Demographic details of the twins studied
| Monozygotic twins (n=1856) | Dizygotic twins (n=2064) | p Value | |
|---|---|---|---|
| p values are corrected for relatedness of the twins. | |||
| *Mean (range). | |||
| †Excess alcohol intake defined as >28 units per week for a man and >21 units per week for a woman. | |||
| GORD, gastro-oesophageal reflux disease; HRT, hormone replacement therapy; GI, gastrointestinal. | |||
| Age (y) | 51 (19–81)* | 52 (20–82)* | 0.13 |
| Female | 91% | 93% | 0.05 |
| At least weekly GORD symptoms | 18% | 18% | 0.98 |
| Body mass index (kg/m2) | 25 (14–47)* | 25 (15–54)* | 0.01 |
| Ever smoked | 36% | 45% | <0.01 |
| Excess alcohol† | 5% | 6% | 0.54 |
| Anticholinergic drug therapy | 7% | 6% | 0.18 |
| Oral contraceptive or HRT | 24% | 26% | 0.17 |
| Parental family history of upper GI disease | 26% | 24% | 0.15 |
| Right handed | 88% | 88% | 0.92 |