The main finding of this study is a strong association between chronic cough and climacteric symptoms in postmenopausal women. The women in this study were a generally healthy cohort who mostly visited the outpatient department for preventive or prophylactic exams, as well as for menopausal complaints. Of the 200 postmenopausal women, 33% showed mild to severe symptoms of chronic cough for over 8 weeks. When comparing these women to the women with chronic cough both cohorts did not differ in baseline characteristics such as age, weight, number of diseases or years since onset of menopause (Table 1). In the affected women, the cough started at an average of 3.5 years after entering menopause.
Chronic cough was clearly associated with an increase of menopausal symptoms and especially in regard to the subscales of the MRS II that mirror urogenital and somato-vegetative symptoms (Table 3, Fig. 1, Table 4). In addition, the results of the MRS and LCQ correlated with one another (Table 7). Furthermore, a significant prediction for chronic cough based on two somatic MRS domains and the total score could be shown (Table 8). These results contribute well to the biologically plausible theory that changes in the skin and mucous membranes can also show up in the respiratory tract, can change the sensitivity of the cough receptors and thus lead to increased cough sensitivity. The skin and mucous membranes represent an organ that can be influenced by hormonal changes. Decreasing estrogen level influence skin's glycosaminoglycan content and promote tendency to create wrinkles, dryness, atrophy and poor wound healing [33, 34]. The collagen content of the skin is significantly reduced by 1–2% per year after menopause . Some of these changes might also affect the respiratory system, a fact that was not yet the focus of either pulmonologists or gynecologists. Furthermore, lung function is strongly influenced by the female cycle and menopause [21, 27].
Chronic cough is a multifactorial symptom that can be the consequence of several pulmonary and extrapulmonary diseases including gastrooesophageal reflux, upper airway cough syndrome, obstructive sleep apnea, and medications such as ACE inhibitors [10,37–40). However, in a number of patients the genesis of chronic cough remains unclear, despite extensive diagnostics, then it is defined as chronic cough of unclear etiology or as chronic idiopathic cough (CIC). The clinical complaints of CIC, sometimes persisting for years, are a dry and excruciating cough, the urge to clear the throat and dysphagia [1, 2]. According to recent literature, idiopathic cough occurs in up to 20–42% of cases of chronic cough and can be triggered by weak subclinical triggers such as gastric acid, thermal stimuli, or passive smoking . In most cases, chronic idiopathic cough is difficult to treat as it does not respond to classic therapeutic options. Most patients treated in a cough clinic are not only female, but also postmenopausal [1, 16]. Due to the reaction to subclinical triggers, the clinical picture of chronic idiopathic cough is causally associated with cough hypersensitivity syndrome, which defines a disturbance in the sensory nerve function. The concept of hypersensitivity is described as a valid and clinically useful concept and can be seen as a neuropathy of the cough reflex [42, 46]. Accordingly, the cough receptors’ increased sensitivity and the changed central cough modulations lead to hyperreactivity of the cough reflex [33, 34]. In postmenopausal women, the chronic cough stimulus is also due to the cough receptors’ increased sensitivity and/or a changed central cough modulation [12–16]. However, according to the definition, no CIC can be assigned to the patients in this study, as they did not go through the necessary diagnostics.
The highly significant correlation of postmenopausal symptoms, especially the somato-vegetative subgroup and vaginal dryness and coughing, underline these assumptions and emphasize the need to further expand the complexity of the climacteric syndrome. Chronic (idiopathic) cough might be, in part, due to the lack of steroids in postmenopausal women and could be diagnosed and treated differently in the future. Further studies are needed to clarify the connections, the underlying pathomechanisms, and the effects of hormonal replacement therapy on the bronchopulmonary symptoms.
A limitation of this study it that it is a simple interview and questionnaire-based study with no additional information on individual findings such as mucus parameters, x-rays etc. On the other hand, a strength of this study is that a reasonable and well-selected representative number of patients was involved. Also, the groups appeared to be well-balanced to baseline characteristics, the effects shown are statistically substantiated and the questionnaires that were used are validated and established tools to measure the aimed effects. At first glance a rate of 33% of rather healthy postmenopausal patients that report coughing might seem high and was a surprising finding. On the other hand, existing cough was mainly defined by the time aspect of 8 weeks and most women reported rather mild symptoms. The LCQ values are lower in patients with COPD and chronically productive cough .
Therefore postmenopausal women might not be aware of their symptoms or relate them to their postmenopausal changes.
In addition, there is disagreement about the exact prevalence of chronic cough [48, 49].