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

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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

Imperial College, 16 Nov 2011

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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?

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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)

† Kuczmarski et al CDC growth charts 2001‡ Cole et al 2000

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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)

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CVD risk factors at 45y in 1958 cohort

Males FemalesOverweight 49.7 % 32.7 %Obese 25.2 % 23.5 %

Abdominal obesity 32.7 % 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 %

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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@16 23.9(6.3) 24.4(9.3)Obese@16 28.9(1.4) 29.4(1.2)


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Childhood BMI






At 7-16y, 6.3-10.5% classified as overweight or obese

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Childhood BMI






At 7-16y, 6.3-10.5% classified as overweight or obese

HSE06-08: 21% boys, 24% girls (9-11y) were overweight or obese

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Childhood BMI






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.

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ROC curves of predicting obesity 45 from child BMI(Males & females)

ROC analysis (AUC) to assess how well BMI at each age predicts adult obesity

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ROC curves of predicting obesity 45 from child BMI(Males & females)

ROC analysis (AUC) to assess how well BMI at each age predicts adult obesity

AUC increase with ageBMI16 was best predictor for adult obesity.Greater increase in AUC (7-11). Than (11-16)

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Prediction of adult CVD risk factors from child BMI

IOTF cut-offsSensitivity Specificity

Obese 7 15.3 94.8

(BMI≥30) 11 19.5 95.8

16 24.8 95.9

Abdominal 7 13.0 95.2

obesity 11 15.7 96.3

16 19.0 96.1

Type 2 7 15.9 92.8

diabetes 11 24.2 92.8

16 31.5 92.0

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IOTF cut-offsSensitivity Specificity

Obese 7 15.3 94.8

(BMI≥30) 11 19.5 95.8

16 24.8 95.9


obesity 11 15.7 96.3

16 19.0 96.1

Type 2 7 15.9 92.8

diabetes 11 24.2 92.8

16 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

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IOTF cut-offs

Sensitivity Specificity

Hypertension 7 8.3 92.7

11 10.6 93.1

16 12.5 92.2

High LDL 7 7.6 92.5

11 8.2 92.4

16 8.5 91.6

Low HDL 7 10.1 93.0

11 11.8 93.1

16 14.6 92.4

High trig 7 7.1 92.4

11 8.0 92.6 16 10.0 92.0

Childhood BMI was a weak predictor for adult hypertension, adverse lipids

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Internal cut-offs for child BMI for predicting adult CVD risk factors

Internal cut-offs (%)

BMI @7 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%)

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Internal cut-offs for child BMI for predicting adult CVD risk factors

Internal cut-offs (%)

BMI @7 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

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Childhood BMI cut-offs for predicting adult CVD risk factors

IOTF cut-offs (%) Internal cut-offs (%)Males Females

Childhood BMIOverweight@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)

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Study specific cut-offs


Obese 7 61.5 61.8

(BMI≥30) 11 66.1 67.7

16 67.3 70.6


obesity 11 54.7 72.1

16 59.2 68.5

Type 2 7 41.9 76.6

diabetes 11 49.5 73.0

16 60.2 71.6

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Study specific cut-offs


Obese 7 61.5 61.8

(BMI≥30) 11 66.1 67.7

16 67.3 70.6


obesity 11 54.7 72.1

16 59.2 68.5

Type 2 7 41.9 76.6

diabetes 11 49.5 73.0

16 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.

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Study specific cut-offsSensitivity Specificity


11 55.7 56.1

16 44.8 73.9

High LDL 7 17.3 84.6

11 31.6 76.6

16 25.1 79.8

Low HDL 7 52.1 52.9

11 54.9 54.2

16 39.1 78.0

High trig 7 39.6 60.2

11 42.2 67.4

16 24.5 71.2

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Study specific cut-offsSensitivity Specificity


11 55.7 56.1

16 44.8 73.9

High LDL 7 17.3 84.6

11 31.6 76.6

16 25.1 79.8

Low HDL 7 52.1 52.9

11 54.9 54.2

16 39.1 78.0

High trig 7 39.6 60.2

11 42.2 67.4 16 24.5 71.2

Childhood BMI - weak predictor for adult hypertension and adverse lipids

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IOTF cut-offs Study specific cut-offs Sensitivity Specificity 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 7 13.0 95.2 51.2 65.2 0.61(0.59,0.62)

obesity 11 15.7 96.3 54.7 72.1 0.68(0.66,0.69)

16 19.0 96.1 59.2 68.5 0.69(0.68,0.71)

Type 2 7 15.9 92.8 41.9 76.6 0.59(0.54,0.63)

diabetes 11 24.2 92.8 49.5 73.0 0.65(0.60,0.69)

16 31.5 92.0 60.2 71.6 0.68(0.63,0.72)

Li et al. Am J Clin Nutri (2011)

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IOTF cut-offs Study specific cut-offsSensitivity Specificity 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 7.6 92.5 17.3 84.6 0.50(0.49,0.52)

11 8.2 92.4 31.6 76.6 0.51(0.49,0.53)

16 8.5 91.6 25.1 79.8 0.51(0.49,0.52)

Low HDL 7 10.1 93.0 52.1 52.9 0.54(0.51,0.56)

11 11.8 93.1 54.9 54.2 0.57(0.55,0.59)

16 14.6 92.4 39.1 78.0 0.57(0.55,0.60)

High trig 7 7.1 92.4 39.6 60.2 0.52(0.50,0.54)

11 8.0 92.6 42.2 67.4 0.52(0.51,0.54)

16 10.0 92.0 24.5 71.2 0.50(0.49,0.52)

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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).

