Interventions to reduce harm from continued tobacco use

 

Abstract

Background

It may be reasonable to try to reduce the harm from continued tobacco use amongst smokers unable or unwilling to quit. Possible approaches to reduce the exposure to toxins from smoking include reducing the amount of tobacco used, and using less toxic products. The interventions evaluated in controlled trials have predominantly attempted to reduce the number of cigarettes smoked.

Objectives

To assess the effect of interventions intended to reduce the harm from smoking on the following: biomarkers of damage caused by tobacco, biomarkers of tobacco exposure, number of cigarettes smoked, quitting, and long-term health status.

Search methods

We searched the Cochrane Tobacco Addiction Group Specialised Register in June 2010 using free text and MeSH terms for harm reduction, smoking reduction and cigarette reduction.

Selection criteria

Randomized or quasi-randomized controlled trials of interventions in tobacco users to reduce amount smoked, or to reduce harm from smoking by means other than cessation. Outcomes were change in cigarette consumption, markers of cigarette exposure and any markers of damage or benefit to health, measured at least six months from the start of the intervention.

Data collection and analysis

We pooled trials with similar interventions and outcomes using a fixed-effect model. Other studies were summarised narratively.

Main results

Sixteen trials evaluated interventions to help those who smoke, to cut down the amount smoked and three compared different types of cigarettes or potentially reduced-exposure products. Self-reported reduction in cigarettes per day (CPD) was validated by reduction in carbon monoxide (CO) levels. Most trials tested nicotine replacement therapy (NRT) to assist reduction. In a pooled analysis of nine trials, NRT significantly increased the odds of reducing CPD by 50% or more for people using nicotine gum or inhaler or a choice of product compared to placebo (n = 3429, risk ratio [RR] 1.72; 95% confidence interval [CI] 1.41 to 2.10). Where average changes from baseline were compared for different measures, CO and cotinine consistently showed smaller reductions than CPD. Whilst the effect for NRT was significant, small numbers of people in either treatment or control group successfully sustained a reduction of 50% or more. Use of NRT also significantly increased the odds of quitting (RR 1.73; 95% CI 1.36 to 2.19). One trial of bupropion failed to detect an effect on reduction or cessation. Four trials of different types of advice and instructions on reducing CPD did not provide clear evidence. One study comparing cigarettes with different tar levels and one study of carbon filters showed some reduction in exposure to some toxicants but it is unclear that the risk of harm would alter substantially. A study of an electrically heated cigarette smoking system showed some evidence of improvement in markers of cardiovascular risk.

Authors' conclusions

There is insufficient evidence about long-term benefit to support the use of interventions intended to help smokers reduce but not quit smoked tobacco use. Some people who do not wish to quit can be helped to cut down the number of cigarettes smoked and reduce their CO levels by using nicotine gum or nicotine inhaler. Because the long-term health benefit of a reduction in smoking rate is unclear, but is likely to be small, this application of NRT is more appropriately used as a precursor to quitting.

 

Plain language summary

Can smokers be helped to reduce harm by smoking fewer cigarettes or using different tobacco products

People who smoke may be unwilling or unable to stop smoking completely. Cutting down the number of cigarettes smoked daily or smoking less damaging products may reduce the harm caused by smoking. It may also be a step towards stopping smoking completely. This approach might, however, undermine the importance of quitting which has very clear health benefits. We found 16 controlled trials that tested ways to help people to cut down the number of cigarettes they smoked. We found three randomized controlled trials which tested the effects of using products designed to reduce damage, such as Potentially Reduced Exposure tobacco Products (PREPs). Eleven of the trials tested nicotine replacement therapy (NRT) as an aid to cutting down. Our combined analysis of nine of these trials (3429 smokers) found that nicotine replacement roughly doubled the odds of reducing the number of cigarettes per day by 50% or more. However, levels of carbon monoxide and cotinine (markers within the body of exposure to tobacco smoke) did not reduce by the same proportion. This suggested that there may not be a direct relationship between the reduction in number of cigarettes and the reduction in harmful effects. Although NRT helped significantly more people to cut down, few were able to sustain the reduction over time. NRT also nearly doubled the odds of quitting completely. One trial failed to find a benefit of bupropion either for cutting down or for quitting. Four trials tested advice or instructions for reducing the number of cigarettes smoked per day, and did not find clear evidence of a significant effect. We did not find any trials which reported the long-term effects on health of cutting down, and it remains uncertain how much health benefit there is from cutting down.

