 25–50% greater excess risk of incident cardiovascular disease in women compared with men. Obesity trends in women may, in part, explain the observed sex difference in T2D in midlife. In fact, we observed a higher and significant body mass index in females. A deep analysis of sex-dependent differences and the relevance of the observed outcomes are guaranteed.
The present study is in line with previous studies about the benefit of self-care behaviors, particularly physical activity, and provides additional information on the causal path. This study also shows the relevance of diabetes knowledge and self-care behavior in T2D patients. The lack of health-related knowledge and poor performance of diabetes self-care habits could partially explain the heavier diabetes burden in populations with social lag indicators. Previously, diabetes was associated with worse prognoses in Mexico than in high-income countries [47, 48] which made this research obligatory.
Our results showed that self-care behaviors were linked to microvascular damage in any form, with deeper reductions in Hazard Ratios for physical activity and blood sugar testing. Previous studies have also found similar results, both cross-sectionally as longitudinally [49, 50]. However, our study was collected based on self-report data at the time of the interview, and cross-sectionally analyzed. Therefore, because of the nature of the analysis, our results cannot suggest that self-care behavior will derive in reductions in microvascular complications. The effect of interventions and improvements in self-care behavior in T2D patients on long-term microvascular complications in LMICs to establish causality is guaranteed. We also observed some unexplained associations (e.g., global diet and retinopathy), that we could not explain and that could be due to potential confounders not included in our statistical models.
An important finding was the elucidation of socioeconomic factors on diabetes knowledge. Both factors evaluated, SES and education level, played a major role in diabetes knowledge, particularly education. This finding suggests there is a causative role of socioeconomic factors in the epidemic of complications of diabetes mellitus in underdeveloped countries. Poverty influences the development of type 2 diabetes and complications . Education and socioeconomic levels are associated with the activation of self-care management in chronic diseases . These two social determinants could partially influence the poor performance in self-care habits, through the potential contribution and mediating effect of poor diabetes knowledge, which indicates a link between social determinants of health and diabetes self-management. Moreover, socioeconomic status was directly associated with glucose testing, which identifies the restriction T2D patients and low SES have to execute this behavior. These findings reiterate why health care professionals need to consider their patients’ socioeconomic status when implementing diabetes self-care management and education programs.
One strength of this study is that it included a validated tool for diabetes knowledge (SKILLD), which was designed for vulnerable populations . We observed that most patients scored low on this scale, even though T2D patients with long-term diabetes diagnosis were enrolled, which indicates the need for increasing diabetes education in healthcare programs. The study participants were beneficiaries of Seguro Popular (now INSABI) in Mexico City, which attends to the largest number of primary care outpatients in Mexico. Therefore, our results were obtained from real-world data among a representative population from a low-income subset of patients from one of the largest urban areas in the world, which is home to more than 20 million people in 1,450 km2.
Although our results are novel and potentially useful in the context of diabetes mellitus treatment in low-income countries, our study has several limitations. First, this is a cross-sectional epidemiological study, so we are not able to conclude causality. However, as any other epidemiological study, it is a hypothesis generator, and examines the relevance of education on diabetes knowledge to improve glycemic control. Second, the sample size may seem small in comparison with other diabetes studies. However, our study included a large number of participating health centers in an unprecedented manner. Third, although this study was conducted in Mexico City, a megalopolis, our findings may not be representative of other urban areas across the world. Nevertheless, the study highlights the need to consider social determinants of health and diabetes knowledge across populations that surely share similarities with our sample. Fourth, the SKILLD scale does not have a widespread use among studies that measure diabetes knowledge. Moreover, from our perspective, the traditional tools used for this purpose are difficult to understand for populations with educational lag; hence we decided to administer SKILLD, which has been tested and validated in populations similar to ours. Fifth, despite adjusting for potential confounding factors in our analysis, we did not assess for other factors that may influence glycemic control and self-care behaviors, such as pharmacological treatments, mental disorders, barriers to self-care, etc. Adverse diabetes outcomes are complex and multicausal and involve biological, individual, and social factors. In this work, we try to reinforce the relevance of some of them; we recognize the difficulty of including all the factors involved in a study of this nature.
We also recognize that our study did not evaluate the frequency of smoking in the participants. However, this analysis is part of an interventional program in which the educational component includes strict recommendations to stop smoking and to avoid second-hand smoking to all participants, even though this factor is not present (Silva-Tinoco R. et al., 2020. Int J Equity Health, In press). Future studies about the role of smoking in LMICs are guaranteed. As the inclusion to the study was not randomized and our study was not controlled due to ethical concerns, our results might be affected by selection bias. Only those participants who accepted were included in the program, and they usually lived in areas close to the clinic (i.e., mobility in Mexico City tend to be very complicated on daily basis, and people usually spend hours to move from home to workplaces). However, characteristics of the population shown in Table 1 suggested representativity of the population living at the center of the country in terms of SES, education, diet, and body mass index . The success of the program will allow us to include and evaluate a higher number of participants to determine the generalizability of our results to LMICs. Finally, we recognize that usage of self-reported data may be less reliable because of the potential lack of accuracy of responses, as well as potential intentional and unintentional reporting bias. However, some studies have found that the self-report responses may be 100% in agreement with the direct observations held, suggesting that self-report methodologies can confidently be used in instances where observation may not be feasible. Therefore, our results have to be analyzed in the context of these potential biases for self-reported data.