La Vecchia 1999.

Methods	Case‐control study of hip fractures conducted at Ospedale Maggiore (included 4 largest teaching and general hospitals in Milan, Italy) between 1983 and 1992
Participants	Participants from control group within case‐control studies of breast and genital cancers (earlier reports: La Vecchia 1991; Parazzini 1996)
Interventions	Oral contraceptive use
Outcomes	Hip fracture Insufficient data for analysis; results presented as reported
Notes	Report was in a letter to journal editor. Earlier publications (cited in letter) provided study design information but time periods differed and analysis may have differed.
Risk of bias
Bias	Authors' judgement	Support for judgement
Case definition and representativeness	Low risk	Cases: 279 women, 29 to 74 years old, admitted for fracture of hip or proximal femur; median age 62 years
Exposed cohort: representativeness	Unclear risk	Not applicable
Control selection and definition; non‐exposed cohort selection	Low risk	Controls: 1861 women, 25 to 74 years old, admitted for acute condition (other than trauma) to same network of hospitals as cases; median age 55 years
Exposure ascertainment, including same method for cases and controls	Low risk	History of lifetime use of oral contraceptives (structured questionnaire); analyzed as 'ever use' and use for 2 years or longer. Ever use of OCs: cases (N = 10); controls (N = 167) Data collected for cancer studies as noted in 'Participants.'
Outcome assessment (cohort study): method and evidence outcome not present at study start	Unclear risk	Not applicable
Comparability of groups on basis of design or analysis	Low risk	OR from multivariate analysis; no detail in this brief report Earlier publications focused on different exposures; identified relevant variables (e.g., demographics, alcohol and tobacco use, body mass index, use of hormone replacement therapy, and menopause) included in logistic regression models.
Case‐control: non‐response rate	Unclear risk	Earlier report (La Vecchia 1991), with data through June 1989, noted < 3% refused to participate (8 cases, 38 controls)
Cohort: follow‐up length and adequacy (including loss to follow‐up)	Unclear risk	Not applicable