Cut-offs for childhood BMI in prediction of cardiovascular disease risk factors in adulthood Leah Li MRC Centre of Epidemiology for Child Health UCL Institute of Child Health Utility of cut-offs for childhood BMI in the prediction of cardiovascular disease risk factors in adulthood Imperial College, 16 Nov 2011

(obese children more likely to become obese adults) Childhood BMI Trends in child obesity in recent decades BMI tracks from childhood to adulthood (obese children more likely to become obese adults) Adult obesity linked to increased risks of CVD, type 2 diabetes This raises issue as to whether individuals with high risk of adult disease can be identified from their BMI in childhood Links between childhood obesity and future health outcomes? Obese children are known to be more likely to become obese adults than non-obese children. In turn, the health consequences of adult obesity include increased risk of developing chronic disease, such as CVD, type 2 diabetes. Prevention of such health consequences is therefore a priority, and raises the issue as to whether those with high risk of adult disease can be identified from their BMI in childhood. There are still considerable gaps in knowledge of the links between childhood obesity and future health outcomes. Cut-off points for childhood BMI become crucial for identifying children with increased health risk as adults, but to date there has been only limited evaluation of the available BMI reference standards for children.

Reference standards for child BMI Most based on age- gender-specific BMI distribution IOTF cut-offs‡ - correspond to percentile curves for 18y BMI of 25 & 30 kg/m2 Percentile (85th, 90th)† - arbitrary Defined within reference population, not directly linked to adult health outcomes Internally derived cut-offs for child BMI (population specific) (require data on BMI in childhood and disease risks in adulthood) Adult cut-offs correlate with markers of obesity-related diseases, IOTF cut-offs for child overweight/obesity not directly linked to later health outcomes. How well the IOTF cut-offs predict children at risk of adult disease is not clear Few examined how well these cut-offs predict long-term outcomes in population-based studies. † Kuczmarski et al CDC growth charts 2001 ‡ Cole et al 2000

Study sample 1958 British Birth Cohort - born in Great Britain in one week, Mar 1958 (≈17,000), followed up to 50y. Medical assessment at 45y (n=9,377) Childhood BMI (kg/m2) at 7, 11, 16y CVD risk factors at 45y: Obesity (BMI ≥ 30 kg/m2) Abdominal obesity (waist ≥ 102/88 cm) High risk of type 2 diabetes (HbA1c 7%; on medication; reported type 2 diabetes; excluding T1 diabetes) Hypertension ( ≥ 140/90 mmHg; on medication) Low HDL-C ( < 1/1.3 mmol/l) High LDL-C ( > 4.13 mmol/l) High triglycerides ( ≥ 2.3 mmol/l)

CVD risk factors at 45y in 1958 cohort Males Females Overweight 49.7 % 32.7 % Obese 25.2 % 23.5 % Abdominal obesity 36.9 % Type 2 diabetes or HbA1c ≥7% 3.7 % 2.4 % Hypertension‡ 34.6 % 16.3 % Low HDL 9.3 % 19.6 % High LDL 24.4 % 14.8 % High triglycerides 41.5 % 16.0 % Obesity, hypertension, high triglycerides and LDL-cholesterol were the most common CVD risk factors at 45y.

Childhood BMI IOTF cut-offs (%) Males Females Overweight@7 18.2(5.5) 18.0(7.2) Obese@7 21.1(0.8) 21.0(1.6) Overweight@11 20.9(6.0) 21.2(7.9) Obese@11 25.6(0.8) 26.1(1.1) Overweight@16 23.9(6.3) 24.4(9.3) Obese@16 28.9(1.4) 29.4(1.2) Overweight@45 25.0(49.7) 25.0(32.7) Obese@45 30.0(25.2) 30.0(23.5) Based on the IOTF cut-offs, 6.3-10.5% of cohort members were classified as overweight or obese between ages 7 and 16y. At age 45y, 74.9% of men and 56.2% of women were overweight or obese.

