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| Journal of the New Zealand Medical Association,
27-February-2009, Vol 122 No 1290
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Has smoking prevalence markedly decreased in
New Zealand despite more cigarettes released for sale?
Murray Laugesen
In its report to the incoming government in November 2008,
the Ministry of Health noted that “Since 2003 there has been a 5% fall in
the total number of people who smoke every
day.”1 This refers to the National Health
Survey result showing daily adult smoking prevalence had fallen 4.8 percentage
points between 2003 and 2007, from 22.9% to
18.1%.2 As smoking prevalence is now the bottom
line for measuring success in tobacco control, success depends on health surveys
to call the results correctly.
Despite every statistical precaution being taken, surveys
still depend on eliciting truthful answers. For illegal drugs, this requires
urine testing. For tobacco smoking we rely on self-report. However, public
opinion against smoking is now severe. In a telephone poll in 2006, 52% of
adults supported a ban on the sale of all tobacco
products,3 while in 2007, 76% said smoking is
‘not at all acceptable’ at outdoor children’s
playgrounds.4
Surveys tend to under-report community levels of smoking,
but (for reasons of cost) few surveys report biochemically-validated results,
which would detect those responders who report their smoking incorrectly. For
example, testing for cotinine (a by-product of nicotine in saliva) has shown
national surveys underestimated smoking prevalence by 0.6, 2.8, and 4.4
percentage points in the United States, England, and Poland respectively.
Cotinine concentrations in those misclassified as
non-smokers were indicative of high levels of smoke
intake.5 In 1997, in Christchurch, pregnant
women tested for serum cotinine showed they under-reported smoking prevalence by
5.5 percentage points, meaning that 22% of the smokers would otherwise have been
unidentified as such by their midwife or
doctor.6
In particular, health surveys encourage healthier responders
and/or responses. New Zealand-wide health surveys to date—in
19907, 1993,
1997,8 2003,9
and 20072—have reported cigarette smoking
prevalences respectively 3.0, 4.0, 0.7, 2.1, and 4.9 percentage points below
that of ACNielsen’s commercial survey in that
year.10 Census smoking prevalence was
intermediate between NZHS and ACNielsen’s results (Table 1).
As a reality check, trends in numbers smoking were compared
against cigarettes and tobacco volumes released, as given by Customs excise
data. If smoking prevalence (the percentage of adults who smoke) decreases, then
fewer smoke, and the volume of demand for cigarettes decreases as expected. If,
however, the cigarette supply holds up, remaining smokers must be buying and
smoking more on average.
MethodFocusing on ages 15 years and over from 1996 to 2007,
tobacco and cigarettes released for sale from Statistics New Zealand were
compared against daily smoking prevalence reported from the periodic New Zealand
health surveys during these years, the Census smoking questions in 1996 and
2006, and by the annual ACNielsen commercial survey of cigarette smoking.
Statistics New Zealand annually publish Customs data on
tobacco and cigarette volumes released for
sale,11 and on resident population aged 15 and
over.12 Tobacco for hand-rolling was estimated
to produce 2 million roll-your-own (RYO) cigarettes per tonne, based on an
estimated national average tobacco weight of 0.5 g per RYO cigarette in
2006.13
All smoking prevalence surveys involved visits to
homes. To enable cross-survey comparison only daily cigarette smoking prevalence
was considered, defined to include both factory-made and RYO cigarette smoking.
Results were not standardised for differences in age structure of the
population; instead crude prevalence data were used to estimate actual numbers
of smokers in each year, for appropriate comparison with the numbers of
cigarettes released for sale.
The ACNielsen cigarette survey purchased by the
Ministry of Health from 1982 to 2007 was based on an annual omnibus survey
asking about various consumer items (cars, whiskey), and used a show card of
various tobacco products to ask about regular use. Smoking is thus accepted as
normal consumer behaviour in a way not possible in a health survey.
The NZHS of 1996/7 was mainly fielded in
1997.14 The 2002-3 NZHS, based on
computer-assisted personal interviews, was mainly in the field in
2003.9 The Census asked a question on cigarette
smoking in March 1996 and March 2006. The Census, being filled in by parents,
tends to under-report smoking at age 15 to 19 years, compared with the ACNielsen
survey, in which the teenager is interviewed individually. Of adults age 15
years and over, 8.6% gave an unusable answer to the Census smoking question, and
daily smoking prevalence was estimated from the 91% giving usable
answers.15
The 2006-7 NZHS was in the field from October 2006 to
November 2007, and thus mainly reports on the 2007
year.2 The 2006 and 2008 Tobacco Use surveys
and the 2007 Alcohol and Drug Use surveys only included smokers aged 15 to 64
years and are not reported here, but four government surveys in 2006-7 were
available for age-standardised comparisons for ages 15 to 64 years.
The Health Sponsorship Council’s Monitor is a
telephone survey of 1500 to 2000 people age 15 years and
over4 annually from 2003 to 2007, excepting
2006.
