2018 Section 6 - Laryngology, Voice Disorders, and Bronchoesophalogy

TABLE 3 ] (Continued)

Ranking by OR

Ranking by PAR

OR (95% CI) a

P Value a

PAR b , %

Prevalence, %

Risk Factor

Risk Factor

Female sex

1.3 (0.90-1.9)

.16

50

Occupational exposure to dust/fumes

(5)

Asthma

1.3 (0.65-2.7)

.43

6

Asthma

(2)

Upper airway cough syndrome

1.1 (0.45-2.5)

.87

5

Gastroesophageal re fl ux disease

(1)

Gastroesophageal re fl ux disease

1.1 (0.61-2.0)

.74

9

Upper airway cough syndrome

( < 1)

Bronchiectasis

NA

NA

0

Bronchiectasis

NA

Risk factors were identi fi ed from the stepwise estimation process in the whole population (see Table 2 ) and entered with forced entry in never-, former, and current smokers. PAR values in parentheses indicate those risk factors, which were not signi fi cantly associated with chronic cough when adjusting for age, but were forced into the model. NA ¼ not applicable. See Table 2 legend for expansion of other abbreviation. a ORs and P values were by Wald test from logistic regression model adjusted for age. b PAR was calculated as ( f [OR ‒ 1]) / (1 þ f [OR ‒ 1]), where f is the frequency of the risk factor in the respective population and OR is the OR for chronic cough in the respective population. c Air fl ow limitation was FEV 1 /FVC < 70%. 12 d Abdominal obesity was waist-hip ratio $ 0.85 for women and $ 0.90 for men. 20

A recent meta-analysis found the prevalence of chronic cough to be 8% to 10%. 2 However, most of the included studies in the meta-analysis had important limitations, including the use of different de fi nitions of chronic cough and poor representativeness of the general population. Only three of the included studies used a de fi nition of cough lasting > 8 weeks and reported prevalences of 12% in the United Kingdom, 2% in Japan, and 1% in Nigeria. 4-6 To our knowledge, this is the fi rst study reporting the Leicester Cough Questionnaire from a general population cohort. Compared with reports from specialized clinics, the observed median total score of 17.3 from the general population seems high. 40-44 In contrast, specialized clinics have observed median and mean total scores of the Leicester Cough Questionnaire of 12.0 to 12.8, indicating more severe cough. 40-42,44 It is, however, likely that individuals with chronic cough from specialized clinics are more disabled with lower scores than individuals with chronic cough from the general population. A single study comprising selected individuals with classical asthma observed a median total score of 17.8, 43 which is comparable with the observed score in the present study. Another previous study from a specialized clinic compared the scores from individuals with chronic cough with the scores from individuals with different chronic respiratory diseases, including asthma, COPD, and bronchiectasis, and did not observe any differences. 44 Furthermore, although women seemed to be more affected than men, they only differed statistically regarding the physical domain. Others could also not observe a difference between men

never smokers and former smokers, it indicates that chronic cough caused by smoking is mostly reversible, in accordance with other previous observations. 11,29,30 Therefore, smoking cessation is mandatory in the management of patients with chronic cough. However, 36% of individuals with chronic cough were never- smokers, highlighting that in this population smoking was the underlying cause in a minority of cases. Interestingly, some of the identi fi ed risk factors in our study have not been described or encountered before, including low income, abdominal obesity, and low vegetable intake. All three of these may be interrelated and could represent poor socioeconomic status and inequality in the access to health care in general. On the other hand, abdominal obesity may be associated with obstruction. 36-38 An alternative explanation may be gastroesophageal re fl ux disease secondary to abdominal obesity. 5,39 Clinical guidelines recommend asthma, gastroesophageal re fl ux disease, upper airway cough syndrome, and eosinophilic bronchitis as the most important causes to consider in the diagnostic assessment of patients with chronic cough. 8-10 However, these were not the most important risk factors for chronic cough in this chronic cough by increasing local or systemic in fl ammation, 31-35 or by inducing mechanical

study. The discrepancy may lie in that the recommendations are based on reports from

specialized clinics, clearly highlighting the dif fi culty of extrapolation to general practice and the importance of the present fi ndings.

chestjournal.org

92