Context-specific drivers of non-regular long-lasting insecticidal net use in the Greater Mekong Subregion

BACKGROUND: Long-lasting insecticidal nets (LLINs) are essential for malaria prevention, yet consistent use remains suboptimal. This study assessed LLIN use and associated factors in Thailand and Myanmar across diverse transmission contexts. METHODS: We analyzed cross-sectional data from 13,459 individuals attending malaria service points in three districts in Thailand and two townships in Myanmar (2017-2024). LLIN use was categorized as daily, intermittent, or non-use. Logistic regression identified factors linked to non-regular use in each country. A directed acyclic graph (DAG) illustrated hypothesized causal pathways. RESULTS: Among 3,062 participants in Myanmar, 16.9% reported intermittent or non-use. Higher odds were observed among individuals aged 5-14 years (aOR = 1.87, 95% CI: 1.29-2.75), 15-34 years (aOR = 3.42, 95% CI: 2.07-5.67), and ≥ 35 years (aOR = 4.42, 95% CI: 2.50-7.86), Rakhine ethnicity (aOR = 3.54, 95% CI: 2.76-4.57), residence in Paletwa (aOR = 20.9, 95% CI: 5.29-109), uncertain malaria history (aOR = 8.03, 95% CI: 3.61-18.4), and Plasmodium falciparum infection (aOR = 2.87, 95% CI: 2.02-4.06). Among 10,397 participants in Thailand, 31.2% reported intermittent or non-use. Significant factors included older age (aOR = 2.73, 95% CI: 2.07-3.62 for 15-34 years), male sex (aOR = 1.73, 95% CI: 1.56-1.91), agricultural occupation (aOR = 1.42, 95% CI: 1.04-1.95), residence in Bannang Sata (aOR = 17.9, 95% CI: 14.4-22.4) or Saba Yoi (aOR = 34.4, 95% CI: 23.3-52.3), P. falciparum (aOR = 3.61, 95% CI: 1.71-7.78), P. vivax (aOR = 2.74, 95% CI: 2.38-3.17), and lower odds with uncertain malaria history (aOR = 0.49, 95% CI: 0.35-0.68). CONCLUSION: Non-regular LLIN use was common and linked to demographic, occupational, and clinical factors. Context-specific strategies are needed to improve adherence and support malaria elimination goals.