Persistent and heterogeneous socioeconomic inequalities in women's malnutrition across 70 low- and middle-income countries.

BACKGROUND: Socioeconomic inequalities in malnutrition remain a major public health concern in low- and middle-income countries (LMICs). While patterns of undernutrition and excess weight are well documented, less is known about how their distribution across socioeconomic groups has changed over time. We aimed to examine cross-country patterns and descriptive temporal patterns of socioeconomic inequalities in women's nutritional status across LMICs. METHODS AND FINDINGS: We conducted a repeated cross-sectional analysis using the World Health Organization's Health Inequality Data Repository, which includes Demographic and Health Survey data from 70 LMICs between 1991 and 2023. National estimates of anemia, thinness, overweight, obesity, and combined overweight/obesity were analyzed by wealth and place of residence; education-based analysis was treated as exploratory due to limited coverage. Wealth-related inequality was measured using the slope index of inequality (SII). Year-specific summaries were calculated as unweighted medians across the countries observed in each calendar year, without interpolation. In country-specific latest surveys, the median wealth-related SII was as follows: -6.2 percentage points for anemia, -5.6 for thinness, +14.0 for overweight, +13.2 for obesity, and +25.0 for combined overweight/obesity. Among the countries with repeated observations, overweight, obesity, and combined overweight/obesity remained pro-advantaged in 89.7, 84.5, and 87.9% of country series, respectively; reversals in these trends occurred in only 6.9-8.6% of country series. Sensitivity analyses conducted on all available survey rounds generally found no clear linear change in the magnitude of inequality, although strengthening was more frequent for obesity. Overall, comparisons of repeated country observations showed a mixture of persistent, attenuating, strengthening, and reversing inequality patterns. Mixed-effects models supported overall differences across survey periods but highlighted substantial variability between countries. CONCLUSION: Socioeconomic inequalities in women's malnutrition were predominantly persistent in direction but heterogeneous in magnitude across countries. Deficiency-related outcomes remained concentrated among disadvantaged women, whereas overweight and obesity generally remained concentrated among advantaged women, with relatively uncommon reversal. These repeated cross-sectional findings support continuous monitoring of both nutritional burden and its socioeconomic distribution but do not directly identify the mechanisms responsible for the observed patterns.