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| Journal of the New Zealand Medical Association,
26-July-2002, Vol 115 No 1158
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Cigarette smoking, pocket money and socioeconomic status:
results from a national survey of 4th form
students in 2000
Robert Scragg, Murray Laugesen, Elizabeth Robinson
Tobacco smoking remains the major preventable public health
issue for New Zealand at the beginning of the
21st century. Previous surveys of
4th form students carried out in the 1990s
indicated that the proportion of adolescents smoking daily increased by more
than a third from the early 1990s to 1997,1,2
although data for 1999 indicate that cigarette smoking may be declining in girls
but not in boys.3 The factors currently
involved in determining why adolescents become smokers will continue in many
cases to adversely affect their health status well into the middle of this
century.
A number of risk factors for adolescent smoking have been
identified. These include unmodifiable factors, such as female gender, Maori
ethnicity and low school socio-economic decile, and modifiable risk factors such
as parental smoking, adolescent watching of televised (tobacco sponsored) sports
programmes, and the opinion that smoking is not harmful to
health.1,4 Tobacco sponsorship has been
outlawed since 1995. However, the population attributable risks associated with
the remaining two modifiable variables, 23% for parental smoking and 7% for
believing that smoking is not harmful to
health,4 indicate that other modifiable factors
associated with the adolescent smoking need to be identified if successful
prevention strategies are to be developed.
Previous international studies suggest that the availability
of money is a risk factor for adolescent smoking. Positive associations between
pocket money and smoking have been reported from a survey of 10-11 and 13-14
year old children in Barcelona,5 and from a
national survey of French children aged 12-18
years.6 In the latter survey, the association
was independent of socioeconomic status. An Australian study of schools in
south-western and central Sydney, where there is a large concentration of
Middle-Eastern and Asian students, reported that students with more than $20 per
week pocket money were 55% more likely to be smokers than students with less
pocket money.7
There appear to be no previous New Zealand surveys of pocket
money and adolescent smoking. The purpose of the current report is to
investigate whether the availability of pocket money and socio-economic status
are risk factors for smoking in a national survey of
4th Form students.
MethodsNational surveys of tobacco
smoking and purchasing by fourth-form students were carried out in November of
1992, 1997, 1998 and 1999. Details of previous surveys have been
reported.1,3,4
A further survey was carried out in November 2000. All New Zealand schools with
4th form students were invited to participate.
The school response rate was 72% (327 out of 455 approached).
Students anonymously answered a one page questionnaire on age, sex, ethnicity (self-assigned), smoking behaviour (frequency of smoking, quantity of cigarettes per week, preferred brand(s) of cigarettes, and source and accessibility of cigarettes). Students were also asked how much pocket money they received in a usual month (30 days). The Ministry of Education classification of schools by socio-economic decile (from the low of 1 to high of 10) was used to code students for socioeconomic status (SES).8 Consent for the survey was obtained from school principals in place of parents. The Ministry of Health Auckland Ethics Committee gave permission to survey without formal referral to their committee. Schools returned questionnaires from 31652 students out of 45536 on school rolls (70% student response). Analyses were restricted to 14 and 15 year olds, and to those with known sex, ethnicity and smoking status. Excluded were students of: age 13 years (n=245) or 16 years (423) or unknown (176); unknown sex (93); unknown ethnicity (889); and smoking status unknown (456); leaving questionnaires from 29370 for analyses. All statistical analyses were made using SUDAAN (Release 7.5.6, 2000) which corrects standard errors and confidence intervals for any design effect from clustering of students by school. Unconditional logistic regression and logit models for ordinal and nominal outcomes were used to estimate adjusted odds ratios, which were converted to relative risks.9 In ethnic comparisons, “Other” students (n=377) have been combined with European. The population attributable risk was calculated by estimating the attributable proportion for the exposed cases within each exposure category using standard methods.10 ResultsThe sample comprised 14793 girls
(Maori 2488, Pacific Islands 793, Asian 965, European/Other 10547) and 14577
boys (Maori 2212, Pacific Islands 892, Asian 1112, European/Other 10361).
