Smoking reduction did not promote future smoking cessation in a general population

doi:10.4236/ojpm.2011.13011

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Vol.1, No.3, 73-79 (2011)

doi:10.4236/ojpm.2011.13011

Open Journal of Preventive Medicine

Smoking reduction did not promote future smoking

cessation in a general population

Charlotta Pisinger1*, Mette Aadahl1, Ulla Toft1, Torben Jørgensen1,2

1Research Centre for Prevention and Health, Glostrup University Hospital, The Capital Region of Denmark, Copenhagen, Denmark;

*Corresponding Author: chpi@regionh.dk

2Faculty of Health Science, Copenhagen University, Copenhagen, Denmark.

Received 21 August 2011; revised 28 September 2011; accepted 14 October 2011.

ABSTRACT

Introduction: Smoking reduction (SR) has been

introduced as a strategy for smokers who are

unwilling or unable to quit. We wanted to investi

tigate whet her S R at on e-y e a r foll ow-u p i n creased

the probability of abstinence from smoking at

three and five-year follow-up. Methods: we in-

cluded a random sample from a general popu-

lation, the Inter99 study, Copenhag en, Denmark.

A total of 1975 participants were daily smokers

(from both the intervention and the control

group) with information on tobacco consump-

tion at both baseline and one-year follow-up

(year 1999 to 2001). Of these, 112 had reduced

their tobacco consumption substantially, by mi-

nimum 50%, at one-year follow-up. Information

on tobacco consumption and smoking status

was available on 1441 and 1308 participants at

three-year and five-year follow-up, respectively.

Outcome was self-reported point abstinence at

three and five-year follow-up. Logistic regres-

sion analyses were adjusted for confounders.

Results: One out of five smokers (20.5%) had

maintained their reduced tobacco consumption

at five-year follow-up. About twice as many re-

ducers as non-reducers reported that they had

tried to quit sin ce baseline (p < 0.05). In adjusted

logistic regression analyses we found no asso-

ciation between SR at one-year follow- up and

being point abs tinent a t three -ye ar (OR: 0.5 7; CI:

0.28 - 1.15) or five-year follow-up (OR: 1.08;CI:

0.56 - 2.09). Conclusions: Our study, including

smokers from a general population found no

association between substantial SR and future

smoking cessation at three- and five-year fol-

low-up. No studies so far have reported that SR

undermines smoking cessation, but it is still

controversial whether SR significantly increases

future smoking cessatio n.

Keywords: Smoking Cessation; Smoking

Reduction; Tobacco Consumption

1. INTRODUCTION

Smoking is still the leading preventable cause of death

in the western countries [1,2]. Smoking reduction (SR),

i.e. a decrease in number of cigarettes smoked daily, has

been introduced as a strategy for the majority of smokers

who are not motivated to quit in near future or unable to

quit. Smoking reduction, also called controlled smoking

or harm reduction is a controversial area. A burning

question is how SR relates to success of quit attempts in

later years. Does SR increase or decrease the probability

of future abstinence? Several papers have tried to answer

this question [3-20] but we lack more knowledge from

an unselected sample of smokers from a general popula-

tion. This is of great importance before implementing

SR as a population-based strategy.

Previous studies can be split into three types: a) Ran-

domised controlled trials (RCT) testing the efficacy of

nicotine replacement therapy (NRT) to help reluctant

smokers reduce their tobacco consumption [4,7,9,11-13].

All smokers included were smokers willing to reduce

and instructed to reduce. Only one study compared re-

ducers with non-reducers when reporting future absti-

nence [13]. The other trials compared smokers receiving

NRT with smokers receiving placebo. b) Papers report-

ing on self-selected reducers [3,6,8,14,16-20]. Smokers

in these studies were not encouraged to reduce. Some

studies have been population-based surveys reporting

spontaneous changes in tobacco consumption [6,14,16,

18-20]; others have reported results from smoking cessa-

tion trials [3,8,17,20]. c) Finally, a few RCTs have ran-

domised smokers reluctant to quit in near future to re-

duction with assistance versus no treatment [5,10,15].

