Body mass index in adults with intellectual disability: distribution, associations and service implications: a population-based prevalence study

Background Previous studies of weight problems in adults with intellectual disability (ID) have generally been small or selective and given conflicting results. The objectives of our large-scale study were to identify inequalities in weight problems between adults with ID and the general adult population, and to investigate factors associated with obesity and underweight within the ID population. Methods We undertook a population-based prevalence study of 1119 adults with ID aged 20 and over on the Leicestershire Learning Disability Register who participated in a programme of universal health checks and home interviews with their carers. We performed a cross-sectional analysis of the register data and compared the observed and expected prevalences of body mass index categories in the ID and general populations using indirect standardisation for age. We used logistic regression to evaluate the association of a range of probable demographic, physical, mental and skills attributes with obesity and underweight. Results In those aged 25 and over, the standardised morbidity ratio (SMR) for obesity was 0.80 (95% CI 0.64-1.00) in men and 1.48 (95% CI 1.23-1.77) in women. The SMR for underweight was 8.44 (95% CI 6.52-10.82) in men and 2.35 (95% CI 1.72-3.19) in women. Among those aged 20 and over, crude prevalences were 20.7% for obesity, 28.0% for overweight, 32.7% for normal weight and 18.6% for underweight. Obesity was associated with living independently/with family, ability to feed/drink unaided, being female, hypertension, Down syndrome and the absence of cerebral palsy. Underweight was associated with younger age, absence of Down syndrome and not taking medication. Conclusion Obesity in women and underweight in both men and women was more common in adults with ID than in the general population after controlling for differences in the age distributions between the two populations. The associated factors suggest opportunities for targeting high-risk groups within the ID population for lifestyle and behaviour modification.