The certainty of evidence is downgraded by imprecision or heterogeneity.
A Cochrane review «Interventions for smokeless tobacco use cessation»1 «Livingstone-Banks J, Vidyasagaran AL, Croucher R, et al. Interventions for smokeless tobacco use cessation. Cochrane Database Syst Rev 2025;4(4):CD015314 »1 included 43 studies with a total of 20 346 subjects assessing smokeless tobacco cessation. Those products are consumed orally or nasally and do not involve combustion or heating at the time of use. There was moderate-certainty evidence of increased quit rates from counselling compared with minimal support (RR 1.76, 95% CI 1.44 to 2.16; I²=69%; 21 studies, n=7417; downgraded because of heterogeneity), brief advice compared with no support (RR 1.24, 95% CI 1.03 to 1.48; I²=49%; 7 studies, n=6271; downgraded because of imprecision), and varenicline compared with placebo (RR 1.35, 95% CI 1.08 to 1.68; I²=0%; 2 studies, n=508; downgraded because of imprecision). There was low-certainty evidence (downgraded because of imprecision and risk of bias) of increased quit rates from nicotine replacement therapy compared with placebo or no medication (RR 1.18, 95% CI 1.05 to 1.33; I²=39%; 11 studies, n=2826).