The association between the Global Diet Quality Score and all-cause mortality in Black South African adults.

BACKGROUND

Modifiable risk factors for cardiovascular diseases (CVD) include diet quality. The Global Diet Quality Score (GDQS) was designed to provide a comprehensive diet quality assessment, yet very few studies have assessed its relationship with CVD and all-cause mortality, particularly in an African setting.

OBJECTIVE

We determined the association between the baseline total GDQS, GDQS positive (GDQS+) and GDQS negative (GDQS-) and all-cause and CVD mortality after 13 years of follow-up in Black South African adults (aged 30 to 70 years). GDQS+ reflects healthy food intake, while GDQS- is reverse-scored (higher scores indicating lower intake of unhealthy foods). Across all GDQS measures, higher scores indicate better diet quality.

METHODS

The baseline dietary data from the PURE-NWP-SA study was used to calculate the GDQS, with mortality outcomes recorded 13 years later. Cox proportional hazards models were applied, stratified by sex, age group and observation time tertiles. Models were adjusted for lifestyle factors and health status. Hazard ratios (HRs) were calculated for baseline GDQS tertiles.

RESULTS

The overall GDQS was low in both survivors and non-survivors, reflecting low intake of many GDQS healthy food groups, with only whole grains and liquid oils reaching desirable levels (to give maximum points to the GDQS+). Compared with Tertile (T1), participants in T3 of the GDQS+ had a lower risk of all-cause mortality (HR = 0.69; 95% CI: 0.56-0.86), whereas those in T3 of the GDQS- had a higher risk (HR = 1.39; 95% CI: 1.12-1.73). No associations were found with CVD mortality.

CONCLUSION

The GDQS is a valuable tool for investigating all-causes mortality risk in African populations through its GDQS+ sub-metric. However, caution is warranted when applying the GDQS in settings of dietary monotony or food insecurity, particularly the GDQS- sub-metric which gives maximum points for low intake/avoidance of unhealthy food groups.