Many of the studies were in selected smokers (female

C. Pisinger et al. / Open Journal of Preventive Medicine 1 (2011) 73-79

prisoners, young women, twins, old, coloured, heavy or

light smokers or smokers with chronic diseases) [3,8,

13-18]. Others reported old data [14] or were at risk of

recall bias [17,19]. Even though about half of the studies

[7,11-14,17-20] indicate that smoking reduction/sub-

stantial reduction increases the rate of future smoking

cessation the subject is still controversial.

In a large Danish population-based intervention study,

Inter99, we found that SR was feasible and that it in-

creased motivation to quit at one-year follow-up [21].

The study is not a randomized test of reduction, but

rather a prospective examination of self-selected redu-

cers vs. non-reducers.

The aim of this paper is to investigate whether sub-

stantial reduction in daily tobacco consumption (50% or

more) at one-year follow-up increased the probability of

abstinence from smoking at three and five-year fol-

low-up. This will be done in a large sample of daily

smokers from a general population.

2. METHODS

The Inter 99 study. Inter99 is a population-based in-

tervention study initiated in March 1999 and ended in

April 2006. The study design is described in detail else-

where [22,23]. The aim of the study was to prevent car-

diovascular disease by non-pharmacological intervention.

The study was performed at the Research Centre for

Prevention and Health [24], Glostrup University Hospi-

tal, Copenhagen, Denmark, and was approved by The

Copenhagen County Ethical Committee (KA 98155) and

the National Board of Health. Written informed consent

was obtained from all participants. The study was regis-

tered in the Clinical Trials.gov (NCT00289237). The

study population (N = 61,301) comprised all individuals

in specific age-groups (30 to 60 years) from a defined

area of Copenhagen. From this study population three

age- and sex-stratified random samples were drawn: two

for the intervention groups (a total of 13,016: a high in-

tensity intervention group A (N = 11,708), and a low

intensity intervention group B (N = 1308)); and one for

the control group C (N = 5246). The groups were pre-

randomised. Baseline participation rates were 52.5% in

the intervention group and 63.1% in the control group.

Persons included in this paper. At baseline (year

1999 to 2001) a total of 3684 persons included in the

intervention (N = 2408) and control groups (N = 1,276)

stated to be daily smokers and 3663 (99.4%) gave in-

formation on their daily tobacco consumption. Out of

these, 2385 (65.1%) reported their smoking status at

one-year follow-up and 1975 (53.9%) were daily smok-

ers with information on tobacco consumption at both

baseline and one-year follow-up (group AB: N = 1086

and group C: N = 889). A total of 112 daily smokers (89

in the intervention groups and 23 in the control group)

had reduced their tobacco consumption at one-year fol-

low-up. Information on daily tobacco consumption was

available on 1441 (73%) and 1308 (66%) participants, at

three-year and five-year follow-up, respectively, of those

who were daily smokers at baseline.

Smoking reduction intervention. The primary focus of

the intervention was smoking cessation and all smokers

were in a lifestyle consultation with a health professional

strongly encouraged to quit. Smokers unwilling to, or

not ready to quit were encouraged to think more about

the harm and disadvantages of smoking, and to reduce

their tobacco consumption as much as possible. The aim

was to quit “one day”. Additionally, at baseline, reluc-

tant daily smokers in intervention group A were offered

participation in group-based SR intervention and 2% of

them accepted and attended the groups. The smoking

reduction intervention has been described in detail else-

where[21].

Definition of smoking redu ction. We measured “grams

of tobacco” in the following way: 1 cigarette = 1 gram, 1

gram pipe tobacco = 1 gram, 1 cheroot = 3 grams, 1 ci-

gar = 5 grams. Smoking reduction was defined as mini-

mum 50% reduction of daily tobacco consumption from

baseline to one-year follow-up. This cut-point has been

used in several studies investigating health effects of SR

[25].