Smoking daily or more varied with ethnicity, in girls being Maori 37.1%, Pacific
19.4%, Asian 5.1% and European/Other 12.2%, and in boys being Maori 24.2%,
Pacific 16.8%, Asian 9.4% and European/Other 12.2%. The ethnic-specific
proportions for smoking monthly or more, in girls were Maori 51.1%, Pacific
31.3%, Asian 9.0% and European/Other 28.8%, and in boys were Maori 33.8%,
Pacific 25.8%, Asian 14.6% and European/Other 23.4%.
Table 1 shows the distribution of smoking category by school
SES decile and sex. Daily smoking varied inversely with school SES decile, the
variation from deciles 1 and 2 combined to deciles 9 and 10 combined being 26.7%
to 8.0% for girls (p<0.0001) and 17.6% to 12.3% for boys (p<0.0001). In
contrast, the variation from the bottom two deciles to the top two deciles in
the proportion of students smoking
>monthly was significant for
girls (from 39.6% to 22.9%, p<0.0001) but not for boys (from 24.6% to 24.2%,
p=0.18).
Table 1. Distribution of smoking status by sex and
school socio-economic decile.
Table 2 shows the association between the amount of pocket
money each student received in the last 30 days and demographic variables
(percentages in the table sum across rows). In univariate analyses, pocket money
was not related to sex (p=0.7), but 15 year-old students were more likely to
have received more than $30 in the last 30 days than 14 year olds (p<0.0001).
With regard to ethnicity, Maori students received the greatest amount of pocket
money, followed in order by European/Other, Asian and Pacific (p<0.0001).
Surprisingly, students in low SES decile schools received greater amounts of
pocket money than those in high SES decile schools (p=0.02). However, in
multivariate analyses using proportional odds models with a cumulative logit
link for ordinal responses, which adjusted for other variables in Table 2, only
age and ethnicity continued to be associated with the amount of pocket money
received (p<0.0001). In contrast, school SES decile was no longer associated
with pocket money amount after adjusting for age, ethnicity and sex
(p=0.5).
The distribution of smoking status by amount of pocket money
received in the last 30 days is shown for in Table 3 for girls and boys
separately, since there was a significant interaction (p<0.05) between sex
and pocket money on smoking prevalence. In separate generalised multinomial
logit models for girls and boys, smoking rates increased with increasing pocket
money (p<0.0001 ), but this increase was more marked for girls. As pocket
money increased from $10 dollars or less to $30 dollars or more, the percentage
of girls smoking at least monthly increased from 20.9% to 38.5%, whereas the
corresponding increase for boys was 18.0% from to 29.3%.
Table 2. Distribution in pocket money (dollars) per
month among demographic subgroups.
Percentages sum to 100% across rows. Table 3. Distribution of smoking status by pocket money
(dollars) in the last month (30 days), all students (male and female) in 2000
4th form survey.
Table 4 shows relative risks of daily smoking and
>monthly smoking associated
with various demographic variables, controlling for each other. Both smoking
measures were related to the amount of pocket money in each sex. Compared with
students who received $0-10 in the last 30 days, those receiving >$30 were
89% more likely to smoke daily and 73% more likely to smoke
>monthly among girls, and
68% more likely to smoke daily and 57% more likely to smoke
>monthly among boys. Smoking
daily or >monthly were also
related to older age and ethnicity (Maori highest risk, Asian lowest risk) in
each sex. However, school SES decile was inversely associated with smoking in
girls only, with deciles 1 and 2 combined being 97% more likely to smoke daily,
and 31% more likely to smoke
>monthly, than deciles 9 and
10 combined. In contrast, for boys, school SES decile was not related to either
daily or >monthly
smoking.
Among smokers, the amount of pocket money in the last 30
days was related to their source of cigarettes. For the four pocket money
categories - $0-10, $11-20, $21-30, >$30 in last 30 days - the proportions of
smokers who bought their own cigarettes were, respectively, 22.1%, 24.4%, 27.6%
and 35.1% (p<0.0001). The proportion of smokers who received cigarettes from
a family member (parent and/or sibling) also increased with increasing amount of
pocket money, being 24.2%, 25.7%, 27.1% and 29.2% (p<0.0001) for the above
four pocket money categories, respectively. In contrast, the use of friends as a
source was lowest for those receiving >$30 pocket money, compared with
students receiving $0-10 in the last 30 days (60.5% v 64.5%,
p<0.0001).
