Sociodemographic and clinical characteristics by subject group
| Group I (n=39) | Group II (n=22) | Group III (n=36) | |
| Sex (M/F) | 17/22 | 10/12 | 15/21 |
| Age (y) | |||
| Median | 47 | 53 | 49 |
| Range | 21–63 | 23–76 | 31–81 |
| Ethnicity (%) | |||
| Chinese | 28 | 18 | 27 |
| Other | 11 | 4 | 9 |
| Education | |||
| Below secondary | 14 | 7 | 12 |
| Secondary | 15 | 8 | 15 |
| Above secondary | 10 | 7 | 9 |
| Marital status | |||
| Married | 30 | 14 | 29 |
| Single | 5 | 4 | 5 |
| Divorced/widowed | 4 | 4 | 2 |
| Occupation1-150 | |||
| Non-manual | 12 | 13 | 18 |
| Manual | 8 | 0 | 4 |
| Unemployed | 19 | 9 | 14 |
| Duration of pain (months)1-151 | |||
| Mean (95% CI) | 27.0 (19.7–34.3) | 14.7 (7.2–22.3) | 8.2 (6.7–9.7) |
| Manometric findings | |||
| Normal | 32 | 16 | |
| Non-specific abnormalities | 6 | 5 | |
| Nutcracker oesophagus | 1 | 0 | |
| Diffuse oesophageal spasm | 0 | 1 |