title: Nonlinear association between pulse wave velocity and cognitive function: a population-based study.
abstract: BACKGROUND
  Arterial stiffness has been hypothesized to contribute to cognitive decline. However, previous studies have reported inconsistent results. The aim of this cross-sectional study was to investigate the association between carotid-femoral pulse wave velocity (cfPWV), a marker of arterial stiffness, and cognitive function.
  
  
  METHODS
  The study population comprised 2637 individuals from the population-based Malmö Diet and Cancer Study (mean age 72.1 years, 60.8% women). During the follow-up examinations between 2007 and 2012, cfPWV and results on the a quick test of cognitive speed (AQT) and Mini Mental State Examination (MMSE) cognitive tests were measured.
  
  
  RESULTS
  After adjustments for demographics and traditional cardiovascular risk factors, a linear association was found between cfPWV and AQT (B = 0.37; P = 0.039). On the basis of hypothesis that individuals with high cfPWV values have worse cognitive function than can be inferred from a linear association, cfPWV was dichotomized at the 90th percentile (the binary variable denoted cfPWV >13.8). When cfPWV >13.8 was added to the model, the linear association between continuous cfPWV and AQT disappeared (B = -0.08; P = 0.72), but cfPWV >13.8 was highly significant (B = 4.81; P = 0.004). In the adjusted model with MMSE as outcome variable, cfPWV >13.8 also reached a statistically significant effect.
  
  
  CONCLUSIONS
  Arterial stiffness was inversely associated with cognitive function in a nonlinear fashion, with individuals in the top decentile of cfPWV explaining the association. Results from linear regressions should thus be interpreted with caution because, even when statistical significance is reached, they can be explained by pronounced nonlinearity.
authors.affiliation: aClinical Memory Research Unit, Department of Clinical Sciences, Lund University bDivision of Geriatric Medicine, Department of Health Sciences cDepartment of Clinical Sciences, Lund University, Skåne University Hospital, Malmö, Sweden.
authors.forename: Erik D
authors.initials: ED
authors.lastname: Nilsson
authors.forename: Sölve
authors.initials: S
authors.lastname: Elmståhl
authors.forename: Lennart
authors.initials: L
authors.lastname: Minthon
authors.forename: Peter M
authors.initials: PM
authors.lastname: Nilsson
authors.forename: Mats
authors.initials: M
authors.lastname: Pihlsgård
authors.forename: Eva
authors.initials: E
authors.lastname: Tufvesson
authors.forename: Katarina
authors.initials: K
authors.lastname: Nägga
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002318:Cardiovascular Diseases / Q000503:physiopathology; D003071:Cognition; D003072:Cognition Disorders / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D063177:Pulse Wave Analysis; D012307:Risk Factors; D059289:Vascular Stiffness