Chronic Diseases and Injuries in Canada
Volume 32, no. 3, June 2012
Unhealthy behaviours among Canadian adolescents: prevalence, trends and correlates
T. M. Gadalla, PhD
This article has been peer reviewed.
Factor-Inwentash Faculty of Social Work, University of Toronto, Toronto, Ontario, Canada
Correspondence: Tahany M. Gadalla, Factor-Inwentash Faculty of Social Work, University of Toronto, 246 Bloor Street West, Toronto, ON M5S 1V4; Tel.: (416) 946-0623; Fax: (416) 978-7072; Email: firstname.lastname@example.org
Introduction: This study examines (1) time trends in the prevalence of selected unhealthy behaviours among adolescents aged 12 to 17 years, (2) the most commonly adopted combinations of unhealthy behaviours, and (3) socio-economic and sociodemographic correlates of unhealthy behaviours among adolescents.
Methods: A secondary analysis used data collected from 13 198 Canadian Community Health Survey (CCHS) respondents in 2000/2001 and 11 050 CCHS respondents in 2007/2008.
Results: Although the proportion of adolescents consuming a healthy diet increased over the study period, about 50% are still consuming insufficient amounts of fruit and vegetables. In both cycles over one-third of adolescents aged 15 to 17 years reported drinking alcohol regularly. Income level, education level, sex, and language spoken at home were significantly associated with the odds of engaging in unhealthy behaviours among those aged 12 to 14 years, while income level was no longer associated with the odds of engaging in unhealthy behaviours among those aged 15 to 17 years. For both age groups, a language other than French or English spoken in the home was associated with a low risk of unhealthy behaviours.
Conclusion: There was a general decrease in unhealthy behaviours among younger adolescents aged 12 to 14 years.
Keywords: adolescents' health, alcohol, smoking, healthy eating, body weight, physical activity
Unhealthy behaviours in adolescence, such as smoking, physical inactivity, unhealthy eating (for example, consuming less fruit and vegetables than recommended) and alcohol drinking, contribute to chronic diseases in adulthood.Footnote 1,Footnote 2,Footnote 3 Young adults who reported having their first alcoholic drink at the age of 11 to 14 years experienced an increased risk of alcohol-related diseases,Footnote 1 such as certain cancers and heart and vascular disease,Footnote 4 as well as an increased risk of adverse impact on brain development.Footnote 4,Footnote 5 Chronic health conditions, in turn, have significant adverse effects on quality of life and productivity.Footnote 3,Footnote 6
Physical inactivity and unhealthy eating lead to overweight and obesity, risk factors for a large number of chronic health complications such as cardiovascular disease, hypertension, type 2 diabetes, stroke, sleep apnea and certain types of cancer as well as complications in pregnancy and during surgery.Footnote 7 Obesity has also been implicated as a risk factor for functional limitations and poor health-related quality of life.Footnote 8,Footnote 9
In studies using national samples of high school students in the United States, almost one-quarter were overweightFootnote 10,Footnote 11 and 13.6% obese.Footnote 11 More than three-quarters (78.4%) of a U.S. national sample of young adults aged 18 to 24 years consumed less than five fruits and vegetables per day, and 43.2% reported insufficient or no physical activity.Footnote 12 Similar rates have been observed in Canadian youth: based on national data of Canadian children aged 7 to13 years, Tremblay and Willms reported an increase of 0.1 kg/m2 per year in body mass index (BMI) between 1981 and 1996.Footnote 13 These authors also reported a 28.8% and 23.6% prevalence of overweight in boys and girls, respectively.13
Seo et al. reported that the prevalence of smoking among high school students increased from 21.9% in 2003 to 23.0% in 2005.Footnote 11 Pisetsky et al. found similar rates of current smoking among adolescents.Footnote 14 About one-third (34.3%) of students in grades 7 to 12 living in the Atlantic provinces in Canada reported smoking cigarettes.Footnote 15
Seo et al. also reported a detrimental correlation between smoking and unhealthy eating.Footnote 11 Smoking among U.S. high school students was associated with being overweight, and this association became stronger between 1999 and 2005. Footnote 11
Pisetsky et al. found that 22.0% of female and 27.7% of male high school students binge drink, that is, consume 5 or more alcoholic drinks in one sitting at least once a month.Footnote 14 In a sample of young adults aged 18 to 24 years living in the U.S., 28.9% reported being current smokers and 30.1% reported binge drinking.Footnote 12 A national survey of 4296 Canadian adolescents found that 29% of those aged 14 to 15 years reported drinking to intoxication.Footnote 16 Over half (53.6%) of students in grades 7 to 12 living in the Atlantic provinces of Canada reported using alcohol.Footnote 15
Differences exist in the prevalence of health-risk behaviours by socio-economic status, sex and ethnicity. Wardle et al. found that adolescents from more deprived neighbourhoods were more likely to have tried smoking, to eat a high fat diet and to be overweight; these differences persisted after controlling for ethnicity.Footnote 2 On the other hand, Tremblay and Willms found that levels of physical activity and sedentary behaviour partially accounted for the association between socio-economic status and overweight/obesity in Canadian children aged 7 to 11 years.Footnote 17 In a recent study of Californian adolescents aged 12 to 17 years, the prevalence of obesity increased significantly between 2001 and 2007 among lower-income adolescents but not among higher-income adolescents.Footnote 18
