title: Effects of temperature and relative humidity on DNA methylation.
abstract: BACKGROUND
  Previous studies have found relationships between DNA methylation and various environmental contaminant exposures. Associations with weather have not been examined. Because temperature and humidity are related to mortality even on non-extreme days, we hypothesized that temperature and relative humidity may affect methylation.
  
  
  METHODS
  We repeatedly measured methylation on long interspersed nuclear elements (LINE-1), Alu, and 9 candidate genes in blood samples from 777 elderly men participating in the Normative Aging Study (1999-2009). We assessed whether ambient temperature and relative humidity are related to methylation on LINE-1 and Alu, as well as on genes controlling coagulation, inflammation, cortisol, DNA repair, and metabolic pathway. We examined intermediate-term associations of temperature, relative humidity, and their interaction with methylation, using distributed lag models.
  
  
  RESULTS
  Temperature or relative humidity levels were associated with methylation on tissue factor (F3), intercellular adhesion molecule 1 (ICAM-1), toll-like receptor 2 (TRL-2), carnitine O-acetyltransferase (CRAT), interferon gamma (IFN-γ), inducible nitric oxide synthase (iNOS), and glucocorticoid receptor, LINE-1, and Alu. For instance, a 5°C increase in 3-week average temperature in ICAM-1 methylation was associated with a 9% increase (95% confidence interval: 3% to 15%), whereas a 10% increase in 3-week average relative humidity was associated with a 5% decrease (-8% to -1%). The relative humidity association with ICAM-1 methylation was stronger on hot days than mild days.
  
  
  CONCLUSIONS
  DNA methylation in blood cells may reflect biological effects of temperature and relative humidity. Temperature and relative humidity may also interact to produce stronger effects.
authors.affiliation: From the aDepartment of Environmental Health, Harvard School of Public Health, Boston, MA; bDepartment of Biostatistics, Harvard School of Public Health, Boston, MA; cDepartment of Medical Statistics, London School of Hygiene and Tropical Medicine, London, United Kingdom; dInstitute of Epidemiology, Helmholtz Zentrum München German Research Center for Environmental Health, Neuherberg, Germany; eCenter of Molecular and Genetic Epidemiology, University of Milan, Milan, Italy; and fVA Boston Healthcare System and the Department of Medicine, Boston University School of Medicine, Boston, MA.
authors.forename: Marie-Abele
authors.initials: MA
authors.lastname: Bind
authors.forename: Antonella
authors.initials: A
authors.lastname: Zanobetti
authors.forename: Antonio
authors.initials: A
authors.lastname: Gasparrini
authors.forename: Annette
authors.initials: A
authors.lastname: Peters
authors.forename: Brent
authors.initials: B
authors.lastname: Coull
authors.forename: Andrea
authors.initials: A
authors.lastname: Baccarelli
authors.forename: Letizia
authors.initials: L
authors.lastname: Tarantini
authors.forename: Petros
authors.initials: P
authors.lastname: Koutrakis
authors.forename: Pantel
authors.initials: P
authors.lastname: Vokonas
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D020087:Alu Elements / Q000235:genetics; D019175:DNA Methylation; D004260:DNA Repair; D006801:Humans; D006813:Humidity / Q000009:adverse effects*; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics; D008297:Male; D008875:Middle Aged; D013696:Temperature