Study	Reason for exclusion
Boeree 1998	The majority of participants were people with asthma, and the rate of people with COPD was considered to be very low.
Kiljander 2000	Type of study population does not meet inclusion criteria: people with chronic persistent cough for two months or longer.
Liu 2018	Type of Intervention does not meet inclusion criteria: antireflux treatment administered was a combination of oral antacids (omeprazole) and mosapirde, a gastroprokinetic agent.
Miller 2015	Types of population and intervention do not meet inclusion criteria; oral danirixin in healthy male subjects.
NCT00214552	Type of population does not meet inclusion criteria: people with asthma only.
NCT00523367	Non‐RCT: single‐arm study
Sun 2016	Type of intervention does not meet inclusion criteria: combination of oral antacid (esomeprazole) with oral mosapride and tiotropium bromide.
UMIN000002056	The trial was registered but not conducted.

COPD: chronic obstructive pulmonary disease; RCT: randomised controlled trial