A number of studies have shown that, compared to adolescent boys, adolescent girls are generally more fixated on their body weight and more engaged in weight control methods, some of which are unhealthy, for example, cigarette smoking and using diet pills or laxatives.Footnote 10,Footnote 19-Footnote 21 Garry et al. also reported a strong association between the use of diet pills and vomiting/laxative-use with alcohol use and cigarette smoking in middle school students.Footnote 20 Allison et al. found that daily smoking decreased as education level increased, but that this decrease was not associated with income level.Footnote 22 More recently, Kestila et al. examined the relationship between childhood social circumstances and overweight in young adults aged 18 to 29 years.Footnote 23 The researchers found that being overweight was associated with low parental education and irregular parental employment in women, but not in men. Women who lived in rural municipalities in childhood were more likely to be obese than those from semi-urban or urban municipalities.Footnote 23
Knowing the types and frequency of adolescents’ unhealthy behaviours as well as the rate of their engagement is essential for planning prevention, intervention and outreach programs aimed at increasing the health of Canadians. Policy makers would also benefit from an examination of the time trends (years) of the unhealthy behaviours as well as the identification of groups of youth at high risk of engaging in such behaviours, information that is currently lacking. This study is an attempt to fill these gaps in knowledge. Specifically, the aim of this research is to (1) examine trends in the prevalence of obesity or overweight and unhealthy behaviours such as low physical activity, unhealthy eating (e.g. the consumption of less fruit and vegetables than recommended for this age group) and alcohol drinking in a nationally representative sample of Canadian adolescents aged 12 to 17 years between 2000/2001 and 2007/2008; (2) investigate the most common combinations of unhealthy behaviours adopted by adolescents by sex; and (3) identify the sociodemographic and economic attributes associated with engaging in unhealthy behaviours in younger as well as older adolescents.
This research used data collected in two cycles of the Canadian Community Health Survey (CCHS) under the authority of the Canadian Federal Statistics Act.Footnote 24 This cross-sectional survey, conducted every two years, uses a multistage stratified cluster probability sampling in which a dwelling is the final sampling unit. The survey sample was stratified by province/territory and urban versus rural regions within each province/territory. Sampling was designed to represent 98% of the Canadian population aged 12 years or more who lived in private dwellings in the ten provinces and the three territories. In both cycles, approximately half of the respondents were randomly selected to be interviewed face-to-face using the computer-assisted personal interviewing method, and half were interviewed by telephone using the computer-assisted telephone interviewing method.Footnote 24,Footnote 25 Introductory letters mailed to selected respondents assured them of the confidentiality laws governing the release and/or publication of collected data and of the voluntary nature of participation. Interviewers obtained verbal permission from parents/guardians to interview youth aged between 12 to 15 years and explained the purpose of collecting the data, the subjects to be covered and the need to respect a child’s right to privacy and confidentiality. If a youth could not be privately interviewed either in person or over the phone, the interview was coded as a refusal. More details about the survey design are published elsewhere.Footnote 24,Footnote 25 There were 13 198 respondents aged 12 to 17 years in the 2000/2001 survey and 11 050 in the 2007/2008 survey.
Alcohol drinking was measured using two variables: frequency of drinking and binge drinking. Frequency of drinking was based on the respondent’s drinking habits in the 12 months before the survey (regular, occasional, did not drink). A regular drinker drank alcohol once a month or more often during the year before the survey, and an occasional drinker drank alcohol less frequently. Binge drinking was defined as consuming five or more alcohol drinks in one sitting at least once a month.
Cigarette smoking was measured using one variable, frequency of smoking. Respondents were asked: "At the present time, do you smoke cigarettes daily, occasionally or not at all?" Responses were categorized as "daily smoker," "occasional smoker" and "non-smoker."
BMI classification was based on the age- and sex-specific BMI cut-off points as defined by Cole et al. for 12 to 18 year olds.Footnote 26 These, in turn, were based on pooled international data from Brazil, Great Britain, Hong Kong, Netherlands, Singapore and the U.S.Footnote 26 The authors used heights and weights of over 192 000 individuals to develop age- and sex-specific cut-off points for BMI categories for 12- to 18-year-olds. Cut-off points were specific for each sex and year of age, and ranged between 21.22 kg/m2 and 30.0 kg/m2 for boys and from 21.68 kg/m2 and 30.0 kg/m2 for girls. This variable classifies adolescents (except girls aged 15 to 17 years who were either pregnant or did not answer whether they were pregnant or not) as "obese," "overweight" or "neither obese nor overweight."
