Is obesity more likely among children sharing a household with an older child with obesity? Cross-sectional study of linked National Child Measurement Programme data and electronic health records

Background/objectives We identified household members from electronic health records linked to National Child Measurement Programme (NCMP) data to estimate the likelihood of obesity among children living with an older child with obesity. Methods We included 126 829 NCMP participants in four London boroughs and assigned households from encrypted Unique Property Reference Numbers for 115 466 (91.0%). We categorised the ethnic-adjusted body mass index of the youngest and oldest household children (underweight/healthy weight <91st, ≥91st overweight <98th, obesity ≥98th centile) and estimated adjusted ORs and 95% CIs of obesity in the youngest child by the oldest child’s weight status, adjusting for number of household children (2, 3 or ≥4), youngest child’s sex, ethnicity and school year of NCMP participation. Results We identified 19 702 households shared by two or more NCMP participants (% male; median age, range (years)—youngest children: 51.2%; 5.2, 4.1–11.8; oldest children: 50.6%; 10.6, 4.1–11.8). One-third of youngest children with obesity shared a household with another child with obesity (33.2%; 95% CI: 31.2, 35.2), compared with 9.2% (8.8, 9.7) of youngest children with a healthy weight. Youngest children living with an older child considered overweight (OR: 2.33; 95% CI: 2.06, 2.64) or obese (4.59; 4.10, 5.14) were more likely to be living with obesity. Conclusions Identifying children sharing households by linking primary care and school records provides novel insights into the shared weight status of children sharing a household. Qualitative research is needed to understand how food practices vary by household characteristics to increase understanding of how the home environment influences childhood obesity.

Index children were joined with children in dataset two using Stata's many to many joinby function, combining all pairwise combinations on common RALFs.Where an older child matched to multiple index children, only one random pair was retained (n=5,342).
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Figure S4 -
Figure S4 -Identifying all other household members at the time of the index child's NCMP measurement

Table S1 -
Sample characteristics of oldest National Child Measurement Programme participants in the householdThe distribution by sex, ethnic background and weight status was broadly representative of NCMP participants in the four local authorities as a whole.

Table S2 -
Weight status distribution of index children participating in the National Child Measurement Programme, using UK1990 clinical and International Obesity Task Force cut-offs 1 Confidence interval.

Table S3 -
Household characteristics of children living in households with two National Child Measurement Programme participants, by index child's weight status 1 BMJ Publishing Group Limited (BMJ) disclaims all liability and responsibility arising from any reliance Supplemental material placed on this supplemental material which has been supplied by the author(s) 1 National Child Measurement Programme (NCMP)-recorded body mass index (BMI) after application of ethnic-specific BMI adjustments, categorised according to UK1990 clinical reference standard: "underweight or healthy weight" (<91st centile), "overweight" (≥91st to <98th centile), or "obese" (≥98th centile). 2Confidence interval.

Table S5 -
Univariable and multivariable odds ratios estimating the likelihood of obesity 1 among index children living in households with two National Child Measurement Programme participants As recorded in the NCMP and, where missing, supplemented with ethnic background as recorded in the child's primary care electronic health record. 9 School year of participation in the National Child Measurement Programme (NCMP), Reception participants are aged 4-5 years and Year 6 participants are aged 10-11 years.10Academicyear of participation in the National Child Measurement Programme (NCMP).Academic years run from September to July.11Local authority of school where child participated in the NCMP.12Whether the youngest and oldest child were of the same or different sex.13Time difference, calculated in months, between the oldest and youngest child's NCMP measurements.Cells highlighted in bold indicate occasions where the estimates are significantly difference to the reference group in the multivariable models.BMJ Publishing Group Limited (BMJ) disclaims all liability and responsibility arising from any reliance Supplemental material placed on this supplemental material which has been supplied by the author(s) 1 National Child Measurement Programme (NCMP)-recorded body mass index (BMI) after application of ethnic-specific BMI adjustments, categorised according to UK1990 clinical reference standard: "obese" (≥98th centile). 2 adjusting for oldest child's weight status, number of children in the household, sex, ethnic background and school year.3Mutuallyadjustingfor the oldest child's weight status, number of children in the household, sex and ethnic background.4Mutuallyadjustingfor the oldest child's weight status, sex and ethnic background.5 Odds ratio.6Confidenceinterval.7National Child Measurement Programme (NCMP)-recorded body mass index (BMI) after application of ethnic-specific BMI adjustments, categorised according to UK1990 clinical reference standard: "underweight or healthy weight" (<91st centile), "overweight" (≥91st to <98th centile), or "obese" (≥98th centile).8