title: Socio-economic disparities in the burden of seasonal influenza: the effect of social and material deprivation on rates of influenza infection.
abstract: BACKGROUND
  There is little empirical evidence in support of a relationship between rates of influenza infection and level of material deprivation (i.e., lack of access to goods and services) and social deprivation (i.e. lack of social cohesion and support).
  
  
  METHODS
  Using validated population-level indices of material and social deprivation and medical billing claims for outpatient clinic and emergency department visits for influenza from 1996 to 2006, we assessed the relationship between neighbourhood rates of influenza and neighbourhood levels of deprivation using Bayesian ecological regression models. Then, by pooling data from neighbourhoods in the top decile (i.e., most deprived) and the bottom decile, we compared rates in the most deprived populations to the least deprived populations using age- and sex-standardized rate ratios.
  
  
  RESULTS
  Deprivation scores ranged from one to five with five representing the highest level of deprivation. We found a 21% reduction in rates for every 1 unit increase in social deprivation score (rate ratio [RR] 0.79, 95% Credible Interval [CrI] 0.66, 0.97). There was little evidence of a meaningful linear relationship with material deprivation (RR 1.06, 95% CrI 0.93, 1.24). However, relative to neighbourhoods with deprivation scores in the bottom decile, those in the top decile (i.e., most materially deprived) had substantially higher rates (RR 2.02, 95% Confidence Interval 1.99, 2.05).
  
  
  CONCLUSIONS
  Though it is hypothesized that social and material deprivation increase risk of acute respiratory infection, we found decreasing healthcare utilization rates for influenza with increasing social deprivation. This finding may be explained by the fewer social contacts and, thus, fewer influenza exposure opportunities of the socially deprived. Though there was no evidence of a linear relationship with material deprivation, when comparing the least to the most materially deprived populations, we observed higher rates in the most materially deprived populations.
authors.affiliation: Children's Hospital Informatics Program, Children's Hospital Boston, Boston, Massachusetts, United States of America. katia.charland@mcgill.ca
authors.forename: Katia M
authors.initials: KM
authors.lastname: Charland
authors.forename: John S
authors.initials: JS
authors.lastname: Brownstein
authors.forename: Aman
authors.initials: A
authors.lastname: Verma
authors.forename: Stephanie
authors.initials: S
authors.lastname: Brien
authors.forename: David L
authors.initials: DL
authors.lastname: Buckeridge
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D017281:Cost of Illness; D005260:Female; D054624:Health Status Disparities; D054625:Healthcare Disparities / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000191:economics* / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D011610:Psychosocial Deprivation; D011792:Quebec / Q000453:epidemiology; D012307:Risk Factors; D012621:Seasons; D012923:Social Class; D012959:Socioeconomic Factors; D055815:Young Adult