A person’s lifestyle as an adult, including their diet and exercise habits, and reproductive history, plays a more integral role in bone health than does his or her birth weight or other factors associated with early life, UK researchers suggest.

Data collected from hundreds of middle-aged individuals revealed that their adult lifestyle had more of an impact on their bone mineral density than did factors related to their early life, such as birth weight. Early lifestyle factors, on the other hand, appeared to influence bone size.

Previous research suggested that a person’s health during their middle age years is strongly influenced by their fetal development.

Researchers have associated poor growth during this stage, as well as in infancy, with less skeletal growth and bone mass and a greater risk of Osteoporosis and bone fracture.

“Previous studies have suggested a link between birth weight and bone health,” said study author Dr. Mark S. Pearce of the University of Newcastle upon Tyne. “In our study, we confirmed the association between smaller birth weight (adjusted for gestational age) and bone size, but not for bone mineral density.”

Instead, “the study suggests that adult factors are more important than early life events in determining bone density in middle age,” co-author Roger M. Francis told.

Among 389 adults who were followed from birth, larger birth weights predicted greater bone sizes for men, even after their adult height and weight was taken into consideration, researchers report in the Journal of Epidemiology and Community Health.

“Smaller babies are likely to have smaller skeletal size as adults,” Francis explained. “As small skeletal size is also a risk factor for fracture, these individuals may be at increased risk of fracture in later life.”

Early life, including birth weight, and other factors related to development as a fetus, infant or child, explained some of the variation in bone mineral density among men. Yet among women, early life factors accounted for much less of the variation in bone density. More significant among women, study findings show, was their adult weight.

In fact, for both men and women, adult weight accounted for nearly 25 percent of the variation in hip bone mineral density, the report indicates.

Further, other adult lifestyle factors also contributed to bone health among both sexes. For example, alcohol drinking was found to be associated with men’s bone size, and decreased intake of vitamin C was linked to decreased hip bone mineral density in men. In women, more pregnancies was associated with less dense bones in the hip area.

This study, Francis told, shows that “promotion of a healthier adult lifestyle is the public health intervention most likely to improve bone health in middle age.” In light of the findings, Francis advises that parents ensure that children get enough calcium and vitamin D “to optimize skeletal growth.” Adults, on the other hand, should be aware that “lifestyle factors such as avoiding smoking and excess alcohol consumption, (engaging in) regular physical activity and eating a balanced diet rich in calcium should help to maintain bone health, but are not guaranteed to prevent osteoporosis or fractures later in life.”

SOURCE: Journal of Epidemiology and Community Health, June 2005.