Stroke: oral contraceptive pill increases the risk

Clinical bottom line (level 3a)

  1. Women on the oral contraceptive pill compared with control are a slightly increased risk of having a stroke.
Gillum et al: Journal of the American Medical Association 2000; 284 : 72-78
Expires November 2003

The study

Systematic review of all cohort or case-control studies of
  • Patients: women
  • Intervention: on oral contraceptive pill
  • Outcome: stroke

    Articles found in all languages using Medline, BIOSIS, Dissertation AbstractsOnline, Index Medicus, January 1960 to November 1999 (search terms: oral contraceptives (side effects, complications), stroke, estrogen, cerebral, ischemia, thrombosis, venous sinus ) and searching bibliographies of review articles, pertinent original articles and textbooks. In addition experts in the field were contacted.

    Selection criteria: by 2 independent reviewers: see above and below
    Appraisal criteria: by 2 independent reviewers: based on study design including confounding factors
    Articles excluded if:
    • fewer than 10 strokes reported
    • no clear differentiation between ischaemic or haemorrhage stroke
    • insufficient data to calculate odds ratios
    • duplicate study
    • age not adjusted for in study design


    16 studies found
    Studies were found to be significantly heterogeneous - size of the risk depended on study design (cohort v. case-control), the confounding factors used, and the dose of estrogen.

    The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)    		 NNF
    (95% CI)
    stroke 12 months / %
    (% to %)
    ( to )

    prognostic factor for
    stroke     		time to outcome adjusted RR
    (95% CI)    		 NNF+
    (95% CI)
    oral contraceptive pill ? 2.75
    (2.24 to 3.38)     		24000
    ( to )

    Comments

    1. A funnel-plot suggested no evidence of publication bias.

    Citation

    1. Gillum LA, Mamidipudi SK, Johnston SC: ischemic stroke risk with oral contraceptives: a meta-analysis. Journal of the American Medical Association 2000; 284 : 72-78
    Search Terms: from ACP Journal Club
    Contributor: Chris Ball, November 2001
    Reviewer:

    Clinical Question.
    Patient
    Intervention or Exposure
    Outcome