Skip navigation

Stopping smoking update 2008

Clinical bottom line

It is very, very, difficult to stop smoking without help. Only 1 in 10 who try by themselves will have stopped after six months. Most interventions to help have relatively little effect. There is only a single intervention with an NNT below 10 measured in more than 200 patients - namely varenicline. For most other interventions the effects are small, and with small effects there must be a concern about how well these small effects translate from clinical trials to clinical practice.


Data

Twelve systematic reviews and meta-analyses of smoking cessation studies, 11 of which were Cochrane reviews, have information on over 127,000 participants with cessation rates at six months or longer. All had over 300 participants in the comparison. Most used only properly randomised trials (one used controlled trials), used objective means to assess abstinence, and used either placebo or, in the case of behavioural interventions, used an appropriate control like a minimal intervention or brief advice.

A summary of the reviews is available as a downloadable PDF (36kb).

Results

Table 1 shows the main results in terms of percentage of abstinent patients with intervention and placebo or control, the relative benefit, and the NNT for one participant to be abstinent at six months who would not have been if treated with placebo. The order is by numbers of participants in the reviews. Figure 1 shows the same information graphically, ordered by the proportion of patients abstinent at six months or longer with treatment.

Table 1: Results of smoking cessation reviews, ordered by number of participants

Abstinent (%) with
Intervention
(trials six months or longer)
Number of patients
Active
Placebo
Relative benefit
(95%CI)
NNT
(95% CI)
NRT
43018
17
10
1.6 (1.5 to 1.7)
16 (14 to 17)
Bupropion
9940
19
10
2.0 (1.8 to 2.2)
11 (9 to12)
Varenicline
2023
21
8
2.7 (2.1 to 3.4)
7 (6 to 10)
Rimonabant
1049
17
11
1.5 (1.1 to 2.1)
18 (10 to 72)
Nortriptyline
975
21
10
2.1 (1.5 to 2.9)
9 (6 to 16)
Clonidine
776
25
14
1.7 (1.3 to 2.4)
9 (6 to 20)
Physician intervention
22260
8
5
1.8 (1.6 to 2.0)
30 (25 to 37)
Self help
19504
7
5
1.3 (1.2 to 1.5)
65 (45 to 110)
Nursing intervention
15205
14
11
1.4 (1.3 to 1.5)
38 (27 to 64)
Counselling
5028
12
8
1.5 (1.3 to 1.8)
26 (18 to 46)
Group therapy (vs self help)
4395
10
6
1.9 (1.5 to 2.3)
22 (16 to 33)
Cut down to quit with NRT
1833
7
3
2.0 (1.3 to 3.0)
30 (19 to 74)
Exercise
1245
18
14
1.2 (0.9 to 1.5)
24 (12 to 640)

Figure 1: Percentage of patients abstinent from smoking at six months or longer, ordered by success rate with treatment (numbers in parenthesis are numbers in the comparison)


There was a consistent response for placebo, of between 3% and 14%, with an overall average cessation rate of 8.4% in 57,867 participants on placebo. There appeared to be a lower cessation rate of 6.7% in 30,837 participants with placebo or minimal interventions in behavioural interventions, compared with 10.3% in 27,640 participants for placebo in drug interventions. This may reflect differences in populations studied.

The very large numbers of participants in nicotine replacement therapy (NRT) studies allowed investigation of a number of variables that might effect the results obtained with placebo.

The first was size. Figure 2 demonstrates a consistent cessation rate with placebo below 20%, and predominantly below 10%, with group sizes of 300 participants and above. It also shows very variable cessation rates of a few percent to almost 50% where group size was 100 or below.


Figure 2: Cessation (quit) rates with placebo in NRT studies according to number in placebo group (size of symbol proportional to number in placebo group, inset scale)


Table 2 examines other possible influences. Neither type of NRT product (gum, patch, inhaler, lozenge, or spray) nor duration of follow up beyond six months made any difference to placebo cessation rates. Participants from smoking clinics, and those with a high level of support in a group setting achieved somewhat higher rates of cessation, though below 20%.

Table 2: Influence of variables in NRT trials on cessation rates with placebo

Percent abstinent with
Variable
Number of patients
NRT
Placebo
Relative benefit
(95%CI)
NNT
(95% CI)
All trials six months or longer
43018
17
10
1.6 (1.5 to 1.7)
16 (14 to 17)
Duration of follow up
Six months
4480
20
9
1.9 (1.6 to 2.2)
9.4 (7.9 to 12)
Twelve months
24520
15
10
1.5 (1.4 to 1.6)
21 (18 to 25)
Trial setting
Community volunteers
18823
20
14
1.5 (1.4 to 1.7)
17 (14 to 20)
Smoking clinic
1283
30
19
1.6 (1.3 to 1.9)
9 (7 to 17)
Primary care
11427
11
7
1.5 (1.3 to 1.7)
25 (20 to 34)
Hospital recruitment
3236
14
10
1.3 (1.04 to 1.6)
25 (16 to 62)
Level and type of support
Low level of support
12348
13
8
1.6 (1/4 to 1.7)
20 (16 to 25)
High level support for individual
16907
15
10
1.5 (1.4 to 1.6)
21 (17 to 26)
High level support for group
7140
27
18
1.6 (1.4 to 1.7)
11 (9 to 14)
Type of NRT
Gum
19120
18
11
1.4 (1.3 to 1.5)
15 (13 to 17)
Patch
18175
16
10
1.7 (1.5 to 1.8)
17 (15 to 20)
Inhaler
986
17
9
1.9 (1.3 to 2.6)
13 (8 to 28)
Lozenge or tablet
3109
16
8
2.0 (1.6 to 2.5)
12 (10 to 17)
Nasal spray
887
24
12
2.0 (1.5 to 2.7)
8 (6 to 14)

 

Comment

This very large body of data from many different interventions conducted in a variety of settings, shows that with placebo or no treatment after six months or longer the overall result for smoking cessation is low, at about 10%. The information allows the conclusion that small studies can give highly variable and misleading results, especially where the group size is below 200 participants.

There are some very clear messages:

  1. It is very, very, difficult to stop smoking without help. About 90% of people who try will be smoking again six months later, and only 1 in 10 will have stopped.
  2. Most interventions to help have relatively little effect. There is only a single intervention with an NNT below 10 measured in more than 200 patients - namely varenicline.
  3. For most other interventions the effects are small, and with small effects there must be a concern about how well these small effects translate from clinical trials to clinical practice.