24-hour coughs per hour was defined as the average hourly cough frequency based on 24-hour sound recordings using a digital recording device (cough monitor). A longitudinal analysis of covariance (ANCOVA) model was applied to log-transformed cough data to determine geometric mean (GM) 24-hour coughs per hour at baseline and week 24. The GMR (Week 24 GM 24-hour coughs per hour divided by Baseline GM 24-hour coughs per hour) is reported.

All randomized participants who took at least 1 dose of study intervention, had available 24-hour cough data at baseline and at least one available post-baseline measurement during the treatment period.

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention.

All randomized participants who received at least one dose of study intervention during the 52-week treatment period. Per protocol, participants in the optional off-treatment observational period were not included. 3 participants randomized to placebo group who took 1 or more incorrect dose(s) of study drug were counted in the higher dose group of gefapixant received: 2 participants were analyzed in the gefapixant 15 mg group and 1 was analyzed in the gefapixant 45 mg group.

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention.

All randomized participants who received at least one dose of study intervention during the 52-week treatment period. Per protocol, participants in the optional off-treatment observational period were not included. 3 participants randomized to placebo group who took 1 or more incorrect dose(s) of study drug were counted in the higher dose group of gefapixant received: 2 participants were analyzed in the gefapixant 15 mg group and 1 was analyzed in the gefapixant 45 mg group.

Awake coughs per hour was defined as the average hourly cough frequency while the participant is awake, based on a 24-hour interval of sound recordings using a digital recording device (cough monitor). ANCOVA model was applied to log-transformed cough data to determine GM of awake coughs per hour at baseline and week 24. The GMR (Week 24 GM awake coughs per hour divided by Baseline GM awake coughs per hour) is reported.

All randomized participants who took at least 1 dose of study intervention, had available awake 24-hour cough data at baseline and at least one available post-baseline measurement during the treatment period.

The 19-item LCQ assessed the impact of chronic cough in three health-related quality of life (HRQoL) domains (physical, social and psychological). The LCQ is calculated as a mean score for each domain ranging from 1 to 7, with a total score ranging from 3 to 21. Higher scores indicate better HRQoL. A clinically meaningful improvement from baseline in HRQoL was defined as ≥1.3-point increase in the LCQ total score at Week 24. The percentage of participants (logistic regression model-based) with a ≥1.3-point increase in the LCQ total score at Week 24 is presented.

All randomized participants who had taken at least 1 dose of study intervention, had available LCQ data at baseline, and at least one available post-baseline measurement in the treatment period.

24-hour coughs per hour was defined as the average hourly cough frequency based on 24-hour sound recordings using a digital recording device (cough monitor). A clinically meaningful improvement from baseline is defined as a ≤-30% change (≥30% reduction) in 24-hour coughs per hour at week 24. The percentage of participants (logistic regression model-based) with a ≤ -30% change from baseline in 24-hour coughs per hour at Week 24 (≥30% reduction from baseline) is presented.

All randomized participants who took at least 1 dose of study intervention, had available 24-hour cough data at baseline and at least one available post-baseline measurement in the treatment period.

The 7-item CSD was used to record participants' daily cough frequency, cough intensity, and disruption due to cough. Each item was rated on an 11-point scale ranging from 0 (best) to 10 (worst); the total daily CSD score was the sum of these seven item scores (Min=0, Max=70). Mean weekly CSD total score was defined as the average of the mean total daily scores collected during the week prior to each visit. The percentage of participants (logistic regression model-based) with a ≤-1.3 point change from baseline in CSD at Week 24 (or ≥1.3 point reduction from baseline) is reported.

All randomized participants who had taken at least 1 dose of study intervention, had available CSD data at baseline, and at least one available post-baseline measurement in the treatment period.

The 7-item CSD was used to record participants' daily cough frequency, cough intensity, and disruption due to cough. Each item was rated on an 11-point scale ranging from 0 (best) to 10 (worst); the total daily CSD score was the sum of these seven item scores (Min=0, Max=70). Mean weekly CSD total score was defined as the average of the mean total daily scores collected during the week prior to each visit. The percentage of participants (logistic regression model-based) with a ≤-2.7 point change from baseline in CSD at Week 24 (or ≥2.7 point reduction from baseline) is reported.

All randomized participants who had taken at least 1 dose of study intervention, had available CSD data at baseline, and at least one available post-baseline measurement in the treatment period.

The VAS is a single-item questionnaire with the response on a 100- point scale ranging from 0 ("No Cough") to 100 ("Extremely Severe Cough"). Mean weekly VAS score was defined as the average of the VAS scores collected during the week prior to each visit. The percentage of participants (logistic regression model-based) with a ≤-30 mm change from baseline in cough severity VAS score at Week 24 is reported.

All randomized participants who had taken at least 1 dose of study intervention, had available VAS data at baseline, and at least one available post-baseline measurement in the treatment period.