Birth weight, infant growth, and adolescent blood pressure using twin status as an instrumental variable in a Chinese birth cohort: "Children of 1997".
OBJECTIVE
To evaluate the credibility of twin status as an instrumental variable for birth weight and infant growth and to obtain less-confounded estimates of the associations of birth weight or infant growth with adolescent blood pressure (BP).


METHODS
Prospective population-based "Children of 1997" birth cohort of all surviving infants born in Hong Kong, China, from April to May 1997 with sex-, age-, and height-specific BP z-score at approximately 11 years (n = 6276) and approximately 13 years (n = 5305).


RESULTS
In instrumental variable analyses, birth weight-for-gestational age z-score was not associated with z-score for systolic BP (0.01; 95% confidence interval [CI], -0.22 to 0.25) or diastolic BP (0.04; 95% CI, -0.09 to 0.18) at approximately 11 years adjusted for maternal age and migrant status (F = 38.6). Change in weight z-score at 0 to 12 months was not associated with z-score for systolic BP (-0.003; 95% CI, -0.15 to 0.15) or diastolic BP (-0.02; 95% CI, -0.10 to 0.07) at approximately 11 years (F = 54.4). Estimates were similar for BP at approximately 13 years, although the F-statistic was lower.


CONCLUSIONS
Birth weight and infant growth may make little contribution to adolescent BP. Extending consideration of the effects of early life to other growth periods, such as puberty, on BP might yield public health benefits.
School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Man Ki
MK
Kwok
School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Shiu Lun
SL
Au Yeung
School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Gabriel M
GM
Leung
School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China; City University of New York School of Public Health and Hunter College, New York, NY. Electronic address: cms1@hkucc.hku.hk.
C Mary
CM
Schooling
D000293:Adolescent; D041923:Adolescent Development / Q000502:physiology; D001724:Birth Weight / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D002648:Child; D002657:Child Development / Q000502:physiology*; D002675:Child, Preschool; D055812:Community-Based Participatory Research; D005260:Female; D006723:Hong Kong; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D008423:Maternal Age; D011446:Prospective Studies; D012959:Socioeconomic Factors; D014427:Twins
Birth weight; Blood pressure; Child; Cohort studies; Infant growth; Twins