Definition of smoking cessation. Abstinence from

smoking was defined as self-reported point abstinence,

e.g.: reported to be daily smoker at baseline and to have

quit at the time of the follow-up visit―independently of

smoking status at other follow-up visits. Thus, a person

could be point abstinent at three-year follow-up, but

smoke at five year-follow-up. Abstinence has been vali-

dated (serum cotinine < 20 ng/ml) in the intervention

groups, but not in the control group. For details: [26].

Questionnaires. All subjects completed comprehen-

sive self-report questionnaires. Characteristics of the stu-

dy population included self-reported socio-demographic

measures, smoking-related measures, and measures of

lifestyle and health.

Socioeconomic status was defined by length of voca-

tional training/higher education, after finishing basic

school education (e.g. unskilled worker = 0 years, green

keeper assistant = 1½ year, carpenter = 3½ years, teacher

= 4 years, medical doctor = 6 years). Categories: One

year or less, two to three years, four years or more.

Dietary quality score: a three-class variable was gen-

erated from a 52-item food frequency questionnaire

(reference period: one week), based on intake of four

food-groups/nutrients (fish, vegetable, fruit and fat). The

score has been validated [27]. Categories: healthy, ac-

ceptable and unhealthy diet.

C. Pisinger et al. / Open Journal of Preventive Medicine 1 (2011) 73-79

Physical activity was based on self-reported leisure

time physical activities. Categories: mainly sedentary,

moderate activity, regular sport/exercise, athletic train-

ing or participation in competitive sports. The question

was developed by Saltin B. [28] and has later been vali-

dated in a population-based study [29].

Alcohol consumption was self-reported as mean con-

sumption of units of beer/strong beer, wine and spirits

per week. “Recommended” = less than 15 units of alco-

hol weekly for women, and 22 units for men.

Body mass index (BMI) was calculated as kg/m2.

Health related quality of life was measured by version

1 of the Short Form 12 (SF-12), which is a generic

measure [30], and a valid, practical and reliable alterna-

tive to the 36-item Short Form 36 (SF-36). Two scales

are created, one reflecting the mental functioning and the

other the physical functioning. Higher scores indicate

better health. The summary scores were calculated using

the Medical Outcomes Study scoring system [30,31].

Chronic cough: self-reported cough of at least three

months duration in the last two years.

Statistical Analyses

All data processing was done with the SPSS 19.0

software (SPSS Inc., Chicago, IL, USA). Pearson Chi-

Square test and One-way ANOVA were used to look at

baseline differences between reducers and non-reducers

at one-year follow-up. Tobacco consumption and age

showed clear heteroscedasticity and was analysed by

Independent-Samples Man-Whitney U test.

To investigate whether SR at one-year follow-up was

associated with future smoking cessation we used logis-

tic regression analyses. Point abstinence at three and

five-year follow-up was outcome and SR of 50% or

more at one-year follow-up was the independent variable.

We adjusted for 1) factors we know influence smoking

cessation: intervention or control group, sex, age at

smoking debut, socio economic status, motivation to quit

and tobacco consumption at baseline and 2) factors that

significantly differed between reducers and non-reducers

in this study: age, diet and number of previous quit at-

tempts. In order to test whether there was a different

effect of SR on smoking cessation by intervention or

control group, we tested the interaction between group

and SR. The model was controlled by the Hosmer-Le-

meshow goodness-of-fit test.

3. RESULTS

At baseline reducers had a significantly healthier diet,

more previous quit attempts and they were older than

non-reducers (Table 1).

Tobacco consumption was four grams higher in re-

ducers than non-reducers, but this was not statistically

significant. Socio-demographic measures, other smoking

related measures, self-reported physical and mental

health and other measures of lifestyle did not differ sig-

nificantly in reducers and non-reducers.

