Association between Healthy Eating Index and Mental Health in Middle-Aged Adults Based on Household Size in Korea

This study examined the association between dietary lifestyle and mental health outcomes among middle-aged individuals (40–60-year-olds) living alone, using the Korean Healthy Eating Index (KHEI). The participants were selected (1334 men and 2185 women) from the Korea National Health and Nutrition Examination Survey 2016–2018 and categorized into single/multi-person households. The KHEI scores were calculated based on the 24 h recall data of dietary intake. Among both sexes, single-person households had significantly lower subjective health status scores (p = 0.015 for men; p < 0.001 for women), lower EuroQol-5D index scores (p = 0.011 for men; p = 0.003 for women), and higher Patient Health Questionnaire-9 index scores (p = 0.004 for men; p < 0.001 for women), compared to multi-person households. Men had a higher risk of depression in single-person households compared to multi-person households (OR, 3.5; 95% CI, 1.2–10.1). For women, the ORs for stress perception with the first tertile group of KHEI scores in single-person and multi-person households compared to the third tertile group were 3.5 (95% CI, 1.3–9.0) and 1.4 (95% CI, 1.0–1.8), respectively. The results of this study are expected to be used as baseline data to establish nutrition, healthy eating behavior, and health policies for the middle-aged living alone.