Role of smoking in regional variation in mortality in Poland

We assess the effect of smoking on regional disparities in mortality in Poland and its contribution to the change in regional disparities during the last two decades.

We used population-level mortality data from the population registry for 379 Nomenclature of Territorial Units for Statistics (NUTS)-4 Polish regions for 1991-93 and 2008-10.

The importance of smoking was assessed by smoking-attributable mortality (SAM) derived using a simplified indirect Peto-Lopez method. Regional differences in age-standardized all-cause, smoking- and non-smoking-attributable mortality (NSAM) rates at ages 35 years and over were mapped, and spatial clustering (Moran's I) and coefficients of variation (CV) were estimated. The contribution of SAM to variation in all-cause mortality was assessed by variance decomposition and compared over time.

In 2008-10, all-cause and SAM rates were characterized by a similar pattern of spatial clustering (Moran's I > 0.44, P < 0.0001). For NSAM, a more random pattern with less regional clustering showed (Moran's I = 0.34, P < 0.0001). The contribution of smoking to regional variation was substantial [54%, 95% confidence interval (CI) = 44.9, 62.5 among men; 24.9%, 95% CI = 20.9, 29.1 among women], and compared with 1991-93, 27.5 percentage points lower for men and 6.3 percentage points higher for women. Smoking contributed to the divergence between the regions in all-cause mortality between 1991-93 and 2008-10 for men [increase in CV of SAM by 2% (0, 4%)], but not for women [decrease in CV of SAM by 15% (22, 10%)].

Differences in past smoking behaviour may largely explain the regional differences in all-cause mortality existing in 2008-10 in Poland, and its trends since 1991-1993.