Childhood BMI IOTF cut-offs (%) Males Females Overweight@7 18.2(5.5) 18.0(7.2) Obese@7 21.1(0.8) 21.0(1.6) Overweight@11 20.9(6.0) 21.2(7.9) Obese@11 25.6(0.8) 26.1(1.1) Overweight@16 23.9(6.3) 24.4(9.3) Obese@16 28.9(1.4) 29.4(1.2) Overweight@45 25.0(49.7) 25.0(32.7) Obese@45 30.0(25.2) 30.0(23.5) At 7-16y, 6.3-10.5% classified as overweight or obese Based on the IOTF cut-offs, 6.3-10.5% of cohort members were classified as overweight or obese between ages 7 and 16y. At age 45y, 74.9% of men and 56.2% of women were overweight or obese. 7

Childhood BMI IOTF cut-offs (%) Males Females Overweight@7 18.2(5.5) 18.0(7.2) Obese@7 21.1(0.8) 21.0(1.6) Overweight@11 20.9(6.0) 21.2(7.9) Obese@11 25.6(0.8) 26.1(1.1) Overweight@16 23.9(6.3) 24.4(9.3) Obese@16 28.9(1.4) 29.4(1.2) Overweight@45 25.0(49.7) 25.0(32.7) Obese@45 30.0(25.2) 30.0(23.5) At 7-16y, 6.3-10.5% classified as overweight or obese HSE06-08: 21% boys, 24% girls (9-11y) were overweight or obese Based on the IOTF cut-offs, 6.3-10.5% of cohort members were classified as overweight or obese between ages 7 and 16y. At age 45y, 74.9% of men and 56.2% of women were overweight or obese. 8

Childhood BMI IOTF cut-offs (%) Males Females Overweight@7 18.2(5.5) 18.0(7.2) Obese@7 21.1(0.8) 21.0(1.6) Overweight@11 20.9(6.0) 21.2(7.9) Obese@11 25.6(0.8) 26.1(1.1) Overweight@16 23.9(6.3) 24.4(9.3) Obese@16 28.9(1.4) 29.4(1.2) Overweight@45 25.0(49.7) 25.0(32.7) Obese@45 30.0(25.2) 30.0(23.5) At 7-16y, 6.3-10.5% classified as overweight or obese ages. At 45y, 74.9% men, 56.2% women were overweight or obese. Based on the IOTF cut-offs, 6.3-10.5% of cohort members were classified as overweight or obese between ages 7 and 16y. At age 45y, 74.9% of men and 56.2% of women were overweight or obese.

ROC curves of predicting obesity 45 from child BMI (Males & females) Receiver Operating Characteristic analysis to assess prediction of each adult CVD risk factor from BMI at 7, 11, and 16y.   Diagnostic sensitivity (probability of true positive) and specificity (probability of true negative) of the IOTF cut-offs for childhood overweight and obesity combined to assess how well they predicted each adult CVD risk factor. ROC analysis (AUC) to assess how well BMI at each age predicts adult obesity

ROC curves of predicting obesity 45 from child BMI (Males & females) AUC increase with age BMI16 was best predictor for adult obesity. Greater increase in AUC (7-11). Than (11-16) Receiver Operating Characteristic analysis to assess prediction of each adult CVD risk factor from BMI at 7, 11, and 16y.   Diagnostic sensitivity (probability of true positive) and specificity (probability of true negative) of the IOTF cut-offs for childhood overweight and obesity combined to assess how well they predicted each adult CVD risk factor. ROC analysis (AUC) to assess how well BMI at each age predicts adult obesity

Prediction of adult CVD risk factors from child BMI IOTF cut-offs Sensitivity Specificity Obese 7 15.3 94.8 (BMI≥30) 11 19.5 95.8   16 24.8 95.9 Abdominal 13.0 95.2 obesity 15.7 96.3 19.0 96.1 Type 2 15.9 92.8 diabetes 24.2 31.5 92.0

Prediction of adult CVD risk factors from child BMI IOTF cut-offs Sensitivity Specificity Obese 7 15.3 94.8 (BMI≥30) 11 19.5 95.8   16 24.8 95.9 Abdominal 13.0 95.2 obesity 15.7 96.3 19.0 96.1 Type 2 15.9 92.8 diabetes 24.2 31.5 92.0 Prediction improved with increasing childhood age HIGH specificities, but VERY LOW sensitivities for predicting adult outcome, only 4.1-5.2% of non-obese adults were classified as overweight/obese as a child. A substantial proportion of obese adults >75.2% classified as non-overweight as a child. Similar for abdominally obese and high diabetes risk at 45y

Prediction of adult CVD risk factors from child BMI IOTF cut-offs Sensitivity Specificity Hypertension 7 8.3 92.7   11 10.6 93.1 16 12.5 92.2 High LDL 7.6 92.5 8.2 92.4 8.5 91.6 Low HDL 10.1 93.0 11.8 14.6 High trig 7.1 8.0 92.6 10.0 92.0 Childhood BMI was a weak predictor for adult hypertension, adverse lipids Childhood BMI was a weak predictor for adult hypertension and adverse lipid levels Similarly, the specificities for IOTF cut-offs were high (91.6-93.1%), and sensitivities were relatively low (7.1 to 14.6%).

Internal cut-offs for child BMI for predicting adult CVD risk factors 15.6-17.6 (15.6-51.9%) BMI@11 16.2-20.5 (25.0-54.7%) BMI@16 19.3-24.3 (21.2-55.5%)

Internal cut-offs for child BMI for predicting adult CVD risk factors 15.6-17.6 (15.6-51.9%) BMI@11 16.2-20.5 (25.0-54.7%) BMI@16 19.3-24.3 (21.2-55.5%) Internal cut-offs for 1958 cohort , identifying for each CVD risk factor to achieve max combination of sensitivity & specificity Varied according to adult factors, lower than IOTF cut-offs, identified larger proportions of population in childhood as having increased risk of adult CVD risks

Childhood BMI cut-offs for predicting adult CVD risk factors IOTF cut-offs (%) Internal cut-offs (%) Males Females Childhood BMI Overweight@7 18.2(5.5) 18.0(7.2) 15.6-17.6 (15.6-51.9%) Obese@7 21.1(0.8) 21.0(1.6) Overweight@11 20.9(6.0) 21.2(7.9) 16.2-20.5 (25.0-54.7%) Obese@11 25.6(0.8) 26.1(1.1) Overweight@16 23.9(6.3) 24.4(9.3) 19.3-24.3 (21.2-55.5%) Obese@16 28.9(1.4) 29.4(1.2) Based on the IOTF cut-offs, 6.3-10.5% of cohort members were classified as overweight or obese between ages 7 and 16y. At age 45y, 74.9% of men and 56.2% of women were overweight or obese.

Prediction of adult CVD risk factors from child BMI Study specific cut-offs   Sensitivity Specificity Obese 7 61.5 61.8 (BMI≥30) 11 66.1 67.7   16 67.3 70.6 Abdominal 51.2 65.2 obesity 54.7 72.1 59.2 68.5 Type 2 41.9 76.6 diabetes 49.5 73.0 60.2 71.6 Individuals with a child BMI above internal cut-offs had increased adult CVD risks. E.g. 38.4% of individuals with a BMI16 above cut-offs (20.5 kg/m2 for boys; 21.3 kg/m2 for girls) had an increased risk for adult obesity: OR=5.0. For elevated risk of type 2 diabetes, 29.4% individuals whose BMI16 above cut-offs (20.4 and 23.1 kg/m2) had an increased diabetes risk: OR= 3.8. 

Prediction of adult CVD risk factors from child BMI Study specific cut-offs   Sensitivity Specificity Obese 7 61.5 61.8 (BMI≥30) 11 66.1 67.7   16 67.3 70.6 Abdominal 51.2 65.2 obesity 54.7 72.1 59.2 68.5 Type 2 41.9 76.6 diabetes 49.5 73.0 60.2 71.6 Lower specificities than IOTF cut-offs, improved sensitivities Obesity: 29.4% non-obese adults identified as at-risk, 32.7% obese adults not identified using internal cut-offs for BMI16. Diabetes: 23.4-28.4% adults with low diabetes risk identified as above BMI cut-offs in childhood, while 39.8-58.1% adults with high diabetes risks not identified. Individuals with a child BMI above internal cut-offs had increased adult CVD risks. E.g. 38.4% of individuals with a BMI16 above cut-offs (20.5 kg/m2 for boys; 21.3 kg/m2 for girls) had an increased risk for adult obesity: OR=5.0. For elevated risk of type 2 diabetes, 29.4% individuals whose BMI16 above cut-offs (20.4 and 23.1 kg/m2) had an increased diabetes risk: OR= 3.8. 

