Predicting adult metabolic syndrome from childhood body mass index: follow-up of the New Delhi birth cohort

Abstract

Objectives: To assess whether serial measurements of childhood body mass index (BMI) give clinically useful predictions of the risk of developing adult metabolic syndrome and impaired glucose tolerance or type 2 diabetes.

Design/setting: Follow-up of a community-based birth cohort in Delhi, India.

Participants: 1492 men and women aged 26-32 years whose BMI was recorded 6-monthly throughout childhood.

Main outcome measures: The predictive value of childhood BMI for adult metabolic syndrome and impaired glucose tolerance (IGT) and diabetes mellitus.

Results: 25% of subjects had metabolic syndrome and 15% had IGT/diabetes mellitus. Both outcomes were associated with greater childhood BMI gain (metabolic syndrome: OR 1.63 (95% CI 1.44 to 1.85); IGT/diabetes mellitus: 1.39 (1.20 to 1.60) per unit increase in within-cohort BMI SD score between 5 and 14 years). The best predictions of adult disease were obtained using a combined test comprising (i) any increase in BMI SD score between 5 and 14 years and (ii) a BMI SD score >0 at 14 years (metabolic syndrome: sensitivity 45%, specificity 78%; IGT/diabetes mellitus: 37%, 73%). Likelihood ratios were low (metabolic syndrome: 1.4-2.0; IGT/diabetes mellitus: 1.2-1.4). A single high BMI measurement at 14 years (overweight or obese, according to International Obesity Task Force criteria) was highly specific but insensitive (metabolic syndrome: sensitivity 7%, specificity 97%; IGT/diabetes mellitus: 8%, 97%). Charts for plotting BMI SD scores through childhood were produced.

Conclusions: Serial measurements of childhood BMI give useful predictions of adult risk and could guide advice to children and parents on preventing later disease.

Figure 1. Prevalence (%) of (a) metabolic syndrome and (b) IGT/diabetes according to absolute BMI SD-score and changes in BMI SD-score during childhood

The contour lines show the prevalence (%) of metabolic syndrome (upper panel) or IGT/diabetes (lower panel) for different combinations of change in BMI SD-score between two ages (x-axis) and BMI SD-score at the later age (y axis). They are drawn so that they cover the most ‘central’ 95% of the observed data points, in order to exclude areas where there were few observations. Perfectly vertical contour lines would indicate that the prevalence varies mainly with change in BMI SD-score, rather than with absolute attained BMI SD-score; horizontal contours indicate the opposite, and diagonal contours indicate that prevalence varies with both these parameters.

Figure 2. Chart for plotting BMI at different ages during childhood and converting BMI values into SD-scores (based on within-cohort data)

Measured BMI is plotted on the appropriate wavy line, at the child’s age. The SD-score can be read off the y-axis at the same horizontal level. This procedure is repeated at later ages. ‘Test-positive’ is defined as any increase in SD-score between measurements and an SD-score above the median at the later measurement. The right-hand chart shows the BMI trajectory of 3 cohort children; children A is ‘test positive’ at ages 5-8 and 8-11; child B is ‘test positive’ at ages 5-8 and 11-14 and child C is ‘test-negative’ at all ages.