Parents who are active during pregnancy and early in their child's life tend to raise more active children, finds a study published on bmj.

Some risk factors for adult diseases are associated with lower levels of physical activity in children. Associations have also been reported between early life factors (from birth to around five years) and childhood obesity.

But little is known about the early life influences on children's physical activity.

So researchers identified children aged 11 to 12 who were taking part in the Avon Longitudinal Study of Parents and Children (ALSPAC). Each child was asked to wear an accelerometer for seven days, which recorded minute by minute the intensity and frequency of physical activity.

Valid data, defined as at least three days of at least 10 hours per day, were collected from 5,451 children and were analysed against various factors hypothesised to affect physical activity.

Several factors showed a modest association with later physical activity. These included mother's activity during pregnancy (specifically brisk walking and swimming), season of birth, one or both parents' physical activity when the child was aged 21 months, and having an older sibling.

The authors explain that the link with mother's activity during pregnancy is unlikely to be due to biological factors inside the womb. Instead, mothers who are physically active during pregnancy are likely to keep active after pregnancy, and that this in turn influences children's physical activity.

The association with season of birth is difficult to explain, they add, but it may be linked to school starting age.

Smoking in the mother and her partner were both positively associated with physical activity. This is surprising, say the authors, because maternal smoking during pregnancy is associated with childhood obesity, but they suggest it may be a result of the social patterning of smoking behaviour.

Few of the pre-school exposures (2-5 years) were associated with later physical activity. There was a small association with TV viewing at 38 and 54 months, but this was modest.

We have shown that early life factors have limited influence on later physical activity in 11 to 12 year olds, but that children are slightly more active if their parents are active early in the child's life, say the authors.

Helping parents to increase their physical activity therefore may promote children's activity.

They recommend that future research should re-examine these associations in later adolescence when physical activity declines, particularly in girls.

Early life determinants of physical activity in 11 and 12 year olds: a cohort study BMJ Online First

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