title: Ambient Temperature and Cerebrovascular Hemodynamics in the Elderly.
abstract: OBJECTIVE
  Some prior studies have linked ambient temperature with risk of cerebrovascular events. If causal, the pathophysiologic mechanisms underlying this putative association remain unknown. Temperature-related changes in cerebral vascular function may play a role, but this hypothesis has not been previously evaluated.
  
  
  METHODS
  We evaluated the association between ambient temperature and cerebral vascular function among 432 participants ≥65 years old from the MOBILIZE Boston Study with data on cerebrovascular blood flow, cerebrovascular resistance, and cerebrovascular reactivity in the middle cerebral artery. We used linear regression models to assess the association of mean ambient temperature in the previous 1 to 28 days with cerebrovascular hemodynamics adjusting for potential confounding factors.
  
  
  RESULTS
  A 10°C increase in the 21-day moving average of ambient temperature was associated with a 10.1% (95% confidence interval [CI], 2.2%, 17.3%) lower blood flow velocity, a 9.0% (95% CI, 0.7%, 18.0%) higher cerebrovascular resistance, and a 15.3% (95%CI, 2.7%, 26.4%) lower cerebral vasoreactivity. Further adjustment for ozone and fine particulate matter (PM2.5) did not materially alter the results. However, we found statistically significant interactions between ambient temperature and PM2.5 such that the association between temperature and blood flow velocity was attenuated at higher levels of PM2.5.
  
  
  CONCLUSIONS
  In this elderly population, we found that ambient temperature was negatively associated with cerebral blood flow velocity and cerebrovascular vasoreactivity and positively associated with cerebrovascular resistance. Changes in vascular function may partly underlie the observed associations between ambient temperature and risk of cerebrovascular events.
authors.affiliation: Department of Epidemiology, Brown University School of Public Health, Providence, RI, United States of America.
authors.forename: Wen-Chi
authors.initials: WC
authors.lastname: Pan
authors.affiliation: Department of Epidemiology, Brown University School of Public Health, Providence, RI, United States of America.
authors.forename: Melissa N
authors.initials: MN
authors.lastname: Eliot
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA, United States of America.
authors.forename: Petros
authors.initials: P
authors.lastname: Koutrakis
authors.affiliation: Department of Biostatistics, Harvard School of Public Health, Boston, MA, United States of America.
authors.forename: Brent A
authors.initials: BA
authors.lastname: Coull
authors.affiliation: Department of Neurology, Brigham and Women's Hospital and Institute for Aging Research, Hebrew SeniorLife, Boston, MA, United States of America.
authors.forename: Farzaneh A
authors.initials: FA
authors.lastname: Sorond
authors.affiliation: Department of Epidemiology, Brown University School of Public Health, Providence, RI, United States of America.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wellenius
mesh_terms: D000368:Aged; D000393:Air Pollutants / Q000032:analysis; D000397:Air Pollution; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002560:Cerebrovascular Circulation; D004781:Environmental Exposure; D005260:Female; D006439:Hemodynamics; D006801:Humans; D016014:Linear Models; D008297:Male; D020768:Middle Cerebral Artery / Q000473:pathology; D052638:Particulate Matter / Q000032:analysis; D011446:Prospective Studies; D012307:Risk Factors; D013696:Temperature
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter