1. 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

2. (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.

3. 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

4. Study sample British Birth Cohort - born in Great Britain in one week, Mar (≈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)

5. 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.

6. Childhood BMI IOTF cut-offs (%) Males Females Overweight@7 18.2(5.5)
18.0(7.2)
21.1(0.8)
21.0(1.6)
20.9(6.0)
21.2(7.9)
25.6(0.8)
26.1(1.1)
23.9(6.3)
24.4(9.3)
28.9(1.4)
29.4(1.2)
25.0(49.7)
25.0(32.7)
30.0(25.2)
30.0(23.5)
Based on the IOTF cut-offs, % 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)
21.1(0.8)
21.0(1.6)
20.9(6.0)
21.2(7.9)
25.6(0.8)
26.1(1.1)
23.9(6.3)
24.4(9.3)
28.9(1.4)
29.4(1.2)
25.0(49.7)
25.0(32.7)
30.0(25.2)
30.0(23.5)
At 7-16y, % classified as overweight or obese
Based on the IOTF cut-offs, % 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

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

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

10. 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

11. 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

12. 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

13. 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 % 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

14. 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 ( %), and sensitivities were relatively low (7.1 to 14.6%).

15. Internal cut-offs for child BMI for predicting adult CVD risk factors
( %)
( %)
( %)

16. Internal cut-offs for child BMI for predicting adult CVD risk factors
( %)
( %)
( %)
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

17. Childhood BMI cut-offs for predicting adult CVD risk factors
IOTF cut-offs (%)
Internal cut-offs (%)
Males
Females
Childhood BMI
18.2(5.5)
18.0(7.2)
( %)
21.1(0.8)
21.0(1.6)
20.9(6.0)
21.2(7.9)
( %)
25.6(0.8)
26.1(1.1)
23.9(6.3)
24.4(9.3)
( %)
28.9(1.4)
29.4(1.2)
Based on the IOTF cut-offs, % 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.

18. 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. 

19. 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: % adults with low diabetes risk identified as above BMI cut-offs in childhood, while % 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. 

20. 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

21. 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

22. 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 ( %) indicate - only % of non-obese adults were classified as overweight/obese as a child.
A substantial proportion of obese adults ( %) 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 % and %.
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 v for BMI16).
Similar cut-off points were found for predicting abdominal obesity.
For diabetes, specificities % indicate % 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 % 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 ( % vs %).
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)

23. 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 ( %), and sensitivities were relatively low (7.1 to 14.6%).

24. 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).

25. 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

26. 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)

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

28. 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)

29. 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 ..

30. 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 ( %) - only a small proportion ( %) of non-obese adults were classified as overweight/obese as a child.
For adult obesity ( %) - a substantial proportion of obese adults ( %) 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 v 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 % 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 % 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 ( % vs %). 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). 

31. 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 v 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 % 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 % 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 ( % vs %). 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). 

32. 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)

33. 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.