ResultsAll tobacco sold is smoking tobacco, and 99% is smoked as
cigarettes, as analysed from tobacco manufacturers’ annual returns to the
Ministry of Health.17 Factory-made cigarettes
accounted for 69% and RYO tobacco for 30% of the dry weight of all tobacco
used.17
Cigarettes released for sale—In
contrast, total cigarettes released, including factory-made and RYOs, rose by
7.5%, from 3957 million in 2003 to 4253 million in
200711,17 (Table 1).
Numbers of smokers—NZHS reported a
17% decrease in numbers smoking in 2007; that is, 125,000 fewer smokers (Table
1). The ACNielsen survey, however, showed only a 1.5% decrease in smoking
population from 2003 to 2007, and the Census showed a 1% decrease from 1996 to
2006.
Smoking prevalence (Table 1)—The NZHS
reported a sharp decrease in daily smoking prevalence from 22.8 in 2002-3 to
18.1% in 2006-7. (The value for 2006-7 age-standardised to the 2006 census value
was 17.8 %.) ACNielsen reported a gradual decline in smoking prevalence: 26% in
1996-7, 23.6% in 2006, and 23% in 2007—a decline of only 3 percentage
points in 10 years (Table 1), but showed no decline between 2004 and 2007 (Table
1).
Table 1. Changes in proportions and numbers
smoking, versus cigarettes
released for sale,
1996–2007
Source:
Cigarettes,10,17 Resident
population,11 AC
Nielsen,9 New Zealand Health
Surveys,1,7,8
Census.14 Numbers smoking estimated from
survey prevalence fraction × resident population.
The Census reported a 3-percentage points decrease in
smoking prevalence over 10
years, from 23.7% in 1996 to 20.7% of adults in 2006. This
was paralleled by a similar increase in the percentage of
never-smokers, while the percentage of ex-smokers remained at 21% in both
Censuses, indicating that the proportion quitting was matched by the proportion
resuming smoking.
Comparisons, based on daily smoking at ages 15 to 64 years,
and age-standardised against the 2006 Census, showed that the lowest smoking
prevalence was given by the 2007 New Zealand Health
Survey,8,16 though the three 2007 surveys (New
Zealand Health Survey, Alcohol and Drug Survey, and the 2008 Tobacco Use Survey)
had overlapping confidence limits. The narrow confidence intervals of the Census
did not overlap the confidence limits of the 2007 or 2008
surveys.17 Thus three Ministry of Health
surveys in 2007–8 reported lower smoking prevalence in 2007 than the
Census of March 2006.
Action on Smoking and Health (ASH) national surveys show
smoking prevalence at 14–15 years of age decreased steadily from 1999 to
2007. By 2007, these students populated the 15–24 year age group. The New
Zealand Health Surveys found smoking prevalence for 15-24 year-olds decreased
3.3 percentage points, from 27% in 2003 to 23.7% in 2007, equal to 9,400 fewer
youth smoking.
After smoking was banned in all workplaces and hospitality
venues from December 2004, the proportion of adults reporting it was “not
at all acceptable” to smoke at outdoor sports fields or courts, increased
from 35–37% in 2003–05, to 51% in
2007.4
DiscussionAs Table 1 shows, smoking prevalence values in 2006, 2007,
and 2008 were lower than in 2003. Also, smoking prevalence was recorded as lower
in 2007–8 than in (the Census of) 2006. The question is, how credible are
the lower smoking prevalences found in 2007–8, and how to interpret them?
NZHS results from 2003 and 2007, equate to 125,000 fewer
smokers, a 17% decrease in numbers of adults smoking in 4 years. (Table 1) The
numbers of cigarettes released to the market increased 7.5%, however, during
these 4 years, from 2003 to 2007—an increase of 296 million in cigarettes
released annually (Table 1).
These two trends are incompatible. For the NZHS result to be
compatible with cigarette volumes released, remaining smokers would have to buy
30% more cigarettes per day [100*1.075/(1-0.17) =130], those previously smoking
20 a day and still smoking would need to buy 26 cigarettes a day.
The 2006 Census recorded smoking prevalence to be three
percentage points below the value from the 1996 Census. If this decrease was due
to quitting, the proportion of former smokers (21% in 1996, 21% in 2006) should
have increased. Instead, the proportion which had never smoked increased 3
percentage points, suggesting no change attributable to smoking cessation
between 1996 and 2006.
What factors might explain the 125 000 decrease in numbers
smoking reported by the New Zealand Health Surveys from 2003 to 2007?.
Firstly, how much is explained by survey
methods and demographics? For example, how much of the NZHS decrease is
confirmed by other surveys? As Table 1 shows, 12,000 fewer smokers or 1.5% of
125,000 can be explained by the AC Nielsen survey 2003 to 2007. Again, how much
can be explained by changing age structure of the population?
Age-standardisation of the health survey data to the 2006
Census population (Ministry of Health data, unpublished 2008) would narrow the
decrease in prevalence from 4.8 percentage points in Table 1, to 4.5 percentage
points, equivalent to 6% of the decrease in numbers of smokers. The 95% upper
confidence limit for the NZHS in 2007 was 19.0%, which reduces the decrease
since 2003 by 19%. Finally, 9400 fewer youth taking up smoking would account for
7.5% of the 2003–7 decrease in smoking numbers at age 15 years and above.