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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

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Life-course BMI trajectories 1946 and 1958 British birth cohorts

Males

15

17

19

21

23

25

27

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5 10 15 20 25 30 35 40 45 50 55

me

an

BM

I

46cohort

58cohort 1.8kg/m2

*Li et al. Am J of Epidemiol (2009)

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

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Life-course BMI trajectories 1946 and 1958 British birth cohorts

Males

15

17

19

21

23

25

27

29

5 10 15 20 25 30 35 40 45 50 55

me

an

BM

I

46cohort

58cohort 1.8kg/m2

*Li et al. Am J of Epidemiol (2009)

Correlation (r)

1946 1958

Child slope 0.12 0.20

Adult slope 0.18 0.32

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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

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IOTF cut-offs Study (1958 cohort) specific cut-offs

Sensitivity Specificity Cut-offs % Sensitivity Specificity 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 7 13.0 95.2 16.0 16.0 40.5 51.2 65.2 0.61(0.59,0.62)

obesity 11 15.7 96.3 17.3 17.9 37.3 54.7 72.1 0.68(0.66,0.69)

16 19.0 96.1 20.5 21.0 41.0 59.2 68.5 0.69(0.68,0.71)

Type 2

diabetes 7 15.9 92.8 16.2 17.6 23.9 41.9 76.6 0.59(0.54,0.63)

11 24.2 92.8 17.9 18.4 27.7 49.5 73.0 0.65(0.60,0.69)

16 31.5 92.0 20.4 23.1 29.4 60.2 71.6 0.68(0.63,0.72)

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IOTF cut-offs Study (1958 cohort) specific cut-offs

Sensitivity Specificity Cut-offs % Sensitivity Specificity 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 7.6 92.5 17.1 17.2 15.6 17.3 84.6 0.50(0.49,0.52)

11 8.2 92.4 17.2 20.5 25.0 31.6 76.6 0.51(0.49,0.53)

16 8.5 91.6 21.4 23.0 21.2 25.1 79.8 0.51(0.49,0.52)

Low HDL 7 10.1 93.0 15.7 15.8 47.8 52.1 52.9 0.54(0.51,0.56)

11 11.8 93.1 16.2 18.2 46.6 54.9 54.2 0.57(0.55,0.59)

16 14.6 92.4 23.6 21.2 24.5 39.1 78.0 0.57(0.55,0.60)

High trig 7 7.1 92.4 16.3 15.8 39.8 39.6 60.2 0.52(0.50,0.54)

11 8.0 92.6 17.1 18.3 35.4 42.2 67.4 0.52(0.51,0.54)

16 10.0 92.0 22.8 21.0 27.6 24.5 71.2 0.50(0.49,0.52)

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Prediction of adult CVD risk factors from changes of child BMI

AgeCut-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 7-11y 1.26 2.26 37.9 56.3 68.1 0.65 (0.64, 0.67)

11-16y 4.10 4.56 24.5 36.9 79.5 0.59 (0.57, 0.61)

Abdominal 7-11y 1.64 1.51 41.7 56.0 65.9 0.64 (0.62, 0.65)

Obesity 11-16y 4.37 4.56 22.3 29.6 81.7 0.55 (0.54, 0.57)

Type 2 diabetes or 7-11y 1.33 2.60 33.8 59.6 67.0 0.64 (0.60, 0.69)

HbA1c>=7% 11-16y 3.24 5.22 30.2 49.3 70.4 0.60 (0.54, 0.65)

Hypertension 7-11y 0.65 1.69 54.3 63.7 48.8 0.53 (0.51, 0.54)

11-16y 2.65 4.65 41.9 53.5 62.1 0.51 (0.49, 0.53)

High LDL 7-11y 1.74 3.10 24.3 30.9 77.3 0.51 (0.49, 0.53)

(>4.13 mmol/l ) 11-16y 2.96 4.42 40.2 44.9 60.9 0.49 (0.46, 0.51)

Low HDL 7-11y 2.66 2.34 22.7 34.2 79.2 0.57 (0.55, 0.59)

(<1.0/1.3 mmol/l) 11-16y 5.60 4.84 14.1 21.3 87.1) 0.52 (0.50, 0.55)

High trig 7-11y 1.57 2.30 32.6 37.5 69.4 0.50 (0.49, 0.52)

(>2.3 mmol/l ) 11-16y 1.68 3.77 61.2 73.7 43.8 0.49 (0.47, 0.51)

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ROC curves of predicting obesity45 from BMI changes (7-11, 11-16y, males and females)

Documents

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