Coffee, tea and caffeine consumption in relation to osteoporotic fracture risk in a cohort of Swedish women

Introduction: Consumption of coffee and tea, and total intake of caffeine has been claimed to be associated with osteoporotic fracture risk. However, results of earlier studies lack consistency. Methods: We examined this relation in a cohort of 31,527 Swedish women aged 40-76 years at baseline in 1988. The consumption of coffee, caffeinated tea and the intake of caffeine were estimated from a self-administered food frequency questionnaire (FFQ). Multivariate-adjusted hazards ratios (HRs) of fractures with 95% confidence intervals (95% CIs) were estimated by Cox proportional hazards models. Results: During a mean follow-up of 10.3 years, we observed 3,279 cases with osteoporotic fractures. The highest (> 330 mg/day) compared with the lowest (< 200 mg/day) quintile of caffeine intake was associated with a modestly increased risk of fracture: HR 1.20 (95% CI: 1.07-1.35). A high coffee consumption significantly increased the risk of fracture (p for trend 0.002), whereas tea drinking was not associated with risk. The increased risk of fracture with both a high caffeine intake and coffee consumption was confined to women with a low calcium intake (< 700 mg/day): HR 1.33 (95% CI: 1.07-1.65) with >= 4 cups (600 ml)/day of coffee compared to < 1 cup (150 ml)/day. The same comparison but risk estimated for women with a high propensity for fractures (>= 2 fracture types) revealed a HR of 1.88 (95% CI: 1.17-3.00). Conclusions: In conclusion, our results indicate that a daily intake of 330 mg of caffeine, equivalent to 4 cups (600 ml) of coffee, or more may be associated with a modestly increased risk of osteoporotic fractures, especially in women with a low intake of calcium.