Prediction of adult CVD risk factors from child BMI Study specific cut-offs Sensitivity Specificity Hypertension 7 39.0 69.7   11 55.7 56.1 16 44.8 73.9 High LDL 17.3 84.6 31.6 76.6 25.1 79.8 Low HDL 52.1 52.9 54.9 54.2 39.1 78.0 High trig 39.6 60.2 42.2 67.4 24.5 71.2

Prediction of adult CVD risk factors from child BMI Study specific cut-offs Sensitivity Specificity Hypertension 7 39.0 69.7   11 55.7 56.1 16 44.8 73.9 High LDL 17.3 84.6 31.6 76.6 25.1 79.8 Low HDL 52.1 52.9 54.9 54.2 39.1 78.0 High trig 39.6 60.2 42.2 67.4 24.5 71.2 Childhood BMI - weak predictor for adult hypertension and adverse lipids

Prediction of adult CVD risk factors from child BMI IOTF cut-offs Study specific cut-offs   Sensitivity Specificity AUC (95% CI) Obese 7 15.3 94.8 61.5 61.8 0.65(0.64,0.67) (BMI≥30) 11 19.5 95.8 66.1 67.7 0.72(0.71,0.73)   16 24.8 95.9 67.3 70.6 0.75(0.74,0.77) Abdominal 13.0 95.2 51.2 65.2 0.61(0.59,0.62) obesity 15.7 96.3 54.7 72.1 0.68(0.66,0.69) 19.0 96.1 59.2 68.5 0.69(0.68,0.71) Type 2 15.9 92.8 41.9 76.6 0.59(0.54,0.63) diabetes 24.2 49.5 73.0 0.65(0.60,0.69) 31.5 92.0 60.2 71.6 0.68(0.63,0.72) Prediction improved with increasing childhood age IOTF cut-offs: high specificities, but VERY LOW sensitivities for predicting adult outcome. Specificities for adult obesity (94.8-95.9%) indicate - only 4.1-5.2% of non-obese adults were classified as overweight/obese as a child. A substantial proportion of obese adults (75.2-84.7%) classified as non-overweight as a child. Similar for abdominally obese and high diabetes risk at 45y Study-specific cut-offs for adult risk factor provided lower specificities than IOTF cut-offs, but improved sensitivities For predicting adult obesity, specificity & sensitivity for internally derived cut-offs ranged 61.8-70.6% and 61.5- 67.3%. E.g. 29.4% non-obese adults identified as at-risk and 32.7% obese adults not identified using internal cut-offs for BMI16. By definition, internal cut-offs had a higher combination of sensitivity & specificity than IOTF (e.g. 137.9 v 120.7 for BMI16). Similar cut-off points were found for predicting abdominal obesity. For diabetes, specificities 71.6-76.6% indicate 23.4-28.4% adults with low diabetes risk were identified as above the BMI cut-off in childhood, while sensitivities from 41.9 to 60.2% indicate that 39.8-58.1% adults with high diabetes risks were not identified as above the BMI cut-offs in childhood. Internal cut-offs varied according to adult factors, were lower than IOTF cut-offs, therefore identified larger proportions of the population in childhood as having increased risk of adult CVD outcomes (15.6-55.5% vs 6.3-10.5%). Individuals with a child BMI above internal cut-offs had increased adult CVD risks. E.g. 38.4% of individuals with a BMI16 above cut-offs (20.5 kg/m2 for boys; 21.3 kg/m2 for girls) had an increased risk for adult obesity: OR=5.0. For elevated risk of type 2 diabetes, 29.4% individuals whose BMI16 above cut-offs (20.4 and 23.1 kg/m2) had an increased diabetes risk: OR= 3.8.  Li et al. Am J Clin Nutri (2011)

