title: Derivation and validation of BOREAS, a risk score identifying candidates to develop cold-induced hypertension.
abstract: BACKGROUND
  Blood pressure increases in cold periods, but its implications on prevalence of hypertension and on individual progression to hypertension remain unclear. Our aim was to develop a pre-screening test for identifying candidates to suffer hypertension only in cold months among non-hypertensive subjects.
  
  
  METHODS
  We included 95,277 subjects registered on a primary care database from Girona (Catalonia, Spain), with ≥ 3 blood pressure measures recorded between 2003 and 2009 and distributed in both cold (October-March) and warm (April-September) periods. We defined four blood pressure patterns depending on the presence of hypertension through these periods. A Cox model determined the risk to develop vascular events associated with blood pressure patterns. A logistic regression distinguished those nonhypertensive individuals who are more prone to suffer cold-induced hypertension. Validity was assessed on the basis of calibration (using Brier score) and discrimination (using the area under the receiver operating characteristics).
  
  
  RESULTS
  In cold months, the mean systolic blood pressure increased by 3.3 ± 0.1 mmHg and prevalence of hypertension increased by 8.2%. Cold-induced hypertension patients were at higher vascular events risk (Hazard ratio=1.44 [95% Confidence interval 1.15-1.81]), than nonhypertensive individuals. We identified age, diabetes, body mass index and prehypertension as the major contributing factors to cold-induced hypertension onset.
  
  
  CONCLUSIONS
  Hypertension follows a seasonal pattern in some individuals. We recommend screening for hypertension during the cold months, at least in those nonhypertensive individuals identified as cold-induced hypertensive by this assessment tool.
authors.affiliation: Research Unit, Family Medicine, Girona. Jordi Gol Institute for Primary Care Research (IDIAP Jordi Gol), Catalonia, Spain; Girona Biomedical Research Institute (IDIBGI), Dr. Trueta University Hospital, Catalonia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Ponjoan
authors.affiliation: Research Unit, Family Medicine, Girona. Jordi Gol Institute for Primary Care Research (IDIAP Jordi Gol), Catalonia, Spain; Primary Care Services, Girona. Catalan Institute of Health (ICS), Catalonia, Spain; Translab Research Group. Department of Medical Sciences, School of Medicine, University of Girona, Spain.
authors.forename: M M
authors.initials: MM
authors.lastname: García-Gil
authors.affiliation: Research Unit, Family Medicine, Girona. Jordi Gol Institute for Primary Care Research (IDIAP Jordi Gol), Catalonia, Spain; Girona Biomedical Research Institute (IDIBGI), Dr. Trueta University Hospital, Catalonia, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Martí
authors.affiliation: Research Unit, Family Medicine, Girona. Jordi Gol Institute for Primary Care Research (IDIAP Jordi Gol), Catalonia, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Comas-Cufí
authors.affiliation: Research Unit, Family Medicine, Girona. Jordi Gol Institute for Primary Care Research (IDIAP Jordi Gol), Catalonia, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Alves-i-Cabratosa
authors.affiliation: Girona Biomedical Research Institute (IDIBGI), Dr. Trueta University Hospital, Catalonia, Spain; Primary Care Services, Girona. Catalan Institute of Health (ICS), Catalonia, Spain; Translab Research Group. Department of Medical Sciences, School of Medicine, University of Girona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Sala
authors.affiliation: Research on Inflammatory and Cardiovascular Disorders Program (RICAD), Lipids and Cardiovascular Epidemiology Research Group (ULEC) and Cardiovascular, Epidemiology and Genetics Research Group (EGEC), Municipal Institute for Medical Research (IMIM), Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Marrugat
authors.affiliation: Research on Inflammatory and Cardiovascular Disorders Program (RICAD), Lipids and Cardiovascular Epidemiology Research Group (ULEC) and Cardiovascular, Epidemiology and Genetics Research Group (EGEC), Municipal Institute for Medical Research (IMIM), Barcelona, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Elosua
authors.affiliation: Translab Research Group. Department of Medical Sciences, School of Medicine, University of Girona, Spain; Research Unit, Healthcare Institute (IAS), Salt, Girona, Spain.
authors.forename: G Coll
authors.initials: GC
authors.lastname: de Tuero
authors.affiliation: Research on Inflammatory and Cardiovascular Disorders Program (RICAD), Lipids and Cardiovascular Epidemiology Research Group (ULEC) and Cardiovascular, Epidemiology and Genetics Research Group (EGEC), Municipal Institute for Medical Research (IMIM), Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Grau
authors.affiliation: Research Unit, Family Medicine, Girona. Jordi Gol Institute for Primary Care Research (IDIAP Jordi Gol), Catalonia, Spain; Girona Biomedical Research Institute (IDIBGI), Dr. Trueta University Hospital, Catalonia, Spain; Primary Care Services, Girona. Catalan Institute of Health (ICS), Catalonia, Spain; Translab Research Group. Department of Medical Sciences, School of Medicine, University of Girona, Spain. Electronic address: rramos.girona.ics@gencat.cat.
authors.forename: R
authors.initials: R
authors.lastname: Ramos
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D003080:Cold Temperature / Q000009:adverse effects*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology* / Q000209:etiology; D016015:Logistic Models; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D015995:Prevalence; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012621:Seasons; D055815:Young Adult
keywords: Blood pressure; Season; Temperature; Vascular disease; Winter