title: Socioeconomic inequalities in non-communicable diseases prevalence in India: disparities between self-reported diagnoses and standardized measures.
abstract: BACKGROUND
  Whether non-communicable diseases (NCDs) are diseases of poverty or affluence in low-and-middle income countries has been vigorously debated. Most analyses of NCDs have used self-reported data, which is biased by differential access to healthcare services between groups of different socioeconomic status (SES). We sought to compare self-reported diagnoses versus standardised measures of NCD prevalence across SES groups in India.
  
  
  METHODS
  We calculated age-adjusted prevalence rates of common NCDs from the Study on Global Ageing and Adult Health, a nationally representative cross-sectional survey. We compared self-reported diagnoses to standardized measures of disease for five NCDs. We calculated wealth-related and education-related disparities in NCD prevalence by calculating concentration index (C), which ranges from -1 to +1 (concentration of disease among lower and higher SES groups, respectively).
  
  
  RESULTS
  NCD prevalence was higher (range 5.2 to 19.1%) for standardised measures than self-reported diagnoses (range 3.1 to 9.4%). Several NCDs were particularly concentrated among higher SES groups according to self-reported diagnoses (Csrd) but were concentrated either among lower SES groups or showed no strong socioeconomic gradient using standardized measures (Csm): age-standardised wealth-related C: angina Csrd 0.02 vs. Csm -0.17; asthma and lung diseases Csrd -0.05 vs. Csm -0.04 (age-standardised education-related Csrd 0.04 vs. Csm -0.05); vision problems Csrd 0.07 vs. Csm -0.05; depression Csrd 0.07 vs. Csm -0.13. Indicating similar trends of standardized measures detecting more cases among low SES, concentration of hypertension declined among higher SES (Csrd 0.19 vs. Csm 0.03).
  
  
  CONCLUSIONS
  The socio-economic patterning of NCD prevalence differs markedly when assessed by standardized criteria versus self-reported diagnoses. NCDs in India are not necessarily diseases of affluence but also of poverty, indicating likely under-diagnosis and under-reporting of diseases among the poor. Standardized measures should be used, wherever feasible, to estimate the true prevalence of NCDs.
authors.affiliation: South Asia Network for Chronic Diseases, Public Health Foundation of India, New Delhi, India. sukumar.vellakkal@phfi.org
authors.forename: Sukumar
authors.initials: S
authors.lastname: Vellakkal
authors.forename: S V
authors.initials: SV
authors.lastname: Subramanian
authors.forename: Christopher
authors.initials: C
authors.lastname: Millett
authors.forename: Sanjay
authors.initials: S
authors.lastname: Basu
authors.forename: David
authors.initials: D
authors.lastname: Stuckler
authors.forename: Shah
authors.initials: S
authors.lastname: Ebrahim
mesh_terms: D000293:Adolescent; D000328:Adult; D000787:Angina Pectoris / Q000453:epidemiology*; D001249:Asthma / Q000453:epidemiology*; D002908:Chronic Disease / Q000453:epidemiology; D003863:Depression / Q000453:epidemiology*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology*; D007194:India / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012959:Socioeconomic Factors; D014786:Vision Disorders / Q000453:epidemiology*