About twice as many reducers as non-reducers reported

Table 1. Baseline characteristics of reducers (tobacco consumption reduced by at 50% or more compared with baseline) and non-

reducers at one-year follow-up.

Reducers Non-reducers p

N N

Sex = men (%) 112 52.7 1863 50.6 0.672

Age (mean, SD) 112 48.71 (±7.1) 1863 46.83 (±8.6) 0.043

Socioeconomic status = high (%) 104 47.1 1720 38.1 0.120

Occupational status = employed (%) 110 83.6 1850 80.6 0.432

Living with partner = yes (%) 111 73.9 1832 78.3 0.271

Age at smoking debut (mean, ±SD) 108 17.60 (±4.7) 1848 16.99 (±4.2) 0.146

Tobacco consumption (mean, ±SD) 112 21.67 (±16.0) 1863 17.53 (±8.0) 0.065

Number of previous quit attempts (mean, ±SD) 102 5.34 (±15.5) 1787 2.50 (±5.8) 0.027

Diet = unhealthy (%) 105 16.2 1784 27.5 0.004

Alcohol consumption = higher than recommended (%) 110 20.9 1787 23.7 0.607

Physical activity in leisure time = sedentary (%) 110 27.3 1818 27.8 0.488

Chronic cough a. = yes (%) 89 14.6 997 12.1 0.497

Body mass index (mean, ±SD) 112 25.75 (±3.6) 1854 25.33 (±4.3) 0.306

Self-rated health = fair/poor (%) 112 9.8 1853 12.8 0.297

Health related quality of life (SF-12) physical score 102 49.82 (±7.7) 1713 50.77 (±7.9) 0.236

Health related quality of life (SF-12) mental score 102 52.12 (±7.8) 1713 51.09 (±9.2) 0.266

. only answered by persons who reported cough.

C. Pisinger et al. / Open Journal of Preventive Medicine 1 (2011) 73-79

at both three and five-year follow-up that they had been

smoke-free within the last 12 months and/or had tried to

quit since baseline; the differences were significant (p <

0.05) (Figure 1).

The mean number of quit attempts from baseline to

five-year follow-up was 2.52 (SD ± 5.1) in non-reducers

and 3.79 (SD ± 6.4) in reducers. The difference was not

statistically significant (p = 0.148).

In adjusted logistic regression analyses we found no

association between reduced tobacco consumption at

one-year follow-up and being point abstinent at three- or

five-year follow-up. Actually, reducers had slightly

lower probability of having quit at three year follow-up

than non-reducers, although the difference was not sta-

tistically significant (Table 2).

We found no interaction between group and reduced

tobacco consumption, indicating that the effect of reduc-

tion on long-term abstinence was the same in the inter-

vention group as the control group.

Of those who had reduced at one-year follow-up and

attended three-year and five-year follow-up 19.6% (N =

22) and 20.5% (N = 23), respectively, had still reduced

their tobacco consumption by 50% or more.

4. DISCUSSION

In this population-based cohort we found that suc-

cessful reduction of tobacco consumption was associated

with higher incidence of quit attempts but did not in-

crease abstinence from smoking in the future. Only one

out of five reducers could keep the low tobacco con-

sumption on long-term. Reducers had a significantly

healthier diet, higher age and more previous quit at-

tempts at baseline than non-reducers.

Smoking reduction has been a hot topic in the last

decade. Before implementing this new tobacco control

strategy world-wide we need following evidence: 1) Is

SR feasible, also on a population-based level? 2) Has SR

a health benefit? and 3) Does SR increase future smok-

ing cessation or at least not undermine it? This paper

contributes to the third answer. Several studies have re-

ported a significantly positive association between SR

and future smoking cessation [7,11-14,17-20]. Others,

including our study, found no significant effect of SR on

future smoking cessation [3-6,8,9,15].

An important explanation for the different conclusions

may be the different definition of smoking reduction.

