Table 2.

Primary Studies on the Biologic Effects of E‐Cigarettes on the Upper Aerodigestive Tract and Ear in Human E‐Cig Users

References	Subject of interest	Study design	Number of e‐cig users	Outcome(s)
Alqahtani et al 200	Saliva	Cross‐sectional	14	Elevated inflammatory cytokines, differential expression of metabolites
Bustamante et al 64	Saliva	Cross‐sectional	16	Elevated levels of carcinogen N′‐nitrosonornicotine (NNN)
Cichońska et al 205	Saliva	Cross‐sectional	40	Decreased lysozyme and increased lactoferrin, no difference in IgA
Flieger et al 58	Saliva	Cross‐sectional	8	Elevated levels of thiocyanate
Franco et al 171	Oral epithelial cells	Cross‐sectional	22	No significant increase in micronuclei
Hamad et al 201	Buccal cells and blood	Self‐controlled	3	Differential gene expression
Martin et al 202	Nasal epithelial cells	Cross‐sectional	12	Differential gene expression (especially suppression of immune‐related genes)
Pushalkar et al 185	Saliva	Cross‐sectional	40	Altered oral microbiome, nonsignificant but considerable alterations in inflammatory cytokines
Rebuli et al 203	Nasal epithelial cell	Clinical trial	15	Suppression of IgA in setting of viral inoculation, differential gene expression, differential cytokine levels
Schwarzmeier et al 204	Oral epithelial cells	Cross‐sectional	20	Increased metanuclear abnormalities
Stewart et al 206	Saliva and buccal swab	Cross‐sectional	10	No significant differences in oral microbiome
Tommasi et al 199	Oral epithelial cells	Cross‐sectional	42	Differential gene expression