Long-term association between body size in adolescence or early adulthood and future fracture risk

Body size is known to influence bone mass and fracture risk throughout life; however, the critical period at which body size most strongly affects later fracture risk remains unclear. Herein, we investigated whether body size in adolescence or early adulthood is more strongly associated with future fracture risk, hypothesizing a stronger association for adolescence.

Participants included health examination attendees in the Okazaki region of the Japan Multi-Institutional Collaborative Cohort Study aged 35-79 years. Overall, 2152 males (mean age 58.5 ± 10.9 years) and 1900 females (54.9 ± 10.2 years) were analyzed. In the primary survey (2007-2011), participants recalled body size in junior high school and their 20 s. In the secondary survey, conducted approximately 5 years later, participants self-reported fracture history in the past year. Associations between recalled body size and fracture risk were examined using logistic regression.

Females with a thin body size in junior high school had a higher fracture risk than those with a normal body size (OR 2.29; 95% CI 1.10-4.76). However, a thin body size in the 20 s showed no association (OR 0.83; 95% CI 0.33-2.06). Additionally, no significant associations were observed for overweight females or males in either period.

In females, a thin body size in adolescence may be more strongly associated with future fractures than in early adulthood. Our findings provide a basis for future research confirming these associations with objective measures and longer follow-up.