Some have looked at levels of reduction [8,14,18], oth-

ers have defined reduction as a change from daily to

non-daily smoking [16], reduction to below 15 cigarettes

per day [19] or any reduction in tobacco consumption

[3,6,17]. Different duration of follow-up may also have

an influence. The shortest follow-up has been four

months, the longest nine years [14]. Other methodologi-

cal differences may be of importance. Several studies

testing the efficacy of NRT to achieve SR investigated

future abstinence. Five out of six of these studies com-

pared smokers trying to reduce with NRT with smokers

trying to reduce with placebo/without NRT and can not

answer the research question [4,7,9,11,12]. Only one of

the studies compared reducers with non reducers [13].

Self-selection may also play a role as many of the trials

offered free NRT [3,4,7-9,11-13,17]. Also, many studies

did not include confounders [3,4,6-8,10,12,13,15]. In our

study, in unadjusted analyses, we found that SR actually

*p < 0.05

Figure 1. Percentage of daily smokers reporting quit attempts. Reducers (daily smokers who had reduced by 50% or more from

baseline to 1 year follow-up) compared with non-reducers.

C. Pisinger et al. / Open Journal of Preventive Medicine 1 (2011) 73-79

Table 2. Probability of long-term abstinence from smoking in

reducers (tobacco consumption reduced by at 50% or more

compared with baseline) and non-reducers. N = 1593.

Abstinent from

smoking at 3-year

follow-up

Abstinent from

smoking at 5-year

follow-up

OR 95% CI OR 95% CI

Non-reducers 1 1

Reducers

Unadjusted 0.54 0.28 - 1.04 0.97 0.52 - 1.82

Adjusted a 0.57 0.28 - 1.15 1.08 0.56 - 2.09

aAdjusted for group, age, sex, age at smoking debut, motivation to quit,

number of previous quit attempts, tobacco consumption, diet and socioeco-

nomic status at baseline.

decreased the probability of abstinence at three-year

follow-up.

Very important studies are those randomising smokers

to reduction or no reduction/usual care [5,10,15]. Only

one out of three of these studies showed significantly

increased abstinence rates [10]. Most previous popula-

tion-based studies have, in contrary to our study, found a

positive association between SR and future smoking

cessation [14,16,18-20]. However, three of these studies

were on selected smokers; one study was in older smok-

ers [18], one in young women [16], one in twins [14].

Additionally, one population-based study used recalled

tobacco consumption one year before study start, with

high risk of recall bias [19] and another was old, looking

at changes in consumption from 1975 to 1981 to predict

abstinence [14].

A review from 2006 stated that SR increases the

probability of future cessation [32], but in our opinion,

this should be modified to: no studies have shown that

SR undermines future cessation. Another general finding

is that prospective studies have shown that smoking re-

duction has to be substantial to show an effect on future

cessation [10,14,16,18-20].

Previous studies have reported that reducers were

characterised by high tobacco consumption, and bad

health [33-35]. In this study the mean tobacco consump-

tion was (non-significantly) higher, about four grams

more per day, in reducers than in non-reducers, but re-

ducers in our study did not report worse health than

non-reducers. Two factors could explain this difference

in health. Firstly, time of studies. E.g. the large study by

Godtfredsen et al. was performed on changes in smoking

patterns in the 1970ies/early 1980ies. At that time to-

bacco reduction was not introduced as a strategy in to-

bacco control and smoking was unrestricted everywhere.

Therefore, smoking reduction was probably a choice for

those who had bad health/smoking-related symptoms

and were unable to smoke as much as previously. Sec-

ondly, smokers unable or unwilling to quit were en-

couraged to reduce in the Inter99 intervention groups,

even young smokers without any symptoms. Overall

reducers in our study seemed to live a little healthier and

to be a little better educated. This gives us a picture of

heavy-smokers with many quit attempts, trying to live

healthy, but being unable to quit.

