Table 2

Estimated change in prevalence/100 000 per degree of latitude showing the effect of adjustment for year of the study, use of systematic diagnostic criteria and inclusion of possible cases

Prevalence estimates with age-specific data
All crudeCrudeAge-standardised
Slope (95% CI)*Slope (95% CI)*Slope (95% CI)*
Unadjusted1.58 (1.30 to 1.87)0.81 (0.34 to 1.28)1.04 (0.51 to 1.56)
Adjusted for prevalence year3.92 (3.15 to 4.70)2.64 (1.54 to 3.74)2.94 (1.74 to 4.15)
Fully adjusted model3.32 (2.57 to 4.07)2.30 (1.27 to 3.33)2.60 (1.44 to 3.77)
  • * Slope (95% CI)=change in prevalence/100 000 per degree of latitude at the mean global latitude (46.1°) (95% CI).

  • Statistically significant (p<0.001).

  • Adjusted for prevalence year, use of systematic diagnostic criteria and inclusion of possible cases.

  • The model estimates of the residual variance for each age-standardised prevalence model were: 0.7636 (model without covariates), 0.7146 (model with latitude), 0.5839 (model with latitude and prevalence year) and 0.5422 (fully adjusted model).