Influence of homocysteine and genetic polymorphisms of methylenetetrahydrofolate reductase (MTHR), methionine synthase (MTR), methionine synthase reductase (MTRR), transcobalamin (TC) and apolipoprotein E (ApoE) on intelligence quotient (IQ; median (25th–75th centile)) in patients with Down’s syndrome
| Characteristic | n (%) | IQ | p value* | |
|---|---|---|---|---|
| Yes | No | |||
| *p values in bold are significant. | ||||
| Homocysteine >7.5 μmol/l (median) | 66 (50.3) | 35 (25–45) | 45 (35–55) | 0.0013 |
| Homocysteine >9.6 μmol/l (75th centile) | 34 (25.9) | 35 (20–45) | 40 (35–50) | 0.0021 |
| MTHFR 677 T allele | 85 (65.4) | 35 (30–46) | 45 (35–55) | 0.0165 |
| MTHFR 1298 C allele | 76 (58.0) | 40 (32–50) | 35 (25–50) | 0.2762 |
| MTR 2756 G allele | 52 (40.0) | 40 (32–50) | 35 (30–50) | 0.2849 |
| TCN 776 G allele | 95 (73.0) | 35 (30–50) | 40 (35–50) | 0.1895 |
| ApoE ε4 allele | 15 (11.7) | 45 (36–55) | 40 (30–50) | 0.1039 |
| MTHFR 677 T allele/MTHFR 1298 C allele | 39 (30.0) | 40 (30–45) | 40 (30–50) | 0.4251 |
| MTHFR 677 T allele/MTR 2756 G allele | 32 (24.6) | 40 (30–50) | 39 (30–56) | 0.9483 |
| MTHFR 677 T allele/TCN 776 G allele | 63 (48.5) | 35 (28–45) | 45 (35–54) | 0.0074 |
| MTHFR 677 T allele/ApoE ε4 allele | 10 (7.8) | 42 (35–45) | 40 (30–50) | 0.6222 |