Gritz 1992.
Methods | Setting: HMO, USA Recruitment: members of HMO agreeing to participate in a Preventive Health Behaviour study and completing a baseline survey (unselected ‐ not informed that study was focussed on smoking) | |
Participants | 1396 female smokers, average age 38, 42% smoked 15 to 24 cpd | |
Interventions | No face‐to‐face contact; 5 follow‐up interviews in 2 years ∙ Self‐help programme mailed in 6 weekly instalments; manuals tailored to the concerns of female smokers and addressing weight gain, social support, stress, and coping mechanisms ∙ Control ‐ no materials; same schedule of follow‐up phone calls | |
Outcomes | Sustained abstinence at 1 month, 6 months, 12 months, and 18 months Validation: saliva cotinine < 15 ng/mL, but due to low success in obtaining samples, unadjusted rates used. No difference in disconfirmation rates between intervention and control groups | |
Notes | The strictest measure of abstinence extracted gives the lowest P value for the difference between groups; all other measures show a smaller difference in quit rates | |
Risk of bias | ||
Bias | Authors' judgement | Support for judgement |
Random sequence generation (selection bias) | Unclear risk | Randomised; method not described |
Allocation concealment (selection bias) | Unclear risk | No details given |
Blinding (performance bias and detection bias) All outcomes | Low risk | Control group participants not aware of the nature of the intervention; participants did not know study was aimed at smoking cessation Biochemical validation conducted; not used due to low success in obtaining samples, but no difference in disconfirmation between groups, suggesting differential misreport unlikely |
Incomplete outcome data (attrition bias) All outcomes | Low risk | 12.7% lost to follow‐up at 18 months Number in each group at baseline not stated, so losses not included as smokers in meta‐analysis Similar losses across groups, so no effect on estimate |