Geographic and socioeconomic variation of sodium and potassium intake in Italy: results from the MINISAL-GIRCSI programme

Francesco P Cappuccio, Chen Ji, Chiara Donfrancesco, Luigi Palmieri, Renato Ippolito, Diego Vanuzzo, Simona Giampaoli, Pasquale Strazzullo, Francesco P Cappuccio, Chen Ji, Chiara Donfrancesco, Luigi Palmieri, Renato Ippolito, Diego Vanuzzo, Simona Giampaoli, Pasquale Strazzullo

Abstract

Objectives: To assess geographic and socioeconomic gradients in sodium and potassium intake in Italy.

Setting: Cross-sectional survey in Italy.

Participants: 3857 men and women, aged 39-79 years, randomly sampled in 20 regions (as part of a National cardiovascular survey of 8714 men and women).

Primary outcome measures: Participants' dietary sodium and potassium intakes were measured by 24 h urinary sodium and potassium excretions. 2 indicators measured socioeconomic status: education and occupation. Bayesian geoadditive models were used to assess spatial and socioeconomic patterns of sodium and potassium intakes accounting for sociodemographic, anthropometric and behavioural confounders.

Results: There was a significant north-south pattern of sodium excretion in Italy. Participants living in southern Italy (eg, Calabria, Basilicata and Puglia >180 mmol/24 h) had a significantly higher sodium excretion than elsewhere (eg, Val d'Aosta and Trentino-Alto Adige <140 mmol/24 h; p<0.001). There was a linear association between occupation and sodium excretion (p<0.001). When compared with occupation I (top managerial), occupations III and IV had a 6.5% higher sodium excretion (coefficients: 0.054 (90% credible levels 0.014, 0.093) and 0.064 (0.024, 0.104), respectively). A similar relationship was found between educational attainment and sodium excretion (p<0.0001). When compared with those with a university degree, participants with primary and junior school education had a 5.9% higher urinary sodium (coefficients: 0.074 (0.031, 0.116) and 0.038 (0.001, 0.075), respectively). The socioeconomic gradient explained the spatial variation. Potassium excretion was higher in central regions and in some southern regions. Those in occupation V (low-skill workers) showed a 3% lower potassium excretion compared with those in occupation I. However, the socioeconomic gradient only partially explained the spatial variation.

Conclusions: Salt intake in Italy is significantly higher in less advantaged social groups. This gradient is independent of confounders and explains the geographical variation.

Keywords: EPIDEMIOLOGY; NUTRITION & DIETETICS; PREVENTIVE MEDICINE.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Figures

Figure 1
Figure 1
Observed median 24 h urinary sodium (left) and potassium (right) excretion by region. Red (green) indicates a high (low) level of 24 h urinary sodium (left) and potassium (right) excretion.
Figure 2
Figure 2
Effects of socioeconomic status by occupation (left panels) and by education (right panels) for sodium (top) and potassium (bottom) excretion. Note: Values are back log-transformed. Top managerial occupations and university degree were the reference levels for occupation and education, respectively. *Significant effect compared with the reference level at p<0.05. p For linear trends reported in the panels (excluding housewives).
Figure 3
Figure 3
Estimated mean maps (left) and 90% probability maps (right) of log-transformed 24 h urinary sodium excretion. Top panel shows the maps using model 1 with spatial effect only; the middle and bottom panels show results using models 4a and 4b with occupation and education, respectively. In the mean map, red (green) indicates a high (low) level of 24 h urinary sodium excretion. In the probability map, grey indicates a non-significant spatial effect, and white (black) indicates a significantly positive (negative) spatial effect at 90% credible level.

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