Comparison of salivary Mucin 5B (MUC5B) secretion between heat-not-burn tobacco users and non-smokers

The use of heat-not-burn (HNB) tobacco is rapidly increasing, particularly in Japan; however, its health effects, especially on innate immunity in the oral mucosa, remain unclear. This cross-sectional study aimed to compare the secretion levels of mucin 5B (MUC5B), a mucin that forms a protective barrier role on the oral mucosal surface, between HNB tobacco smokers and non-smokers. MUC5B levels in stored saliva samples from 208 males (147 in the non-smoking group, 32 in the HNB tobacco group, 15 in the paper cigarette group, and 14 in the dual-use group) were measured using enzyme-linked immunoassay (ELISA). The primary outcome was the MUC5B secretion rate (μg/min = MUC5B concentration × saliva secretion rate). Significant differences in MUC5B secretion rates were observed among the four groups, with multiple comparisons showing significantly lower rates in the HNB tobacco and dual-use groups than in the non-smoking group (p = 0.042 and p < 0.001, respectively). The observed decrease in salivary MUC5B secretion is a concern, as it may comprise oral hygiene and immune function. From a public health perspective, these findings provide a basis to discourage the use and combined use of HNB tobacco.