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. Author manuscript; available in PMC: 2011 Jan 1.
Published in final edited form as: Ann Epidemiol. 2010 Jan;20(1):82–85. doi: 10.1016/j.annepidem.2009.09.001

TABLE 1.

Hazard ratios and 95% confidence intervals of breast cancer risk according to quartiles of serum calcium.

Total
subjects		 No. of
cases		 Person
years* 		Incidence
per 100,000		 HR (95% CI)† HR (95% CI)‡
All subjects (N=2,338)
 Total serum calcium (mmol/L)
  1.40-2.38 687 39 9,819 397 1 1
  2.39-2.44 605 27 8,699 310 0.76 (0.47, 1.26) 0.70 (0.42, 1.17)
  2.45-2.52 508 26 7,297 356 0.83 (0.50, 1.37) 0.84 (0.51-1.40)
  2.53-3.16 538 32 7,637 419 1.00 (0.62, 1.60) 0.98 (0.60, 1.60)
Ptrend = 0.99 Ptrend = 0.96
 Ionized calcium (mmol/L)
  0.94-1.21 666 39 9,148 426 1 1
  1.22-1.23 535 25 7,713 324 0.75 (0.45, 1.24) 0.83 (0.50, 1.40)
  1.24-1.25 482 27 7,050 383 0.89 (0.54, 1.47) 0.98 (0.59, 1.63)
  1.26-1.66 655 33 9,539 346 0.77 (0.48, 1.23) 0.85 (0.53, 1.38)
Ptrend = 0.37 Ptrend = 0.64
Postmenopausal women only (N=1,995)
BMI ≤ 27.4 kg/m2 (N=992)
 Total calcium (mmol/L)
  1.40-2.38 279 12 3,907 307 1 1
  2.39-2.44 264 11 3,708 297 0.87 (0.38, 1.98) 0.69 (0.28, 1.67)
  2.45-2.52 224 11 3,204 343 1.07 (0.46, 2.49) 0.88 (0.36, 2.19)
  2.53-3.16 225 10 3,139 319 1.13 (0.48, 2.67) 0.97 (0.39, 2.43)
Ptrend = 0.69 Ptrend = 0.93
 Ionized calcium (mmol/L)
  0.94-1.21 238 15 3,091 485 1 1
  1.22-1.23 227 8 3,233 247 0.50 (0.21, 1.21) 0.60 (0.24, 1.51)
  1.24-1.25 208 9 3,009 299 0.69 (0.29, 1.62) 0.78 (0.32, 1.92)
  1.26-1.66 319 12 4,627 259 0.54 (0.25, 1.18) 0.63 (0.27, 1.44)
Ptrend = 0.20 Ptrend = 0.37
BMI > 27.4 kg/m2 (N=985)
 Total calcium (mmol/L)
  1.40-2.38 252 16 3,414 469 1 1
  2.39-2.44 259 10 3,641 275 0.61 (0.26, 1.40) 0.56 (0.24, 1.35)
  2.45-2.52 215 13 2,973 437 0.89 (0.42, 1.91) 1.03 (0.46, 2.34)
  2.53-3.16 259 17 3,663 464 0.90 (0.45, 1.81) 0.94 (0.44, 1.98)
Ptrend = 0.97 Ptrend = 0.79
 Ionized calcium (mmol/L)
  0.94-1.21 287 14 4,070 344 1 1
  1.22-1.23 217 13 3,192 407 1.40 (0.64, 3.07) 1.52 (0.66, 3.51)
  1.24-1.25 180 12 2,701 444 1.41 (0.64, 3.11) 1.89 (0.80, 4.45)
  1.26-1.66 245 17 3,728 456 1.26 (0.61, 2.59) 1.59 (0.73, 3.47)
Ptrend = 0.55 Ptrend = 0.22

HR = hazard ratio; CI = confidence interval.

*

Total person years for cases and noncases.

†

Models are adjusted for age.

‡

Models are adjusted for age, menopausal status, age at menarche, age at menopause, parity, age at first birth, alcohol consumption, BMI, education, and postmenopausal hormone use.