Table 1. Characteristics of the Study Sample by Overall Home Environment Risk.
| Characteristics | Overall Higher-Risk Home Environment (n = 417) | Overall Lower-Risk Home Environment (n = 508) | P Value Differencea |
|---|---|---|---|
| Age at HEI, mean (SD), y | 4.13 (0.44) | 4.16 (0.37) | .19 |
| Sex of twin pair, No. (%) | |||
| Male | 147 (35.3) | 167 (32.9) | .74 |
| Female | 144 (34.5) | 180 (35.4) | |
| Opposite sex | 126 (30.2) | 161 (31.7) | |
| Zygosity, No. (%) | |||
| Monozygotic | 151 (36.2) | 163 (32.1) | .19 |
| Dizygotic | 266 (63.8) | 345 (67.9) | |
| Maternal educational level, No. (%)b | |||
| Low | 80 (19.2) | 56 (11.0) | <.001 |
| Medium | 170 (40.8) | 157 (30.9) | |
| High | 167 (40.0) | 295 (58.1) | |
| NSSEC, No. (%)c | |||
| Low | 75 (18.0) | 46 (9.1) | <.001 |
| Medium | 76 (18.3) | 62 (12.2) | |
| High | 265 (63.7) | 399 (78.7) | |
| Composite score, mean (range) | 0.81 (−0.03 to 4.02) | −0.70 (−2.44 to −0.03) | <.001 |
| Food score, mean (range) | 3.84 (−11.35 to 25.24) | −3.09 (−19.24 to 9.46) | <.001 |
| Activity score, mean (range) | 1.85 (−4.93 to 16.15) | −1.49 (−4.93 to 5.79) | <.001 |
| Media score, mean (range) | 1.86 (−6.45 to 18.12) | −1.81 (−7.00 to 4.37) | <.001 |
| 4-y BMI SD score, mean (SD) | −0.06 (1.05) | −0.02 (0.99) | .57 |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); HEI, Home Environment Interview; NSSEC, National Statistics Socio-economic Classification.
Characteristics of those living in higher-risk vs lower-risk home environments were compared using χ2 for categorical variables and t tests for continuously distributed variables. One twin was selected at random to avoid clustering effects.
Educational level categorized as low (no qualifications or basic high school education), medium (vocational or advanced high school education), and high (university-level education).
NSSEC level categorized as low (lower supervisory and technical occupations, routine or semiroutine occupations, never worked, and long-term unemployed), medium (intermediate occupations, small employers, and own-account workers), and high (higher and lower managerial and professional occupations).