Is body mass index before middle age related to coronary heart disease risk in later life? Evidence from observational studies.

OBJECTIVE: Although obesity beginning early in life is becoming more common, its implications for coronary heart disease (CHD) risk in later life remain uncertain. We examined the relationship of body mass index (BMI) before 30 years of age to CHD risk in later life. DESIGN: Systematic review of published studies relating BMI between age 2 and 30 years to later CHD risk. Studies were identified using Medline (1950 onwards), Embase (1980 onwards) and Web of Science (1970 onwards) databases (to November 2007). MEASUREMENTS: Relative risks (RR) of CHD associated with a 1 standard deviation (s.d.) higher BMI (most based on a narrow age range at measurement) were extracted by two authors independently, and combined using random-effect models. RESULTS: A total of 15 studies provided 17 estimates (731 337 participants, 23 894 CHD events) of the association of early BMI to later CHD outcome. BMI in early childhood (2-6 years, 3 estimates) showed a weak inverse association with CHD risk (RR 0.94, 95% CI 0.82-1.07). BMI in later childhood (7 to <18 years, 7 estimates) and BMI in early adult life (18-30 years, 7 estimates) were both positively related to later CHD risk (RR 1.09, 95% CI 1.00-1.20; RR 1.19, 95% CI 1.11-1.29 respectively). However, there was considerable statistical heterogeneity between study estimates. Results were unaffected by adjustment for social class and/or cigarette smoking, blood pressure and/or total cholesterol, in studies with available data. Gender and year of birth (1900-1976) had little effect on the association. CONCLUSIONS: BMI is positively related to CHD risk from childhood onwards; the associations in young adults are consistent with those observed in middle age. Long-term control of BMI from childhood may be important to reduce the risk of CHD.

Early influences on adult lung function in two national British cohorts.

OBJECTIVES: To compare adult lung function in two national British cohorts, born in 1946 and 1958, in relation to birth weight, postnatal growth and early air-pollution exposure. DESIGN AND SETTING: Persons born in England, Scotland and Wales during 1 week in March 1946 and in 1958 and followed from childhood into adult life. MAIN OUTCOME MEASURES: Forced expiratory volume in 1 sec (FEV(1)) and forced vital capacity (FVC), measured at age 43 years on subjects born in 1946 (n = 2167) and age 44-45 years on subjects born in 1958 (n = 5947). Spirometric indices were adjusted for gender, adult standing height, smoking history and socioeconomic position in childhood, and analysed in relation to birth weight, growth pattern and area of birth, classified into four groups of differing exposure to domestic coal smoke pollution. RESULTS: Within each cohort, FEV(1) and FVC were positively associated with birth weight and proportional sitting height independent of adult height. Pooling results for both cohorts, the mutually adjusted increment in FEV(1) per 1SD increment was 30 ml (95% CI 16 to 45) for birth weight and 19 ml (95% CI 5 to 33) for proportional sitting height. The proportion of adult height attained by age 7 years and early air-pollution exposure were unrelated to adult lung function. CONCLUSIONS: A small but significant influence of birth weight and trunk size on lung function is confirmed, but neither differences in prenatal and postnatal growth nor differences in childhood air-pollution exposure are likely explanations of the differences in spirometric performance between British adults born in 1946 and 1958.