Rurality of communities and incidence of stroke: a confounding effect of weather conditions?

Introduction: An urban-rural gap in stroke incidence or mortality has been reported. However, whether the effect of rurality on stroke is independent of the distribution of conventional individual-level risk factors and other community-level risk factors is inconclusive. Methods: A cohort study was conducted involving 4849 men and 7529 women residing in 12 communities throughout Japan. Baseline data were obtained between April 1992 and July 1995. Follow up was conducted annually to capture first-ever-in-life stroke events. During that period, geographic, demographic and weather information was obtained for each community. Multi-level logistic regression analysis was conducted to evaluate the association between stroke incidence and each geographic/demographic factor adjusted for meteorological parameters (temperature and rainfall), in addition to individual-level risk factors (age, body mass index, smoking, total cholesterol, hypertension, and diabetes). Results: Throughout an average of 10.7 years' follow up, 229 men and 221 women with stroke events were identified. In women, low population (odds ratio [OR] per 1000 persons 0.97; 95% confidence interval 0.94-1.00), low population density (OR per 1/km2 0.85; 0.74-0.97) and high altitude (OR per 100 m 1.18; 1.09-1.28) increased the risk of stroke independently of individual-level risk factors; however, significance was absent for all three associations when further adjusted for weather parameters. Conversely, the association between each meteorological parameter and stroke in women was significant, even after adjustment for each of the three geographic/demographic factors. Similar results were obtained for cerebral infarction. Conclusion: The association between living in rural communities and stroke may be caused by the confounding effect of weather conditions in the communities studied.This study was supported by a Scientific Research Grant from the Ministry of Education, Culture, Sports, Science and Technology, Tokyo, Japan, and grants from the Foundation for the Development of the Community, Tochigi, Japan

Melt-Mixing by Novel Pitched-Tip Kneading Disks in a Co-Rotating Twin-Screw Extruder

Melt-mixing in twin-screw extruders is a key process in the development of polymer composites. Quantifying the mixing performance of kneading elements based on their internal physical processes is a challenging problem. We discuss melt-mixing by novel kneading elements called "pitched-tip kneading disk (ptKD)". The disk-stagger angle and tip angle are the main geometric parameters of the ptKDs. We investigated four typical arrangements of the ptKDs, which are forward and backward disk-staggers combined with forward and backward tips. Numerical simulations under a certain feed rate and screw revolution speed were performed, and the mixing process was investigated using Lagrangian statistics. It was found that the four types had different mixing characteristics, and their mixing processes were explained by the coupling effect of drag flow with the disk staggering and pitched-tip and pressure flows, which are controlled by operational conditions. The use of a pitched-tip effectively to controls the balance of the pressurization and mixing ability