Bandolier 54 examined a Cochrane review of nicotine replacement therapy. Since then
the review has been updated, nicotine replacement therapy (NRT) is much higher on the
political agenda, and the way we look at data has changed a bit, so we thought it
worth another look, together with some cost-effectiveness.
Review
The Cochrane review [1] is typically thorough because the Cochrane Tobacco Addiction
Group has its own ongoing register of trials that is being constantly updated. This
review was of trials available up to April 2000. Included were randomised trials in
which NRT was compared to placebo or no treatment, or where different doses of NRT
were compared. Excluded were trials not reporting cessation rates or with follow-up
of less than six months.
The main outcome measure was abstinence from smoking after at least six months of
follow-up. The most rigorous definition of abstinence for each trial was used, with
biochemically validated rates if available. The meta-analysis used fixed effects odds
ratios, but since those lack intuitive meaning,
Bandolier
reports NNTs together with absolute quit rates.
Results
The main results are in Table 1, for all trials, for large trials (those with
combined placebo plus NRT patients of at least 250), and for low baseline quit rates
of less than 10%. These sensitivity analyses seemed additionally useful to test the
validity of the results, because many of the NRT trials included in the review were
small (fewer than 100 patients) and the range of quit rates without NRT was wide
(2-46% with gum, for instance).
Table: Results from nicotine replacement therapy meta-analysis with sensitivity
analysis
|
|
|
Patients stopped smoking at 6-12 months
|
|
|
|
|
NRT
|
Placebo
|
|
|
Type of NRT
|
Number of trials
|
Number/total
|
Percent
|
Number/total
|
Percent
|
NNT (95% CI)
|
|
All trials
|
| Gum |
48 |
1453/7387 |
20 |
1084/9319 |
12 |
12 (11 to 14) |
| Patch |
31 |
1384/9708 |
14 |
495/5969 |
8 |
17 (14 to 20) |
| Intranasal spray |
4 |
107/448 |
24 |
52/439 |
12 |
8 (6 to 14) |
| Inhaler |
4 |
84/490 |
14 |
44/486 |
8 |
12 (8 to 26) |
| Sublingual tablet |
2 |
49/243 |
20 |
31/245 |
13 |
13 (7 to 103) |
|
Large trials
|
| Gum |
18 |
792/5126 |
15 |
710/7308 |
10 |
17 (14 to 22) |
| Patch |
14 |
1115/8333 |
13 |
352/4615 |
8 |
17 (15 to 21) |
|
Cessation rate with control<10%
|
| Gum |
15 |
299/3370 |
9 |
315/5192 |
6 |
36 (25 to 61) |
| Patch |
17 |
482/4219 |
11 |
193/3440 |
6 |
17 (14 to 22) |
| Large trials were those with more than 250
participants in NRT and placebo groups combined |
Numbers needed to treat for nicotine replacement versus placebo or no treatment
controls were of the order of 8 to 17 for different NRT preparations using all
trials. There were many trials and patients for gum and patch, but limited
numbers for intranasal sprays, inhalers and sublingual tablets (Table 1). Between
8% and 13% of patients stopped smoking at 6-12 months without NRT, and this
increased to 14% to 24% with NRT.
Only gum and patch had trials of over 250 participants. The NNT for patch was 17
for all trials and 17 for large trials. For gum, the NNT of 12 for all trials
rose to 17 for large trials.
Only gum and patch had sufficient trials with controls cessation rates of less
than 10% for analysis. The NNT for patch was 17 for all trials and 17 for trials
with lower cessation rates. For gum, the NNT of 12 for all trials rose to 36 for
control cessation rates below 10%.
Comment
The overall result for the updated Cochrane review is similar to that obtained
previously. We can be sure that nicotine patches will almost double the number of
people stopping smoking at six to 12 months. For every 17 people using nicotine
patch for about eight weeks to help smoking cessation, one more will stop smoking
who would not have done with no patch or with placebo patch.
The background rate of cessation of smokers in general is estimated at about
1.5% a year. In the control groups in these trials, the rate of cessation is
often much higher than this, showing that people wanted to stop smoking, and that
personal motivation with some professional intervention can achieve a certain
amount on its own. Nicotine patches can almost double the rate, which must be
good. The evidence for patches is robust to sensitivity analysis, and based on a
large number of trials and patients.
The evidence for gum is a bit flakey, because the NNTs increase substantially
with larger trials and in those with lower control cessation rates. Inhalers and
sprays look effective but based on relatively small numbers of trials and
patients.
Cost effectiveness
So if nicotine patches are prescribed in general practice, is this a good buy
for health services? The argument would be that the known effects of smoking are
so awful, that by stopping people smoking we
buy
further years of life. So we should be able to compute how much the
intervention(s) cost, how many life years we obtain, and therefore the cost per
life year.
This has been done [2] off the back of a trial in which 4.5% of people stopped
smoking with GP counselling, and 9.6% stopped with counselling plus nicotine
patches (NNT 20). In the trial only one of 476 smokers who were still smoking at
the end of the first week of treatment were abstinent at one year. Calculations
were therefore based on a model that only allowed nicotine patches for a week in
those who were still smoking (based on breath carbon monoxide measurement).
The cost per life year saved was £344 to £785 depending on the age
of the patient. Other studies [3] come up with similar estimates. When examined
against a library of life-saving interventions [4], nicotine replacement therapy
is pretty cost-effective.
References:
- C Silagy et al. Nicotine replacement therapy for smoking cessation
(Cochrane Review). In: The Cochrane Library, Issue 1, 2001. Oxford: Update
Software.
- JA Stapleton et al. Prescription of transdermal nicotine patches for
smoking cessation in general practice: evaluation of cost effectiveness. Lancet
1999 354: 210-215.
- S Parrots et al. Guidance for commissioners on the cost-effectiveness of
smoking cessation interventions. Thorax 1999 53 (Suppl 5): S1-S38.
- TO Tengs et al. Five-hundred life-saving interventions and their
cost-effectiveness. Risk Analysis 1995 15:369-390.
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