title: Coffee, tea and caffeine consumption in relation to osteoporotic fracture risk in a cohort of Swedish women.
abstract: BACKGROUND
  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 > or =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 (> or =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.
authors.affiliation: Department of Toxicology, National Food Administration, P. O. Box 622, 75126 Uppsala, Sweden. heha@slv.se
authors.forename: H
authors.initials: H
authors.lastname: Hallström
authors.forename: A
authors.initials: A
authors.lastname: Wolk
authors.forename: A
authors.initials: A
authors.lastname: Glynn
authors.forename: K
authors.initials: K
authors.lastname: Michaëlsson
mesh_terms: D000328:Adult; D000368:Aged; D002110:Caffeine / Q000009:adverse effects*; D002118:Calcium / Q000378:metabolism; D002136:Calcium, Dietary / Q000008:administration & dosage; D003069:Coffee / Q000009:adverse effects*; D015331:Cohort Studies; D005260:Female; D006620:Hip Fractures / Q000209:etiology*; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000209:etiology*; D011446:Prospective Studies; D012306:Risk; D013662:Tea / Q000009:adverse effects*
chemical_list: D002136:Calcium, Dietary; D003069:Coffee; D013662:Tea; D002110:Caffeine; D002118:Calcium