Prediction of adult CVD risk factors from child BMI IOTF cut-offs Study specific cut-offs Sensitivity Specificity AUC (95% CI) Hypertension 7 8.3 92.7 39.0 69.7 0.53(0.52,0.55)   11 10.6 93.1 55.7 56.1 0.54(0.52,0.55) 16 12.5 92.2 44.8 73.9 0.54(0.52, .55) High LDL 7.6 92.5 17.3 84.6 0.50(0.49,0.52) 8.2 92.4 31.6 76.6 0.51(0.49,0.53) 8.5 91.6 25.1 79.8 0.51(0.49,0.52) Low HDL 10.1 93.0 52.1 52.9 0.54(0.51,0.56) 11.8 54.9 54.2 0.57(0.55,0.59) 14.6 39.1 78.0 0.57(0.55,0.60) High trig 7.1 39.6 60.2 0.52(0.50,0.54) 8.0 92.6 42.2 67.4 0.52(0.51,0.54) 10.0 92.0 24.5 71.2 Childhood BMI was a weak predictor for adult hypertension and adverse lipid levels Similarly, the specificities for IOTF cut-offs were high (91.6-93.1%), and sensitivities were relatively low (7.1 to 14.6%).

Summary Prediction of adverse adult CVD risk factors from childhood BMI was modest: AUC≤0.75 (adult obesity), ≤0.68 (type 2 diabetes risk), ≤0.57 (hypertension or adverse lipid levels) Born in 1958, LOW child overweight/obesity prevalence by IOTF cut-offs, HIGH in adulthood. Prediction of adult obesity from IOTF cut-offs was low. Internal cut-offs for this population had higher sensitivities than IOTF cut-offs, but lower specificities. Low internal (study specific) cut-offs had limited utility for identification of children at high risk of adult CVD outcomes (identified a large proportion of children, differed across adult outcome).

Summary Prediction of adult CVD risk factors from childhood overweight/obesity was modest in a population experiencing rapid change in obesity prevalence over their lifetime. Neither IOTF nor our population-specific cut-offs for childhood BMI provided adequate diagnostic tools for adult CVD risk factors in a population experiencing such a rapid change

Life-course BMI trajectories 1946 and 1958 British birth cohorts Figures show the observed mean BMI (dots) and estimated BMI trajectories (solid lines) of the two cohorts. As expected the rate of BMI gain was faster in childhood than in adulthood. The were linear trends in BMI in childhood in both cohorts and in adulthood in the 1958 cohort, but a curvilinear trend in adulthood in the 1946 females. Comparing these cohorts: For boys, BMI at age 7y and slope in childhood is similar but is steeper for adult BMI gain for the 1958 cohort. At age 45y the difference in mean BMI is 1.8 kg/m2. For girls, slower childhood rate in the 1958 cohort compared to the 1946 cohort. In adulthood, the 1946 cohort grew at a slower rate than the 1958 cohort in early adulthood but thereafter at a similar rate to that of the 1958 cohort. At 45y the difference in mean BMI was 1.2 kg/m2. If 1958 cohort followed their age trend, by age 53y mean BMI will reach 30 kg/m2 (men) and 29 kg/m2 (females) *Li et al. Am J of Epidemiol (2009)

Association between BMI and adult SBP (males) 1946 and 1958 British birth cohorts

Life-course BMI trajectories 1946 and 1958 British birth cohorts Correlation (r) 1946 1958 Child slope 0.12 0.20 Adult slope 0.18 0.32 Figures show the observed mean BMI (dots) and estimated BMI trajectories (solid lines) of the two cohorts. As expected the rate of BMI gain was faster in childhood than in adulthood. The were linear trends in BMI in childhood in both cohorts and in adulthood in the 1958 cohort, but a curvilinear trend in adulthood in the 1946 females. Comparing these cohorts: For boys, BMI at age 7y and slope in childhood is similar but is steeper for adult BMI gain for the 1958 cohort. At age 45y the difference in mean BMI is 1.8 kg/m2. For girls, slower childhood rate in the 1958 cohort compared to the 1946 cohort. In adulthood, the 1946 cohort grew at a slower rate than the 1958 cohort in early adulthood but thereafter at a similar rate to that of the 1958 cohort. At 45y the difference in mean BMI was 1.2 kg/m2. If 1958 cohort followed their age trend, by age 53y mean BMI will reach 30 kg/m2 (men) and 29 kg/m2 (females) *Li et al. Am J of Epidemiol (2009)

Acknowledgements Angela Pinot de Moira Chris power MRC has funded the 45y survey of the 1958 cohort Leah Li is funded as a Career Development Award in Biostatistics And to our funders ..