The proportion of students smoking monthly or more often,
that could be attributed to receiving more than $10 pocket money in the last 30
days, was calculated using the adjusted sex-specific relative risks in Table 4
and the sex-specific number of students smoking
>monthly for each pocket
money category (derived from Table 3). The attributable proportion was 30.4%
(1378/4537) for girls and 24.7% (854/3455) for boys.
DiscussionThe results of this national survey
of fourth form students indicate a positive association between the amount of
pocket money and risk of cigarette smoking in both sexes, independently of
socio-economic status.
These findings do not appear to have been reported before in
New Zealand adolescents, but confirm previous studies in Spain, France and
Australia.5-7 The observation of the high
proportion of students in SES deciles 1 and 2 who received >$30 pocket money
in the last 30 days was unexpected (Table 2). The positive association between
the amount of pocket money and smoking prevalence was consistent in both sexes,
and showed a dose response relationship (Table 4). The possibility of this
association being causal is supported by the observation among smokers that
students receiving >$30 pocket money in the last 30 days were most likely to
self-purchase cigarettes and were least reliant on their friends for obtaining
cigarettes.
The finding that the association between smoking and amount
of pocket money was independent of socio-economic status (Table 4) indicates
that other factors underlie this association. A key factor appears to be
parental attitudes and behaviour towards smoking. The association between family
as a source of cigarettes and amount of pocket money received by adolescent
smokers shows the link in parental behaviour regarding the provision of both
pocket money and cigarettes to adolescents. Not only are parents the primary
source of pocket money, but previous research also indicates that parental
smoking is a risk factor for adolescent
smoking.3
Table 4. Relative risk (95% confidence intervals) of
daily smoking and smoking
>monthly, by demographic
variables and amount of pocket money (dollars) in the last month (30 days); each
variable adjusted for all other variables in the table - students in 2000
4th form survey.
*Calculated from odds ratios estimated by logistic
regression.
Since this is a cross-sectional study, the associations
reported do not prove causation. It is possible that the amount of pocket money
received by students is a marker of other attitudinal changes occurring during
adolescence that are the primary determinants for choosing to smoke. Moreover,
we did not ask about money earned outside the home, which some students may not
have counted when reporting their pocket money. Further research is required to
clarify this. However, if the association is causal, the calculation that 30% of
female, and 25% of male, adolescent smoking can be attributed to receiving more
than $10 per month pocket money suggests that developing parental strategies
around the allocation of pocket money may have major benefits in limiting
adolescent smoking.
In contrast with the findings for pocket money, the
association between school SES decile and smoking prevalence showed a different
pattern. Both daily smoking and smoking
>monthly were inversely
associated with SES decile in girls only (Table 4). In boys, daily smoking was
unrelated, while >monthly
smoking was positively related, to SES decile (Table 4). Our measure of
socio-economic status, based on a single aggregate value for each school, is not
ideal for classifying students individually. However, it seems unlikely that any
measurement error arising from using school SES deciles can explain these
inconsistent results between sexes. Rather, more plausible conclusions are that
socio-economic status has greater importance as a risk factor among girls than
boys, or that there are other unmeasured confounders related to socio-economic
status in girls but not boys.
In summary, we have found that cigarette smoking is
positively related to pocket money amount in adolescents, independent of
socio-economic status. This finding may have important public health
significance, but further research is required to determine if the association
is causal. If it is, then media campaigns have a key role to alert families that
controlling the money supply to adolescents could slow their progression of
smoking. The key role of tobacco taxation in keeping the price of cigarettes
high, beyond the affordability of adolescents is clear, but needs to be
complemented by publicity campaigns to inform families that pocket money may be
going up in smoke.
Author Information:
Robert Scragg, Senior Lecturer in Epidemiology, Department of Community
Health, University of Auckland; Murray Laugesen, Public Health Physician, Health
New Zealand; Elizabeth Robinson, Biostatistician, Department of Community
Health, University of Auckland, Auckland.
Acknowledgements:
The survey was carried out by Action on Smoking and Health (ASH). Funding
was provided by the Ministry of Health.
Correspondence: Dr
Robert Scragg, Dept of Community Health, University of Auckland, Private Bag,
Auckland. Fax (09) 373 7624, Email: r.scragg@auckland.ac.nz.
References:
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