In Nigeria most studies on GERD were carried out on patients referred for upper gastrointestinal endoscopy where diagnosis was limited to patients with endoscopically defined lesions [12]. However, only about 50% of patients with GERD will have endoscopically detectable lesions [13, 14]. Therefore, the use of a patient-centred, symptom driven approach to diagnosis which is independent of endoscopic findings is more appropriate. The prevalence of GERD in a similar community-based study carried out in Nigeria was 26.34% which is comparable to 32.8% reported in this study though the studies were from different geo-political zones of Nigeria [15]. Even though the use of symptom-based questionnaire is advocated in the diagnosis of GERD, there are many of such questionnaires, each with its strength and weakness [16]. We decided to use Carlsson- Dent questionnaire though not validated but has been used by two previous studies in Nigeria [15, 17]. When compared with GERD Q, another commonly used GERD questionnaire. Carlsson-Dent questionnaire was found to be easier for patients to understand and answer although it detected less GERD in patients that were overweight and obese [18]. A Thai study found Carlsson-Dent questionnaire diagnosed GERD more than PH monitoring and endoscopy although a prospective, open label multi-centre Dutch study reported a poor diagnostic performance of Carlsson-Dent [19, 20].
GERD has been associated with many factors [21]. In this study, age had a significant association with GERD with participants between the age group of 19–22 years having reduced odds of having GERD compared with age groups 15–18 years and age group greater than 23 years.
Song et al. [22] reported an increased risk for GERD in overweight and obese subjects. However, in this study we found that there are increased odds of having GERD in both underweight and obese subjects. The association between GERD and underweight is surprising and we have no explanation for it. It may however be related to spices contents of food as suggested by Song et al. [22] .
Gastroesophageal reflux disease causes extra-oesophageal symptoms by direct and indirect mechanisms. The direct is by aspiration while the indirect is vagally mediated [23, 24].
Chronic cough is a known extra-oesophageal manifestation of GERD. The most common causes of chronic cough in non-smoking patients with normal chest radiographs, who are not on angiotensin converting enzyme (ACE) inhibitors are post nasal drip syndrome (PNDS), asthma, gastroesophageal reflux and chronic bronchitis [25]. In our study, 8.7% of the study population had chronic or recurrent cough while 15.9% had nocturnal cough. Poe et- al found that GERD alone accounted for cough in 13% of their study population, while in 56% of patients, it was a contributing factor to persistence of cough [26].
Gastroesophageal reflux disease is a known aetiology of laryngeal inflammation otherwise called laryngopharyngeal reflux (LPR) [27]. Symptoms of LPR include hoarseness, throat pain, cough, hawking, dysphagia, odynophagia and voice fatigue. However, these symptoms are nonspecific and can also be seen in other patients with postnasal drip and those exposed to allergens and smoke. In our study population, 37.7% of students with GERD had hoarseness and 10.1% of them had dysphagia. Dysphagia in these group of patients is likely due to GERD as there are no demographic or clinical features suggestive of other oesophageal diseases like carcinoma.
Asthma has a strong correlation with GERD and the conditions seem to induce each other. Both epidemiologic studies and physiologic testing with ambulatory 24-h pH monitoring have established association between GERD and asthma [27, 28]. In our study we found asthma-like symptoms in 17.4% of students with GERD. In studying the prevalence of GERD in asthma patients, Kijander et al. found that though 35% of GERD related patients did not express the typical reflux symptoms, they had abnormal oesophageal acid exposure by pH monitoring [29] Similarly, Legget et al. conducted a study assessing GERD in patients whose asthma was difficult to control using 24-h ambulatory pH probes [30] .They reported that 55% had reflux at the distal probe while 35% had proximal probe reflux [31]. They therefore submitted that reflux occurs commonly in asthma patients.
This study also showed that dental erosion is a significant finding in subjects with GERD. A larger percentage of study participants in this study had dental erosion which is due to the gastric acidity [32]. . A study by Oginni et al. [33] reported that tooth wear index (TWI) scores were higher in patients with GERD than in control subjects. The frequency of regurgitation and duration of gastroesophageal reflux directly influence the severity of dental erosion.
In addition, other oral features such coated tongue, Xerostomia and halitosis were reported in some of the study participants with GERD. Impaired lower esophageal sphincter function also results in gas and stomach contents entering the esophagus resulting in halitosis.
Our study has some limitations. Information on the lifestyles of the Participants were not collected in this study because two other studies had focused on GERD, diet and lifestyles in our population [15, 17] and we felt there was no need for repetition. Secondly, Participants in this study, being University students, cannot be said to be representative of the Nigerian population. Lastly, we studied extra-oesophageal manifestations in those diagnosed with GERD only. Extra oesophageal symptoms of GERD have been reported without the typical symptoms of heartburns and or GERD [34]. Though there is no gold standard test for the association between extraoesophageal symptom and GERD, it is necessary, in our opinion, to do oesophageal PH monitoring and or GI endoscopy with oesophageal biopsy to be able to attribute those features to GERD since these extra oesophageal symptoms are not pathognomonic of GERD [28]. In this study, we did not do either of oesophageal PH monitoring or upper GI endoscopy for the Participants.