 

摘要

背景

持續吸菸的減害介入處置

對於無法或不願意戒菸的吸菸者，嘗試進行持續吸菸的減害介入處置可能是合理的。可能降低暴露於有害物質的方法包括降低使用的香菸量，以及使用有害物質較少的產品。在控制試驗中所評估的處置主要是嘗試減少吸菸的量。

目標

評估目標為降低吸菸的傷害的介入處置，在以下變項上的效果：菸品導致的傷害的生化標記，暴露於菸品的生化標記，使用的香菸量、戒菸，以及長期的健康狀態。

搜尋策略

我們搜尋Cochrane Tobacco Addiction Group Specialised Register中關於減害，減少吸菸，減少菸品。從2006年3月開始搜尋，直到2007年3月。

選擇標準

隨機或類隨機的控制試驗，治療目標為降低吸菸者的吸菸量，或以戒菸之外的方式來減少吸菸的傷害。結果包括香菸的消耗量的改變、香菸暴露的標記與任何對健康有害或有益的標記，測量時間是從開始進行治療後至少6個月。

資料收集與分析

我們使用固定效果模式合併有相似治療方法與結果的試驗。其他的研究則以敘述性的方式總結。

主要結論

納入的13個試驗都是評估協助吸菸者減少吸菸量的治療方式之療效。每天自述的香菸減少量(CPD)也被一氧化碳濃度的減少所驗證。大部分的試驗評估尼古丁替代療法(NRT)對於協助降低吸菸量的療效。沒有合格的研究評估可降低暴露量的產品的成效。合併8個試驗的分析顯示，使用尼古丁口嚼錠或吸入劑或其他相關產品者，相對於安慰劑組，NRT對於減少CPD會顯著增加50%以上的機會(3273位參與者, [OR] 2.02, 95% [CI] 1.55 to 2.62)。從基準期開始的平均改變，一氧化碳與柯丁尼(cotinine)一致地比CPD要來得少。雖然NRT的效果是顯著的，但是不管是治療組或控制組，能夠維持減少50%或以上的吸菸量者畢竟是少數。使用NRT也能顯著地增加戒菸的比率(OR 1.90, 95% CI 1.46 to 2.47)。一個bupropion的試驗無法發現到在降低吸菸量或戒菸上的效果。4個不同種類的降低CPD的建議與指導的試驗並沒有呈現出明確的證據。

作者結論

關於協助吸菸者減少傷害，但不戒菸的治療，並沒有足夠的證據支持其有長期的效果。有些不想戒菸的人可以被協助減少吸菸量，並以尼古丁口嚼錠或尼古丁吸入劑降低他們的一氧化碳濃度。因為降低吸菸量的長期健康效益並不明確，NRT的應用最好被當作是戒菸前的前導。

翻譯人

本摘要由彰化基督教醫院陳美雀翻譯。

此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。

總結

吸菸者可能藉由減少吸菸量或者吸傷害較少的菸品，來嘗試降低吸菸所導致的傷害。吸菸者可能不願意或無法完全戒煙。降低每天吸菸的量或吸危害較少的產品可能可以降低吸菸所帶來的傷害。這也可能是朝向完全戒菸的一個步驟。然而這個取向可能低估戒菸的重要性，而戒菸對健康的助益是非常明顯的。我們找到13個評估協助人們降低吸菸量的治療方法的控制試驗。我們並沒有發現任何隨機控制試驗是評估使用產品來減少危害，例如可能降低暴露於菸草的產品(PREPs)。10個試驗評估尼古丁替代療法(NRT)對於降低吸菸量的助益。我們對於其中8個試驗(共3273位吸菸者)的合併分析發現尼古丁替代療法對於降低每日吸菸量至50%以上，可提高為約2倍的機率。然而，一氧化碳與柯丁尼(cotinine)的濃度(體內對於暴露於吸菸的標記)並沒有同等程度地減少。這顯示吸菸量的減少與傷害效果的降低可能並沒有直接的關係。雖然NRT顯著地協助更多人降低吸菸量，很少人能持續維持。NRT也提高完全戒菸的比率至將近2倍。1個研究無法發現bupropion對於降低吸菸量或戒菸的助益。4個研究評估以建議或指導來協助降低每天的吸菸量，結果沒有發現有顯著效果的明確證據。我們沒有找到任何研究報告降低吸菸量對健康的長期效果，而降低吸菸量對健康有多少助益也仍然不清楚。