Influence of age and gender on gastric acid secretion as estimated by integrated acidity in patients referred for 24-hour ambulatory pH monitoring

OBJECTIVES: Earlier studies have suggested that gastric acid secretion declines with age. Integrated acidity (IA) calculated from ambulatory 24-h pH studies provides an estimation of gastric acid secretion that is less cumbersome than nasogastric aspiration. The aim of this study was to calculate IA as a function of age and gender. METHODS: In a retrospective study, 753 ambulatory 24-h pH studies from 1994 to 2001 were analyzed. Subjects were classified according to nine age groups: <35 yr (n = 124), 35-39 yr (n = 90), 40-44 yr (n = 92), 45-49 yr (n = 111), 50-54 yr (n = 96), 55-59 yr (n = 61), 60-64 yr (n = 59), 65-69 yr (n = 42), and ≥70 yr (n = 64). Basal integrated acidity (BIA) was defined as IA between 12 midnight and 8 AM when no meals were consumed. Daytime and nocturnal IA/h was measured from 8 AM to 8 PM and from 8 PM to 8 AM. Postprandial IA (PIA) was measured for 2 h after the largest meal peak in each patient. RESULTS: Gender distribution was similar between groups (χ² = 6.42, 3 df, p = 0.093). Mean gastric pH was similar between genders (2.96 ± 1.36 women; 3.01 ± 1.42 men; p = 0.71). Women and men had similar BIA (361.1 ± 384.1 vs 434.6 ± 436.6 mmol/L/h, p = 0.10), daytime IA (33.5 ± 33.0 vs 34.1 ± 33.7 mmol/L, p = 0.90) and nocturnal IA (43.3 ± 42.1 vs 48.0 ± 46.6 mmol/L, p = 0.42), and PIA (38.2 ± 58.7 vs 36.0 ± 58.5 mmol/L/h, p = 0.47). Mean gastric pH, daytime and nocturnal IA, BIA, and PIA did not differ between age groups (p > 0.1). None of the parameters studied had a linear association with age (mean gastric pH, r = 0.106; BIA, r = -0.124; daytime IA, r = -0.046; nocturnal IA, r = -0.104; PIA, r = -0.117). CONCLUSION: Based on this study, we conclude that IA is unaffected by gender or age.