Population based study to assess prevalence and risk factors of gastroesophageal reflux disease in a high altitude area.

AIM: We did a population-based cross-sectional study to investigate the prevalence and risk factors of gastroesophageal reflux disease (GERD) in a high altitude area. METHODS: An observational study using a validated questionnaire consisting of demographic, lifestyle and dietary characteristics was administered in an interview based format by two clinicians on a sample of adult population residing in urban area and rural high altitude areas of Ladakh. Presence of GERD was defined as a score of ≥4 using a previously validated symptom score based on the severity and frequency of heartburn and regurgitation. Other factors studied were body mass index (BMI), oxygen saturation levels by pulse oximetry and serum lipid profile. A multivariate analysis was done to find out risk factors for symptomatic GERD. RESULTS: Of the 905 subjects analyzed, there were 399 (44.1%) men; 469 (51.8%) were from rural background and 722 (79.8%) lived in areas 3,000 m above sea level. Symptomatic GERD was present in 169 (18.7%) subjects. Regurgitation occurred once a week in 34.8% and heartburn occurred in 42.9% of subjects. Sixteen (9.5%) had moderate-severe disease activity while 153 (90.5%) had mild disease. Three hundred and eighty-eight (42.7%) and 315 (34.8%) subjects had symptom of heartburn and regurgitation (at least once a week), respectively. On multivariate analysis, risk factors for GERD were age ≤50 years (OR: 1.508, 95% CI: 1.028-2.213), sedentary lifestyle (OR: 2.78, 95% CI: 1.016-7.638), lower intake of salt tea (OR: 1.663, 95% CI: 1.014-2.726); whereas the protective factors were no intake of meat (OR: 0.841, 95% CI: 0.715-0.990), intake of fresh fruits ≥1/week (OR: 0.631, 95% CI: 0.409-0.973), and serum LDL ≤150 mg/dL (OR: 0.435, 95% CI: 0.218-0.868). CONCLUSION: This population-based study in a high altitude area in India suggests a high prevalence (18.7%) of GERD. A younger age group, sedentary lifestyle, serum LDL >150 mg/dL, high consumption of meat, low consumption of salted tea and low consumption of fresh fruits were significant risk factors for development of GERD.

Adaptation and mal-adaptation to ambient hypoxia; Andean, Ethiopian and Himalayan patterns.

The study of the biology of evolution has been confined to laboratories and model organisms. However, controlled laboratory conditions are unlikely to model variations in environments that influence selection in wild populations. Thus, the study of "fitness" for survival and the genetics that influence this are best carried out in the field and in matching environments. Therefore, we studied highland populations in their native environments, to learn how they cope with ambient hypoxia. The Andeans, African highlanders and Himalayans have adapted differently to their hostile environment. Chronic mountain sickness (CMS), a loss of adaptation to altitude, is common in the Andes, occasionally found in the Himalayas; and absent from the East African altitude plateau. We compared molecular signatures (distinct patterns of gene expression) of hypoxia-related genes, in white blood cells (WBC) from Andeans with (n = 10), without CMS (n = 10) and sea-level controls from Lima (n = 20) with those obtained from CMS (n = 8) and controls (n = 5) Ladakhi subjects from the Tibetan altitude plateau. We further analyzed the expression of a subset of these genes in Ethiopian highlanders (n = 8). In all subjects, we performed the studies at their native altitude and after they were rendered normoxic. We identified a gene that predicted CMS in Andeans and Himalayans (PDP2). After achieving normoxia, WBC gene expression still distinguished Andean and Himalayan CMS subjects. Remarkably, analysis of the small subset of genes (n = 8) studied in all 3 highland populations showed normoxia induced gene expression changes in Andeans, but not in Ethiopians nor Himalayan controls. This is consistent with physiologic studies in which Ethiopians and Himalayans show a lack of responsiveness to hypoxia of the cerebral circulation and of the hypoxic ventilatory drive, and with the absence of CMS on the East African altitude plateau.