Weight at Birth and Infancy in Relation to Adult Leukocyte Count: A Population-Based Study of 5619 Men and Women Followed from the Fetal Period to Adulthood

Context: Impaired fetal growth is associated with increased risk for coronary heart disease and diabetes in adulthood, but the underlying mechanism is unclear. Objective: The objective of the study was to examine the relation between early growth (weight at birth and first year) and adult total leukocyte count, the primary cell effectors of inflammation. Design: This was a birth cohort study (Northern Finland Birth Cohort 1966) with participants prospectively and longitudinally followed up from birth to age 31 yr. Setting: This was a general population-based cohort in Finland. Participants: A total of 5619 offspring of expectant mothers who attended a clinical examination and blood draw at 31-yr follow-up (4486 with complete data on weight at 1 yr) participated in the study. Main Exposure Variables: Weight at birth and at 1 year. Main Outcome Measure: Absolute leukocyte count was measured. Results: Total leukocyte count was lower at higher birth weight categories with or without adjustments for adult systolic blood pressure, total cholesterol, fasting insulin, body mass index, cigarette smoking, sex, gestational age, and other life course factors. The covariate-adjusted regression coefficient for log-transformed total leukocyte count (x 10(9) cells/liter) per 1 SD (525 g) increase in birth weight was -0.012(95% confidence interval -0.021 to -0.004). The association persisted, even when limiting our analyses among healthy and nonsmoking individuals, and the inversely linear relation was steepest among those with lower weight attained at 1 yr (P for interaction = 0.027). Conclusion: Poorer growth in early life was associated with systemic low-grade inflammation in adulthood. This relation suggests a plausible inflammatory mechanism linking early growth impairment with risk of coronary heart disease and diabetes later in life. (J Clin Endocrinol Metab 94: 1916-1922, 2009)