Thus in total, these factors account at best for 34% of the NZHS decrease in
numbers smoking from 2003 to 2007.
Secondly, was this a smokefree law effect? The
evidence suggests not. AC Nielsen’s survey showed 25% smoked in 2003, 23%
in 2004, and 23.5% in 2005. The Smokefree Environments Amendment Bill banning
smoking in bars and remaining workplaces was enacted in December 2003, and took
effect from December 2004. Any effect of this legislation on smoking prevalence
was in place by 2004, and does not explain a decrease in smoking prevalence
between the Census of 2006 and the New Zealand Health Survey result of
2007.
Thirdly, did smoking decrease due to graphic
cigarette packet warnings? No. Regulations required manufacturers to put new
warnings on sale between February and August 2008. The Health Survey, however,
was in the field in 2006–7 before these regulations took effect, so
smokers responding to NZHS had not yet seen graphic warnings on their cigarette
packets.
Fourthly, was this a price effect? No. Price
increases tend to lower sales. Cigarette excise and prices, however, remained
the same in real terms from 2001 to 2007 inclusive.
Lastly, is the 2007 New Zealand Health Survey
defective in a unique way? No; the 2007 Alcohol and Drug Survey gave a similar
low result, and the confidence limits overlap. The New Zealand Health Survey
result is not an outlier on its own. Rather these two health surveys may both
have been prone to a health bias in 2007 favouring a lower reported smoking
prevalence.
The decline in smoking prevalence from 2003 to 2007 reported
by the New Zealand Health Surveys is implausible and incompatible with the
increased volumes of cigarettes released for sale. This was not due to
commercial fluctuations in volumes released for sale, as tobacco volumes used in
manufacture show similar annual trends.17
The one possible cause of the apparent 2007 decrease in
smoking prevalence (which is not seen in the 2006 surveys) is the increased
unacceptability of smoking that was detected in the Health Sponsorship Council
monitor of 2007.4 Social undesirability of
smoking may have influenced some smokers to either opt out of responding to the
survey as a whole or to the smoking questions in particular, or disown their
smoking when responding.
Admitting to smoking is embarrassing for many smokers. There
is no biochemical proof that this was the case in the New Zealand Health Survey,
but for future health surveys it would be advisable to validate reported smoking
status, by testing salivary cotinine or exhaled carbon monoxide. Although
cotinine tests are expensive, such costs are only a small fraction of the total
cost of a national smoking survey, and essential to its correct interpretation.
There is no other way to measure for changes in the tendency for smokers to
under-report their smoking.
Until future surveys can be validated, the rate of recent
decline in smoking is best judged by the Census, namely 3 percentage points in
10 years, at which rate it would take 70 years to reach near-zero smoking.
If smoking prevalence is falling no faster than indicated by
the 1996–2006 Censuses, ending the cigarette deaths epidemic (4500 deaths
a year) requires intervention from Government, and not just the health sector.
Government can induce marked decreases in smoking prevalence, as in 1987 to
1991, when adult smoking prevalence declined from 30% to 26%; successive
cash-strapped governments repeatedly increased tobacco excise above the level of
inflation.
Government last increased the real tobacco excise rate in
2000. Annual excise adjustments for inflation have since kept the price of
smoking of factory-made cigarettes high. However nearly half of all smokers now
smoke RYOs, for 4 or 5 dollars a day.11 The
price of a cup of coffee buys enough tobacco for 12 RYO cigarettes.
Unsurprisingly, smoking prevalence overall is reducing
extremely slowly, despite greater government funding for a wider range of stop
smoking programmes and products since 2000. The tobacco excise rate on
factory-made cigarettes, when adjusted for incomes, is one of the highest among
industrialized nations, so that any government seeking extra revenue may
hesitate to raise it much. Moreover, if the excise rate is simultaneously
increased on loose RYO tobacco by the same percentage, the effect on smoking
prevalence would be blunted by more smokers shifting to the cheaper RYOs instead
of quitting smoking.
As in 2000,17,18 increasing
the tobacco excise rates evenly on all tobacco products is unlikely to
gain revenue or reduce smoking prevalence.
Action is now required to focus on the real
problem—RYO smoking is cheap and available at half the cost of smoking
factory-made cigarettes. The lower tax on RYOs deprives government of over $300
million annually,17 and dissuades smokers from
quitting. It is necessary to raise the excise on RYO cigarettes to the same
level per cigarette as for factory-made cigarettes. This would require
a doubling of the current excise per gram on loose tobacco, probably phased in
over several steps.
Competing interests: None (Murray
Laugesen is a public health physician and independent contract researcher). No
funding was received for this study.
Author information: Murray Laugesen, QSO,
Health New Zealand Ltd, Lyttelton, Christchurch
Correspondence: Dr Murray Laugesen, 36
Winchester St, Lyttelton, Christchurch 8082, New Zealand. Email: hnz@healthnz.co.nz or chair@smokeless.org.nz; Website: www.healthnz.co.nz
References:
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