Vol.1, No.3, 73-79 (2011)
opyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/OJPM/
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.
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
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
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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.
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-
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
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 visitindependently 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
Copyright © 2011 SciRes. http://www.scirp.org/journal/OJPM/Openly accessible at
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.
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
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.
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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.
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.
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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
Abstinent from
smoking at 5-year
OR 95% CI OR 95% CI
Non-reducers 1 1
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
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
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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.
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.
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-
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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