SEASONAL HEIGHT VELOCITY VARIATION IN BOYS AND GIRLS 8-18 YEARS

This study investigated the seasonal variation in height velocity duri ng the summer and winter months. The subjects were healthy children, 1 09 boys and 119 girls, 8.5-18.0 years of age who are part of an ongoin g longitudinal study of bone mineral accrual. Anthropometric dimension s were taken twice a year, in the fall in conjunction with the annual bone assessment measures and 6 months later. Six-month velocities for height were calculated, which produced 982 velocities in boys and 1043 velocities in girls. Over the age range studied, summer velocities ac counted for at least 67% of the total yearly growth in boys and 60% of the total yearly growth in girls. Separate two-way ANOVAs (season by age) were used to compare the summer and winter velocities over half-y early age increments in both sexes. Season and age effects were signif icant (P < 0.01), but the interaction effect was not significant. The seasonal differences converged in the later years when the summer and winter velocities decreased to zero. The results demonstrate the impor tance of considering seasonal variation in height velocity in designin g studies and in assessing and interpreting growth data. (C) 1997 Wile y-Liss, Inc.