This was a cross-sectional email survey among the members of the Finnish Pensioners` Federation (26,205 members who had an email address, with mean age of 72.7 years, and 63.5% females). The invitation, including information about the study, and the questionnaire were sent in April 2021. A reminder message was sent 2 weeks later. The responses were collected electronically. The decision to respond was considered as an informed consent. The study was approved by the Ethics Committee of Kuopio University Hospital (289/2015). Permission to conduct the study was obtained from the Finnish Pensioners` Federation. Patients were not involved in the design or conduct of this study.

There were 62 questions about age, socioeconomic status, smoking, alcohol consumption, recently experienced symptoms, general health, disorders diagnosed by a doctor, medications, and number of cough-related doctor’s visits during the past year. Asthma, chronic rhinosinusitis, gastro-esophageal reflux disease (GERD) and obstructive sleep apnea (OSA) were inquired by questions recommended for epidemiological studies [7,8,9,10,11]. Depressive symptoms were asked using the Patient Health Questionnaire-2 (PHQ-2) [12]. The 24 additional questions about current cough included details about cough frequency and duration, the Leicester Cough Questionnaire (LCQ) to investigate the cough-related quality-of-life, and number of doctor’s visits due to current cough. The questionnaire has been used in our previous email survey [13], and it was modified for this study.

Current cough was defined as presence of cough within 2 weeks. Acute, subacute, and chronic cough were defined by duration of current cough (< 3 weeks, 3–8 weeks, and > 8 weeks, respectively)[14]. Current asthma was defined as doctor’s diagnosis of asthma at any age and wheezing during the past year [7]. Chronic rhinosinusitis was present if there was either nasal blockage or discharge (anterior or posterior nasal drip), and either reduction/loss of smell or facial pain/pressure for at least 3 months during the past year [8].

GERD was defined as presence of heartburn or regurgitation at least once a week in the last 3 months [9]. OSA was defined as presence of ≥ 2 of the following features: Loud snoring, daytime tiredness, observed apneas and arterial hypertension [10, 11]. Somatic sum was defined as the sum (0–15) of experienced symptoms during the last month, excluding respiratory symptoms. Disorder sum (0–19) was defined as the number of medical conditions diagnosed by a doctor, excluding background disorders of chronic cough [6]. Depressive symptoms were present if PHQ-2 score was ≥ 3 [12]. Family history of chronic cough was defined as cough lasting > 8 weeks in parents or siblings. Trigger sum (0–15) was defined as the sum of external cough-triggering factors. Allergy was defined as self-reported allergy to animals, pollens, or food. Chronic sputum production was defined as cough with phlegm on most days or nights for ≥ 3 months of the year [15].

The main outcomes were any (≥ 1) cough-related doctor’s visit during the past year, repeated (≥ 3) cough-related doctor’s visits during the past year, any (≥ 1) doctor’s visit due to current cough, and repeated (≥ 3) doctor’s visits due to current cough. Cough-related doctor’s visits during the past year included all visits within the previous year that were due to all cough episodes, whereas doctor’s visits due to current cough included only visits during the current cough episode. The definition of repeated doctor’s visits as ≥ 3 is consistent with our previous work [4].

Descriptive data are shown as means and 95% confidence intervals. Chi-squared test, Mann–Whitney U-test and Kruskal–Wallis test was applied when appropriate. Bonferroni correction was applied for multiple comparisons. Bivariate association of the main outcomes and the following variables were analysed: Age, gender, body mass index, current smoking, ever smoking, alcohol consumption, years of education, income level, pet ownership, moisture damage exposure, acetylsalicylic acid intolerance, self-assessed heath status, family history of chronic cough, symptom sum, disorder sum, depressive symptoms, allergy, chronic obstructive pulmonary disease, chronic sputum production, bronchiectasis, pulmonary fibrosis, tuberculosis, sarcoidosis, current asthma, chronic rhinosinusitis, GERD, OSA, duration of current cough, LCQ total score (LCQt), LCQ domains, presence of any cough trigger, presence of a chemical cough trigger, and trigger sum. The variables were chosen in the multivariate analyses based on plausible association with doctor’s visits due to cough, prevalence of ≥ 2% in the study population regarding the etiological variables, and at least a suggestive association (p < 0.1) with the outcome variable. From the variables with strong interrelationships (symptom sum, disorder sum and self-assessed health status), one variable with the strongest bivariate association with the main outcome was included in the multivariate analysis. From the LCQ scores, only LCQt was included in the analyses because of strong interrelationships with the domains. The multivariate analyses were conducted using binary logistic regression with a backward directed stepwise process. A p-value < 0.05 was considered statistically significant, but suggestive associations (p < 0.1) are also presented. The analyses were conducted using SPSS v.27.