The finding that reducers showed a significant in-

crease in ‘being smoke-free within the past 12 months’

and ‘had tried to quit’, but not an increase in point-

prevalent abstinence could seem contradictory. Our in-

terpretation is, that reducers do wish to and do try to quit,

but their quit attempts fail. The many quit attempts after

SR is good news, as many have feared that SR would be

pretext for doing nothing, being content with the reduced

level of smoking.

Weaknesses and limitations. The major weakness of

our study is the lack of validation of the tobacco con-

sumption. In the smoking cessation part of this study the

misclassification rate of the quitters was 16% [36]. Thus,

it is also probable that tobacco consumption was under-

reported. Also, the total sample of 112 reducers is very

small and is likely underpowered to show much differ-

ences between groups in subsequent cessation.

The definition of ‘successful reduction’ can be dis-

cussed. We could as well have defined reduction as

smoking 10 cigarettes less, or below 15 grams of to-

bacco. Our definition of reduction was chosen partly

because many other studies have used this definition

[5,7,11,12,15,37] and partly because smokers who re-

duce their tobacco consumption compensate by inhaling

deeper. Therefore, reduction has to be substantial to have

any health benefit [25]. One of the problems with our

definition is that light smokers can halve their tobacco

consumption without reducing very much.

We must also consider the influence of the SR inter-

vention. In this paper we included participants from both

the intervention groups and the control group, but most

of the reducers were from the intervention group. As

only 2% of the smokers in high intensity intervention

group A accepted and attended the group-based SR in-

tervention we assumed that the influence of the SR in-

tervention was minimal. We found no interaction be-

tween group and effect of SR on smoking cessation,

supporting that the effect of SR was the same in the in-

tervention and the control group.

Finally, the relatively low participation rate may have

caused selection bias. The study population was an un-

selected random sample of a general population, but in a

baseline publication we found that participation rate was

higher in younger women than in younger men, and it

increased with increasing age until 55 years of age after

C. Pisinger et al. / Open Journal of Preventive Medicine 1 (2011) 73-79

which it declined. The participants in the intervention

group did not differ from those in the control group, re-

garding former admissions for all causes, IHD, CVD,

and diabetes [22]. Residual confounding can not be ex-

cluded and unknown confounding should always be a

matter of concern. Drop-out may also have caused selec-

tion bias, but we had information on about three out of

four baseline smokers on long term. High baseline to-

bacco consumption and continuous smoking was found

to be associated with drop-out.

Strengths. The study is large and daily smokers were

randomly included from a general population. There

were no differences in tobacco related or socio-demo-

graphic measures between daily smokers in the control

group and the intervention group at baseline, except a

higher wish to quit in the intervention group [38]. We

have included relevant confounders, used relevant statis-

tical analyses and we have a long follow-up.

5. CONCLUSIONS

Our study including many smokers from a general

population found no association between SR and future

smoking cessation at three- and five-year follow-up. No

studies so far have reported that SR undermines smoking

cessation, but it is still controversial whether SR signifi-

cantly promotes future smoking cessation.

6. ACKNOWLEDGEMENTS

We thank the whole Inter99-staff and all persons participating in the

study. Also, we thank the funding providers. Both those who funded

this paper and those who funded the Inter99 study: Helsefonden; Dan-

ish Medical Research Council; The Danish Centre for Evaluation and

Health Technology Assessment; Novo Nordisk; Copenhagen County;

Danish Heart Foundation; The Danish Pharmaceutical Association;

Augustinus Foundation; Becket Foundation; Ib Henriksens Founda-

tion.

The study was initiated by Torben Jorgensen, Knut Borch-Johnsen,

Troels Thomsen and Hans Ibsen. The Steering Committee of the In-

ter99 study: Professor D.M.Sci. Torben Jorgensen (principal investi-

gator), Professor D.M.Sci., Knut Borch-Johnsen (principal investigator

on the diabetes part) and Ph.D. MPH Charlotta Pisinger.

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