Although past studies have speculated that a relationship between depressive mood and chronic cough exists, this is the first to examine whether the relationship is causal and if smoking status, one of the most common causes of chronic cough, is associated in the general Korean population.
“Physicians should assess patients presenting with a chronic cough, particularly those who are female, for psychiatric disturbances, which will aid in determining the appropriate treatment to reduce the chronic cough,” wrote the investigators.
In the observational study, the investigators incorporated data from the Korea National Health and Nutrition Examination Survey for 2014 and 2016. The survey included information on demographics, smoking status, comorbidities, activity limitations, lung function, depressive mood, quality of life, and cough status.
To be considered for enrollment participants had to be aged 18 or older and complete all questionnaires, including the Patient Health Questionnaire-9 (PHQ-9) to assess severity of depressive symptoms and EuroQol Five-Dimension Questionnaire (EQ5D) to assess quality of life. For both questionnaires, higher scores indicated a greater burden.
Among the 15,700 people identified, of whom 7550 were from 2014 and 8150 were from 2016, 6175 eligible participants completed the questionnaires and were enrolled in the study. Ninety-five percent (n = 5949) of enrolled participants had no cough and 5% (n = 226) had a chronic cough for over 3 months.
Patients with chronic coughs were typically older, male, current smokers, and had worse lung function than participants without chronic cough. The proportion of cases of asthma (7.1%) or chronic obstructive pulmonary disease (COPD) (12.8%) were higher in the chronic cough group than the nonchronic cough group (1.4% and 0.7%, respectively).
Scores for the PHQ-9 were significantly higher among the patients in the chronic cough group than those in the nonchronic cough group (4.29 [5.23] vs 2.40 [3.53]; P < .001). EQ5D scores were also higher in the chronic cough group.
There were no significant differences in PHQ-9 scores between the chronic cough group and the nonchronic cough group among male participants (3.18 [4.27] vs 2.31 [3.65]; P = .092). However, significant differences were observed among female participants (5.69 [5.96] vs 3.05 [3.97]; P =< .001).
Among the participants with normal lung function, significant differences in PHQ-9 scores were observed between the chronic cough group and the nonchronic cough group (4.32 [5.32] vs 2.78 [3.86]; P = .003). A similar, yet smaller, effect was observed among participants with reduced lung function (4.19 [4.93] vs 2.11 [3.55]; P =< .001).
“This finding shows that a high depressive mood score in chronic cough participants is independent of smoking and underlying lung function, which suggests that a depressive mood might trigger a chronic cough in the general population,” noted the investigators.
When the investigators conducted univariate and multivariate logistic regression analyses, chronic cough was found to have a significant association with PHQ-9 scores (odds ratio [OR], 1.06; 95% CI, 1.014–1.27; P = .014), COPD (OR, 4.87; 95% CI, 1.041–22.86; P = .044), and bronchial asthma (OR, 2.93; 95% CI, 1.162–7.435; P = .023).
The investigators offered several possible explanations for chronic cough to be caused by depressive mood or depression. Tingling sensation or discomfort in the throat is sometimes cited by people with depression, which can lead to increased coughing as a method to clear throat discomfort. Additionally, gastroesophageal reflux disorders are more common in patients with depressive disorders and may cause chronic cough.
To help explain the sex differences detected in the study, the investigators pointed to studies that have indicated female patients have higher occurrences in cough reflex sensitivity and idiopathic chronic cough. The findings suggested that women may have a higher degree of depressive mood and are potentially more susceptible to developing chronic cough.
Study limitations included a potential over- or underestimation of health and disease status because of the cross-sectional nature of the study. Additionally, specific causes of chronic cough were not examined.
“We believe that there could have been a difference in the degree of depressive mood according to the underlying medical illness and cause of the chronic cough,” said the investigators.
Heo IR, Kim J-Y, Go S-I, et al. Chronic cough is associated with depressive mood in women regardless of smoking status and lung function. Clin Respir J. Published online March 14, 2021. Accessed April 1, 2021. doi: 10.1111/crj.13357