Prediction of adult CVD risk factors from child BMI   IOTF cut-offs Study (1958 cohort) specific cut-offs Sensitivity Specificity Cut-offs % AUC (95% CI) Obese 7 15.3 94.8 16.0 15.8 43.8 61.5 61.8 0.65(0.64,0.67) (BMI≥30) 11 19.5 95.8 17.0 17.9 40.5 66.1 67.7 0.72(0.71,0.73) 16 24.8 95.9 20.5 21.3 38.4 67.3 70.6 0.75(0.74,0.77) Abdominal 13.0 95.2 51.2 65.2 0.61(0.59,0.62) obesity 15.7 96.3 17.3 37.3 54.7 72.1 0.68(0.66,0.69) 19.0 96.1 21.0 41.0 59.2 68.5 0.69(0.68,0.71) Type 2 diabetes 15.9 92.8 16.2 17.6 23.9 41.9 76.6 0.59(0.54,0.63) 24.2 18.4 27.7 49.5 73.0 0.65(0.60,0.69) 31.5 92.0 20.4 23.1 29.4 60.2 71.6 0.68(0.63,0.72) Prediction improved with increasing childhood age. For all CVD risk factors BMI16 was best predictor for adult obesity. IOTF cut-offs: high specificities but VERY Low sensitivities for predicting adult CVD risk factors. Specificities for adult obesity (94.8-95.9%) - only a small proportion (4.1-5.2%) of non-obese adults were classified as overweight/obese as a child. For adult obesity (15.3-24.8%) - a substantial proportion of obese adults (75.2-84.7%) were classified as non-overweight as a child. Similarly, abdominally obese and high diabetes risk at 45y ------------------------------------------------------------------ Study-specific cut-offs for each adult risk factor provided lower specificities than IOTF cut-offs, but improved sensitivities For predicting adult obesity, specificity & sensitivity for optimal cut-offs ranged 61.8 to 70.6% and 61.5 to 67.3%. E.g. 29.4% non-obese adults identified as at-risk and 32.7% obese adults not identified using internal cut-offs for BMI16. By definition, internal cut-offs had a higher combination of sensitivity & specificity than IOTF (e.g. 137.9 v 120.7 for BMI16). Similar cut-off points were found for predicting abdominal obesity. For elevated risk of type 2 diabetes, specificities between 71.6 and 76.6% indicate that 23.4-28.4% adults with low diabetes risk were identified as above the BMI cut-off in childhood, while sensitivities from 41.9 to 60.2% indicate that 39.8-58.1% adults with high diabetes risks were not identified as above the BMI cut-offs in childhood. Internal cut-offs varied according to adult CVD risk factors, were lower than IOTF cut-offs, therefore identified larger proportions of the population in childhood as having increased risk of adult CVD outcomes (15.6-55.5% vs 6.3-10.5%). Individuals with a child BMI above internal cut-offs had increased adult CVD risks. E.g. 38.4% of individuals with a BMI16 above cut-offs (20.5 kg/m2 for boys; 21.3 kg/m2 for girls) had an increased risk for adult obesity: OR=5.0 (4.4, 5.6). For elevated risk of type 2 diabetes, 29.4% individuals whose BMI16 above cut-offs (20.4 and 23.1 kg/m2) had an increased diabetes risk: OR= 3.8 (2.8, 5.2). 

