ABSTRACT

Evidence for the association between vitamin D and risk of recurrent stroke remains sparse and limited. We aimed to assess the relationship between serum circulating 25-hydroxyvitamin D (25(OH)D) level and risk of recurrent stroke in patients with a stroke history, and to identify the optimal 25(OH)D level in relation to lowest recurrent stroke risk. Data from the nationwide prospective United Kingdom Biobank were used for analyses. Primary outcome was time to first stroke recurrence requiring a hospital visit during follow-up. We used Cox proportional hazards regression model with restricted cubic splines to explore 25(OH)D level in relation to recurrent stroke. The dose-response relationship between 25(OH)D and recurrent stroke risk was also estimated, taking the level of 10 nmol/L as reference. A total of 6824 participants (mean age: 60.6 years, 40.8% females) with a baseline stroke were included for analyses. There were 388 (5.7%) recurrent stroke events documented during a mean follow-up of 7.6 years. Using Cox proportional hazards regression model with restricted cubic splines, a quasi J-shaped relationship between 25(OH)D and risk of recurrent stroke was found, where the lowest recurrent stroke risk lay at the 25(OH)D level of approximate 60 nmol/L. When compared with 10 nmol/L, a 25(OH)D level of 60 nmol/L was related with a 48% reduction in the recurrent stroke risk (hazard ratio = 0.52, 95% confidence interval: 0.33–0.83). Based on data from a large-scale prospective cohort, we found a quasi J-shaped relationship between 25(OH)D and risk of recurrent stroke in patients with a stroke history. Given a lack of exploring the cause–effect relationship in this observational study, more high-quality evidence is needed to further clarify the vitamin D status in relation to recurrent stroke risk.

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Background: Lack of representativeness in Black, Indigenous, and People of Colour (BIPOC) enrollment could compromise the generalizability of study results and health equity. This study aimed to examine trends in BIPOC groups enrollment in diabetes randomized controlled trials (RCTs) and to explore the association between trial factors and high-enrollment of BIPOC groups. Methods:We systematically searched the literature on large diabetes RCTs with a sample size of ≥ 400 participants published between 2000 and 2020. We assessed temporal trends in enrollment of racial and ethnic groups in the included trials. Logistic and linear regression analyses were used to explore the relationship between trial factors and the high-enrollment defined by median enrollment rate.Results: A total of 405 RCTs were included for analyses. The median enrollment rate of BIPOC groups was 24.0%, with 6.4% for the Black group, 11.2% for Hispanic, 8.5% for Asian, and 3.0% for other BIPOC groups respectively. Over the past 20 years, the BIPOC enrollment showed an increased trend in the diabetes RCTs, ranging from 20.1 to 28.4% (P for trend = 0.041). A significant trend towards increased enrollment for Asian group was observed. We found that weekly or daily intervention frequency (OR = 0.48, 95% CI: 0.26, 0.91) and duration of intervention > 6.5 month (OR = 0.59, 95% CI: 0.37, 0.95) were significantly related to decreased odds of high-enrollment, while type 2 diabetes (OR = 1.44, 95% CI: 1.04, 1.99) was associated with high-enrollment of BIPOC groups. Conclusions:The enrollment of BIPOC was found to increase in large diabetes RCTs over the past two decades; some trial factors may be significantly associated with BIPOC enrollment. These findings may highlight the importance of enrollment of BIPOC groups and provide insights into the design and implementation of future clinical trials in diabetes.