title: The changing relationship between rainfall and children's physical activity in spring and summer: a longitudinal study.
abstract: BACKGROUND
  Weather conditions, along with day length, are proposed as the main drivers of the seasonal patterns in children's physical activity (PA), but little is known about how they affect children at different ages. This study examines the relationship between rainfall and PA in a longitudinal cohort of initially 9-10 year-old children in Norfolk, UK.
  
  
  METHODS
  Participants were 283 children from the SPEEDY study who wore accelerometers ≤7 days on three occasions in the summer of 2007, 2008 and 2011 at ages 9-10, 10-11, and 13-14y. Daily weather data were obtained for two local weather stations. Relationships between rainfall and PA (moderate-to-vigorous-PA (MVPA; ≥2000) vigorous PA (VPA; ≥4000), counts per minute (cpm)) and sedentary time were assessed in multiple-membership multilevel models. PA was assessed over the whole day, and over parts of the school day; commute time (8 am-9 am and 3 pm-4 pm), lunchtime (12noon-2 pm), and after school (4 pm-9 pm).
  
  
  RESULTS
  At ages 9-10 and 10-11y, PA declined with increasing rainfall, with an average of 14.0 (SE 2.9) and 11.4 (3.0) minutes less MVPA on the wettest days (≥1.7 mm rain) compared to dry days respectively. There was no significant trend in MVPA across rainfall categories at age 13-14 years. Between ages 9-10 and 13-14, MVPA decline was largest on dry days (-15.2 (2.7) minutes). These patterns were also apparent during school lunchtime and after school, however they were not seen during school commute times. Similar patterns were seen for other PA intensities.
  
  
  CONCLUSIONS
  Increased rainfall is associated with significant decreases in PA among primary school children, but not secondary school children. PA declines most steeply between the ages of 9-10 and 13-14 on dry days. Interventions to increase activity on wet days may be most relevant at primary schools. Our results also highlight the importance of habitualising behavior to make children more resilient both to bad weather, and potentially age-related decline in activity.
authors.affiliation: Norwich Medical School & UKCRC Centre for Diet and Activity Research, University of East Anglia, Norwich, UK. flo.harrison@uea.ac.uk.
authors.forename: Flo
authors.initials: F
authors.lastname: Harrison
authors.affiliation: MRC Epidemiology Unit & UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, Institute of Metabolic Science, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. esther.vansluijs@mrc-epid.cam.ac.uk.
authors.forename: Esther M F
authors.initials: EM
authors.lastname: van Sluijs
authors.affiliation: MRC Epidemiology Unit & UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, Institute of Metabolic Science, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. klc29@medschl.cam.ac.uk.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Corder
authors.affiliation: MRC Epidemiology Unit & UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, Institute of Metabolic Science, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. ulf.ekelund@nih.no.|Department of Sports Medicine, Norwegian School of Sports Sciences, Ullevål Stadion, Oslo, Norway. ulf.ekelund@nih.no.
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.affiliation: Norwich Medical School & UKCRC Centre for Diet and Activity Research, University of East Anglia, Norwich, UK. a.p.jones@uea.ac.uk.
authors.forename: Andy
authors.initials: A
authors.lastname: Jones
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D002652:Child Behavior; D015444:Exercise; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009043:Motor Activity; D055361:Multilevel Analysis; D011891:Rain; D012574:Schools; D012621:Seasons; D057185:Sedentary Behavior; D006113:United Kingdom