Prediction of adult CVD risk factors from child BMI   IOTF cut-offs Study (1958 cohort) specific cut-offs Sensitivity Specificity Cut-offs % AUC (95% CI) Hypertension 7 8.3 92.7 16.1 16.6 32.5 39.0 69.7 0.53(0.52,0.55) 11 10.6 93.1 16.5 17.7 46.9 55.7 56.1 0.54(0.52,0.55) 16 12.5 92.2 19.8 24.3 30.8 44.8 73.9 0.54(0.52, .55) High LDL 7.6 92.5 17.1 17.2 15.6 17.3 84.6 0.50(0.49,0.52) 8.2 92.4 20.5 25.0 31.6 76.6 0.51(0.49,0.53) 8.5 91.6 21.4 23.0 21.2 25.1 79.8 0.51(0.49,0.52) Low HDL 10.1 93.0 15.7 15.8 47.8 52.1 52.9 0.54(0.51,0.56) 11.8 16.2 18.2 46.6 54.9 54.2 0.57(0.55,0.59) 14.6 23.6 24.5 39.1 78.0 0.57(0.55,0.60) High trig 7.1 16.3 39.8 39.6 60.2 0.52(0.50,0.54) 8.0 92.6 18.3 35.4 42.2 67.4 0.52(0.51,0.54) 10.0 92.0 22.8 21.0 27.6 71.2 Childhood BMI was a weak predictor for adult hypertension and adverse lipid levels Similarly, the specificities for IOTF cut-offs were high (91.6 to 93.1%) for other CVD risk factors, such as hypertension and lipid levels, and sensitivities were relatively low (7.1 to 14.6%). ------------------------------------------------------------------ Study-specific cut-offs Internally derived childhood BMI cut-offs for each adult risk factor provided lower specificities than IOTF cut-offs, but improved sensitivities (Tab 2). For predicting adult obesity, specificity & sensitivity for optimal cut-offs ranged 61.8 to 70.6% and 61.5 to 67.3% (Tab 2). E.g. 29.4% non-obese adults identified as at-risk and 32.7% obese adults not identified using internal cut-offs for BMI16. By definition, internal cut-offs had a higher combination of sensitivity & specificity than IOTF (e.g. 137.9 v 120.7 for BMI16). Similar cut-off points were found for predicting abdominal obesity. For elevated risk of type 2 diabetes, specificities between 71.6 and 76.6% indicate that 23.4-28.4% adults with low diabetes risk were identified as above the BMI cut-off in childhood, while sensitivities from 41.9 to 60.2% indicate that 39.8-58.1% adults with high diabetes risks were not identified as above the BMI cut-offs in childhood (Tab 2). Internal cut-offs varied according to adult CVD risk factors, were lower than IOTF cut-offs, therefore identified larger proportions of the population in childhood as having increased risk of adult CVD outcomes (15.6-55.5% vs 6.3-10.5%). Individuals with a child BMI above internal cut-offs had increased adult CVD risks. E.g. 38.4% of individuals with a BMI16 above cut-offs (20.5 kg/m2 for boys; 21.3 kg/m2 for girls) had an increased risk for adult obesity: OR=5.0 (4.4, 5.6). For elevated risk of type 2 diabetes, 29.4% individuals whose BMI16 above cut-offs (20.4 and 23.1 kg/m2) had an increased diabetes risk: OR= 3.8 (2.8, 5.2). 

Prediction of adult CVD risk factors from changes of child BMI   Age Cut-offs for BMI gain (kg/m2) % at risk Sensitivity Specificity AUC (95% CI) Overwt/obese 7-11y 1.31 1.96 40.2 47.7 73.8 0.61 (0.60, 0.63) 11-16y 3.03 4.41 39.2 45.0 71.8 0.56 (0.54, 0.57) Obese 1.26 2.26 37.9 56.3 68.1 0.65 (0.64, 0.67) 4.10 4.56 24.5 36.9 79.5 0.59 (0.57, 0.61) Abdominal 1.64 1.51 41.7 56.0 65.9 0.64 (0.62, 0.65) Obesity 4.37 22.3 29.6 81.7 0.55 (0.54, 0.57) Type 2 diabetes or 1.33 2.60 33.8 59.6 67.0 0.64 (0.60, 0.69) HbA1c>=7% 3.24 5.22 30.2 49.3 70.4 0.60 (0.54, 0.65) Hypertension 0.65 1.69 54.3 63.7 48.8 0.53 (0.51, 0.54) 2.65 4.65 41.9 53.5 62.1 0.51 (0.49, 0.53) High LDL 1.74 3.10 24.3 30.9 77.3 (>4.13 mmol/l ) 2.96 4.42 44.9 60.9 0.49 (0.46, 0.51) Low HDL 2.66 2.34 22.7 34.2 79.2 0.57 (0.55, 0.59) (<1.0/1.3 mmol/l) 5.60 4.84 14.1 21.3 87.1) 0.52 (0.50, 0.55) High trig 1.57 2.30 32.6 37.5 69.4 0.50 (0.49, 0.52) (>2.3 mmol/l ) 1.68 3.77 61.2 73.7 43.8 0.49 (0.47, 0.51)

ROC curves of predicting obesity45 from BMI changes (7-11, 11-16y, males and females) BMI growth Large increases in BMI between childhood ages predicted adult obesity. The AUC was greater for BMI increases between 7-11y than 11-16y.