[Metformin use and risk of ischemic stroke in patients with type 2 diabetes: A cohort study]

OBJECTIVE

To explore the association between the use of metformin and the risk of ischemic stroke in patients with type 2 diabetes.

METHODS

A prospective cohort study was designed from the Fangshan family cohort in Beijing. According to metformin use at baseline, 2 625 patients with type 2 diabetes in Fangshan, Beijing were divided into metformin group or non-metformin group and the incidence of ischemic stroke between the different groups during follow-up was estimated and compared by Cox proportional hazard regression model. The participants with metformin were first compared with all the parti-cipants who did not use metformin, and then were further compared with those who did not use hypoglycemic agents and those who used other hypoglycemic agents.

RESULTS

The patients with type 2 diabetes were with an average age of (59.5±8.7) years, and 41.9% of them were male. The median follow-up time was 4.5 years. A total of 84 patients developed ischemic stroke during follow-up, with a crude incidence of 6.4 (95%CI: 5.0-7.7) per 1 000 person-years. Among all the participants, 1 149 (43.8%) took metformin, 1 476 (56.2%) were metformin non-users, including 593 (22.6%) used other hypoglycemic agents, and 883 (33.6%) did not use any hypoglycemic agents. Compared with metformin non-users, the Hazard ratio (HR) for ischemic stroke in metformin users was 0.58 (95%CI: 0.36-0.93; P = 0.024). Compared with other hypoglycemic agents, HR was 0.48 (95%CI: 0.28-0.84; P < 0.01); Compared with the group without hypoglycemic agents, HR was 0.65 (95%CI: 0.37-1.13; P=0.13). The association between metformin and ischemic stroke was statistically significant in the patients ≥ 60 years old compared with all the metformin non-users and those who used other hypoglycemic agents (HR: 0.48, 95%CI: 0.25-0.92; P < 0.05). Metformin use was associated with a lower incidence of ischemic stroke in the patients with good glycemic control (0.32, 95%CI: 0.13-0.77; P < 0.05). In the patients with poor glycemic control, and the association was not statistically significant (HR: 0.97, 95%CI: 0.53-1.79; P>0.05). There was an interaction between glycemic control and metformin use on incidence of ischemic stroke (P_interaction < 0.05). The results of the sensitivity analysis were consistent with the results in the main analysis.

CONCLUSION

Among patients with type 2 diabetic in rural areas of northern China, metformin use was associated with lower incidence of ischemic stroke, especially in patients older than 60 years. There was an interaction between glycemic control and metformin use in the incidence of ischemic stroke.

[Prevalence of heart failure and its association with smoking behavior in adults from 10 regions of China]

Objective: To describe the prevalence of heart failure in China and to explore the prospective association between smoking behavior and the risk of incident heart failure. Methods: The subjects were from the China Kadoorie Biobank (CKB) and the baseline survey was conducted from June 2004 to July 2008. A total of 487 197 subjects were included in this study, after excluding those with missing BMI information, lost follow-up immediately after baseline investigation, and self-reported coronary heart disease, stroke, or malignant tumor at baseline. This study included data from baseline and follow-up until December 31, 2016. Cox proportional hazards regression models were used to estimate the association between smoking behavior and the risk of heart failure. Results: The median follow-up time was 10.15 years, during which a total of 4 208 new cases of heart failure occurred, with a crude incidence rate of 0.87/1 000 person-years and a cumulative incidence rate of 0.86%. The higher the age at baseline, the higher the incidence of heart failure. The incidence of heart failure in high age group, rural area and male was higher than that in low age group, urban area and female population respectively. Compared with non-smokers, there was no significant difference in the risk of heart failure in occasional smokers (HR=1.05; 95%CI: 0.91-1.22), while former smokers (HR=1.48; 95%CI:1.31-1.67) and current smokers (HR=1.34;95%CI:1.22-1.49) increased risk. Former smokers (HR=1.33;95%CI:1.21-1.46) and current smokers (HR=1.46; 95%CI:1.31-1.64) had higher risk of heart failure than non-smokers or occasional smokers. No dose-response relationship was observed between the number of cigarettes smoked per day and the risk of heart failure in current and former smokers (for trend P=0.347 and 0.066). Compared with non-smokers or occasional smokers, the hazard ratios of <5, 5-, 10- and ≥20 years since quit smoking were 1.61 (95%CI: 1.36-1.92), 1.55 (95%CI: 1.27-1.90), 1.24 (95%CI: 1.02-1.51) and 1.35 (95%CI: 1.08-1.68), respectively (for trend P=0.091). The hazard ratios of quitting smoking due to disease and other reasons were 1.62 (95%CI:1.41-1.86) and 1.23 (95%CI: 1.04-1.45). Healthy smoking behaviors had a significant protective effect on heart failure compared with non-healthy smoking behaviors (HR=0.75, 95%CI:0.69-0.81). Area and family history of coronary heart disease, and the smoking behaviors interacted with the risk of heart failure (for all interactions were P<0.05). Conclusions: The incidence of heart failure in China is higher in males than females, higher in rural areas than in urban areas, and increases with age. Both former smokers and current smokers had a higher risk of heart failure than nonsmokers or occasional smokers, regardless of the frequency, amount, duration, and reason for quitting. Smoking is an important risk factor for heart failure and comprehensive anti-smoking measures should be maintained.

Superior pillared clay catalysts for selective catalytic reduction of nitrogen oxides for power plant emission control

Fe(3+)-, Cr(3+)-, Cu(2+)-, Mn(2+)-, Co(2+)-, and Ni(2+)-exchanged Al2O3-pillared interlayer clay (PILC) or TiO2-PILC catalysts are investigated for the selective catalytic reduction (SCR) of nitric oxide by ammonia in the presence of excess oxygen. Fe(3+)-exchanged pillared clay is found to be the most active. The catalytic activity of Fe-TiO2-PILC could be further improved by the addition of a small amount of cerium ions or cerium oxide. H2O and SO2 increase both the activity and the product selectivity to N2. The maximum activity on the Ce-Fe-TiO2-PILC is more than 3 times as active as that on a vanadium catalyst. Moreover, compared to the V2O5-WO3/TiO2 catalyst, the Fe-TiO2-PILC catalysts show higher N2/N2O product selectivities and substantially lower activities (by approximately 85%) for SO2 oxidation to SO3 under the same reaction conditions. A 100-hr run in the presence of H2O and SO2 for the CeO2/Fe-TiO2-PILC catalyst showed no decrease in activity.

Predictive Sagiv-Stroeve Model for Diffusion through Monolayer and Multilayer Films

A one-parameter model has been derived by A. Sagiv and P. Stroeve for diffusion through crystalline monolayer and multilayer Langmuir-Blodgett films (J. Colloid Interface Sci. 204, 173 (1998)). The model can describe well a number of experimental observations. The parameter that is needed for the model, the activation rate constant (k), is obtained by fitting the experimental data. It is shown in this letter that the parameter can be calculated independently; hence, the model can be predictive. Examples for predictions are given. Copyright 1999 Academic Press.