Body size in early life and risk of diabetes in adulthood

Thesis

Larger body size in adulthood increases the risk of diabetes in adulthood, whereas, paradoxically, being small at birth is associated with an increased risk of adult-onset diabetes. Direct comparisons of diabetes risks for different trajectories or combinations of body size at birth, childhood, early adulthood and late adulthood will help to better understand the complex relationships between body size throughout life and risk of adult-onset diabetes.

This thesis investigates the effects of early- versus late-life body size on risks of developing diabetes in adulthood among 413,516 women from the Million Women Study, with more than 24,000 diabetes cases identified through electronic linkage to routinely-collected national hospital admissions records. At the beginning of follow-up (mean age 60 [SD 5] years), women reported their birthweight, body size at ages 10 and 20 and current body mass index (BMI), which were validated against values recorded around respective ages. Cox proportional hazards regressions yielded multivariable-adjusted relative risks for adult-onset diabetes by different combinations of these four body size indices.

Within every body size category at younger ages, higher adult BMI sharply increased risks of adult-onset diabetes. The association between low birthweight and higher risks of diabetes was clear, independent and persistent among women with different combinations of body sizes at age 10, 20, and 60 years. Larger body size at ages 10 and 20 years was largely relevant to adult-onset diabetes risk as a predictor of adult adiposity. At every level of birthweight and adult BMI, there were additional risks of diabetes associated with being comparatively thin at age 10 years. However, after allowing for birthweight, size at age 10, and adult BMI, being small at age 20 years had a little additional effect on adult-onset diabetes risk.

In conclusion, as well as the known increased risk with adult adiposity, being small at birth and thin in childhood independently and persistently increase diabetes risk in adulthood.

Authors: Shawon, MSR

• DOI: 10.5287/ora-yqkqx5v0j
• Type of award: DPhil
• Awarding institution: University of Oxford
• Keywords: adult diabetes