Table 1 Potential confounders, method and time of data collection, and level of analysis
From: Socio-demographic factors associated with pet ownership amongst adolescents from a UK birth cohort
Variable | Method and time of data collection | Levels |
|---|---|---|
Ownership of a Cat, Dog, Rabbit, Rodent, Bird, Fish, Tortoise/turtles and Horse ownership | Collected retrospectively at 11, 13, 15 and 18 years | No, yes |
Gender | Medical records at birth | Male or female |
Ethnicity of child | Carer questionnaire at 140 months (11 years) | White, mixed, Asian, black, other. Collapsed to ‘white’ and ‘other’ |
Number of people in household | Derived from mother’s questionnaire at 122 months (10 years) | 3, 4, 5+ |
Presence of an older sibling | Derived from mother’s questionnaire (child based) at 18 months | No, yes |
Maternal education | Mother’s questionnaire at 32 weeks gestation. Highest level indicated | CSE or no qualification (lowest), vocational, O level, A level, degree (highest) |
Paternal education | Mother’s questionnaire at 32 weeks gestation. Highest level indicated | CSE or no qualification (lowest), vocational, O level, A level, degree (highest) |
Maternal social class | Derived from mother’s questionnaire at 32 weeks gestation (occupation) | Professional (highest), Managerial and technical, Skilled: non-manual, Skilled: manual, Partly skilled, Unskilled (lowest) |
Paternal social class | Derived from mother’s questionnaire at 32 weeks gestation (occupation) | Professional (highest), Managerial and technical, Skilled: non-manual, Skilled: manual, Partly skilled, Unskilled (lowest) |
Maternal age at delivery | Clinical records | Continuous (years) OR < 21 years, 21–30 years, > 30 years |
Mother had pets as a child | Mother’s questionnaire at 33 months | No, not at all; Yes, part of time; Yes, always |
House type | Derived from mother’s questionnaire at 122 months (10 years) | Detached, semi-detached, end terrace, terraced, flat/room in someone else’s house/other |