The study presented showed that the use of SGLT2 inhibitors in patients with T2D and CKD decreased the risk of NOS. The results of the study also indicated a decreased risk of incident stroke in patients with T2D and CKD was greater in female and younger (< 50 years) patients. This study also demonstrated that type of SGLT2 inhibitor subgroup analysis for NOS showed consistent results.
Previous studies on the association between SGLT2 inhibitors and NOS in patients with T2D and CKD have been inconsistent [11–14]. A recent study found a trend toward lower rates of stroke in patients with the lowest estimated glomerular filtration rate (less than 60 mL/min/1.73 m2) (HR: 0.77; 95% CI 0.55–1.08) who used SGLT2 inhibitors [15], but no study has yet shown a lower risk of total stroke in patients with T2D and CKD. However, a meta-analysis did indicate that the effects of SGLT2 inhibitors on total stroke varied depending on baseline estimated glomerular filtration rate, with the greatest protection seen in patients with the lowest estimated glomerular filtration rate (less than 45 mL/min/1.73 m2) [16]. Our study showed that there was evidence that SGLT2 inhibitors affected total stroke in patients with T2D and CKD.
The mechanisms behind the protective effects of SGLT2 inhibitors on cardiovascular disease are not fully understood but may involve reductions in glucose, systolic blood pressure, and arteriosclerosis, as well as protective effects on the heart and kidneys [9, 10, 17–19]. In vitro data suggest that SGLT2 inhibitors improve glucose-induced vascular dysfunction by reducing inflammation and oxidative stress, reversing pro-inflammatory phenotypes, and glucotoxicity in diabetic rats [20].
It is possible that previous studies did not see similar functional effects of SGLT2 inhibitors. However, this current study indicates that canagliflozin, dapagliflozin, and empagliflozin have similar effects in decreasing the number of stroke events. The exact mechanisms behind the beneficial effect of SGLT2 inhibitors on stroke risk are not clear but may involve a reduction in incident atrial fibrillation and atrial flutter. Previous studies and meta-analyses have shown that SGLT2 inhibitors can reduce the risk of incident atrial fibrillation and atrial flutter in patients with T2D and therefore decrease the risk of stroke [16, 21].
Previous epidemiologic studies reveal a clear age-by-sex interaction in stroke incidence [22–24]. A retrospective cohort study from the US health insurance database between 2001 and 2014 including 5.8 million participants found that women had a higher stroke incidence below 44 years of age [24]. Moreover, there are also an epidemiological study show that the trend in decreasing age at diagnosis for stroke and its risk factors appears to be more pronounced among women [25]. The results of this study indicated a decreased risk of incident stroke in patients with T2D and CKD was greater in female and younger (< 50 years) patients. Therefore, earlier identification of stroke risk factors and use SGLT2 inhibitor in younger women with T2D and CKD may provide opportunity to preventive stroke.
The strengths of our study included its population-based nature and large sample size. Our findings were tested using propensity score matching to control for potential confounders, which made our hypothesis feasible. Our study is the first one to provide an association between the use of SGLT2 inhibitor on total stroke risk in patients with T2D and CKD. We found a statistically significant decrease in the risk of NOS among patients who are SGLT2 inhibitor users.
There are several limitations of our investigation that must be noted. First, the study outcome was defined as stroke and comorbidities diagnosis recorded by physicians and were completely dependent on the ICD-10 CM codes; therefore, it is unclear that how our findings can be generalized to patients in different areas of the world. Second, the present study has a retrospective design and the information on several unmeasured confounders, including body mass index, smoking, alcohol intake, and labortory data such as glomerular filtration rate and urinary albumin-to-creatinine ratio, is not available in the National Health Insurance Research Database. However, considering the magnitude and significance of the observed effects, it is unlikely that these limitations compromised the results. Third, the process of stroke in patients who developed NOS in this study would have started many years before the diagnoses, and NOS may have coexisted with the process of T2D and CKD for which SGLT2 inhibitors were used. Thus, the cause-and-effect relationships between NOS and SGLT2 inhibitors cannot be determined in this study. Hence, further a prospective randomized control trial is needed for more detail.