Effects of creatine supplementation on children and adolescents
The effects of age during creatine supplementation has been a controversial topic ever since creatine was made available for public use.  Studies in this area have shifted there focus particularly on the effects of creatine supplementation in the elderly and children / adolescents.  With more research becoming available it has been demonstrated that children, adolescents, and elderly can all benefit from acute creatine use.  However, little is still known regarding the effects on these age groups due to chronic creatine use.

Creatine has not been proven by research to interfere with growth in children or adolescents.  However, the number of long term studies regarding creatine's effects on child and adolescent growth are limited.  Exercise Physiologist and Physicians advise creatine supplementation until full maturity is reached.  This is not due to negative health effects, but because performance can be greatly improved during childhood and adolescents just by participating in physical activities and introductory resistance training.  Less risky and inexpensive methods such as evaluating one's diet or the use of recovery mixes (protein) should  always be considered before an individual of any age decides to supplement creatine. If one chooses to supplement creatine wait until maturity is reached or when adaptations from training reach a plateau.

Creatine supplementation and high school athletes

Is There a Physiologic Basis for Creatine Use in Children and Adolescents

CNN Article
 

Effects of creatine supplementation on the elderly
Muscular PCr levels decrease beginning the fifth decade of life which may lead to gradual loss of strength causing fatigue later in life.  Creatine supplementation by the elderly has shown to decrease the loss of strength and improve functional capacity.  Research shows that creatine supplementation can improve short term, lower body, power oriented functional living task with no signs of renal or hepatic dysfunction's.  Elderly tend not to gain weight during creatine supplementation like younger people do because of an age related decline in the body's total creatine concentrations and the decrease in type II muscle fiber content.  However, more research is still needed to examine further benefits of creatine supplementation for the elderly.
Creatine Supplementation and Elderly Women
 

Effects of creatine supplementation on females
Research shows that women experience the same increases in physical performance due to creatine supplementation that men do.  Numerous studies show no negative effects for women that use this supplement.  Creatine has shown to alleviate bloating in women during menstruation due to water retention.  Although little has been studied regarding creatine supplementation during pregnancy it is strongly discouraged.

Recent studies have shown that the difference in exercise metabolism of females compared to males may hinder creatine's effectiveness.  Females conserve energy more efficiently, use more fats then carbohydrates for fuel, and use less protein compared to similarly trained males (Ferreira, 1999).