Importance of changes in body mass index from adolescence to middle age as a risk factor for osteoporosis: the Japan Nurses' Health Study.

OBJECTIVE

To investigate the association between changes in body mass index (BMI) from adolescence to middle age and osteoporosis risk among participants in the Japan Nurses' Health Study (JNHS), a nationwide prospective cohort study.

METHODS

Data were reviewed for 15,019 participants in the JNHS. After excluding 6,511 participants aged below 40 years or diagnosed with osteoporosis at baseline, 8,508 participants were included. The mean age at baseline was 47.5±5.4 years, and the mean follow-up period was 15.5±6.3 years. Low body weight (L) was defined as BMI <18.5 kg/m 2 , normal weight (N) as BMI ≥18.5 to <25 kg/m 2 , and overweight (O) as BMI ≥25 kg/m 2 .

RESULTS

Age-adjusted hazard ratios for new-onset osteoporosis according to change in BMI from age 18 years to baseline compared with N to N were L to L, 1.65 (95% CI: 1.10-2.47), N to L, 1.44 (1.08-1.91) and N to O, 0.65 (0.54-0.79). Multivariable-adjusted hazard ratios for osteoporosis compared with N to N were L to L, 1.51 (0.98-2.33), N to L, 1.29 (0.95-1.76) and N to O, 0.68 (0.55-0.82). Regarding age at diagnosis of osteoporosis compared with N to N, the HR for L to L was 1.97 (1.04-3.72) for participants in their 50s, and the HR for N to O was 0.56 (0.42-0.76) for participants in their 60s.

CONCLUSIONS

Persistent underweight status in women from adolescence to middle age is a risk factor for developing earlier osteoporosis in menopause.