Other variables of health used in the analysis included daily consumption of fruit and vegetables (less than five servings versus five or more servings) as a marker for an unhealthy diet, and perceived general health (excellent/very good, good and fair/poor). Data on self-perceived stress were collected only from respondents 15 years or more in response to the following question: "Thinking about the amount of stress in your life, would you say that most days are not at all stressful / not very stressful / a bit stressful / quite a bit stressful / extremely stressful?"
Physical activity was measured using two variables, level of physical activity and time spent in sedentary activities. Level of physical activity categorizes respondents as being "active," for a total energy expenditure (EE) in their transportation and leisure activities of 3.0 kcal/kg/day or greater, "moderately active" for an EE of 1.5 kcal/kg/day or greater, but less than 3.0 kcal/kg/day, or "inactive" for an EE of less than 1.5 kcal/kg/day. Respondents’ energy expenditure was calculated using the frequency and time per session of each physical activity and its metabolic energy cost (MET). For example, an activity of 4 METs requires 4 times the amount of energy as compared to when the body is at rest. The amount of metabolic energy used in a 15-minute session of each leisure activity (MET) was calculated and multiplied by the number of sessions to get the total energy expenditure (EE) corresponding to each activity. Survey respondents were not asked to specify the intensity level of their activities; therefore, the MET values calculated here correspond to the low intensity value of each activity. This approach was adopted because people tend to overestimate the intensity, frequency and duration of their activities.Footnote 24
The total number of hours spent in sedentary activities in a typical week in the three months before the survey was also estimated. Sedentary activities included using a computer (including playing computer games and surfing the Internet), playing video games, watching television or videos and reading. The time spent at school or work was not included. Respondents’ sedentary activities were then classified into four categories: less than 15 hours/week, 15 to 29 hours/week, 30 to 44 hours/week and 45 or more hours/week.
Sociodemographic characteristics used in this research included sex, age group (12-14 years and 15-17 years), language spoken at home (English/French versus other), place of birth (Canada versus other), highest level of education in the household (less than secondary school degree, secondary school graduate, some post-secondary education, post-secondary graduate), and income level. However, data on income level were reported differently in the two cycles of CCHS. In the 2000/2001 cycle, income adequacy was grouped into four levels, while in the 2007/2008 cycle it was grouped into three.Footnote 24 Consequently, a direct comparison of this variable could not be carried out.
Age-specific rates of engagement in health risk behaviours for the years 2000/2001 and 2007/2008 were calculated and compared, and used chi-square (χ2) tests to compare the prevalence of unhealthy behaviours in the two cycles. χ2 tests were also used to assess the bivariate relationships between unhealthy behaviours and various sociodemographic and economic attributes.
Unhealthy behaviours with more than two levels were recoded as yes/no variables. For example, "physically inactive" was coded as yes while "active" and "moderately active" were coded as no, "daily" and "occasional" cigarette smoking were coded as yes while "not at all" was coded as no, "regular" and "occasional" alcohol drinking were coded as yes and "non-drinker" as no. Data were then aggregated to show the most common combinations of unhealthy behaviours adopted by male and female adolescents separately.Logistic regression models were used to examine the effects of sociodemographic and economic attributes associated with engaging in unhealthy behaviours in younger as well as older adolescents. Only those variables that were significantly associated with engagement in unhealthy behaviours in the bivariate tests were included in the multivariate analysis. Sampling weights were rescaled and used in all analyses. Rescaling the weights to have an average of one has two advantages. First, it takes into account the unequal probabilities of selection of survey respondents and adjusts the sample results to the demographic composition of the Canadian population so that the results represent the population of Canada and not just the sample itself. Second, it keeps the total sample size unchanged to guard against inflating the sample size for hypothesis testing. Footnote 24,Footnote 25
Table 1 shows the descriptive statistics of all the variables used in the analysis. The most notable change over the study period was a 9 percentile point increase in the proportion of adolescents consuming five or more fruits/vegetables per day (12-14 years: χ2 = 729.33, p < .001; 15-17 years: χ2 = 65.90, p < .001). There was also a marked reduction in the prevalence of cigarette smoking for both age groups (12-14 years: χ2 = 96.79, p < .001; 15-17 years: χ2 = 120.53, p < .001).
|CCHS respondents, n (%)|
|12-14 years||15-17 years|
(n = 6251)
(n = 5574)
(n = 6947)
(n = 5476)
Abbreviations: BMI, body mass index; CCHS, Canadian Community Health Survey.
|Female||2993 (47.9)||2664 (48.7)||3459 (49.8)||2705 (49.4)|
|IncomeTable 1 - Footnote a|
| Highest 30%
| 1684 (37.0)
| 1267 (32.1)
|Language spoken at home|
| 5057 (90.7)
| 2914 (89.7)
|Country of birth|
| 5551 (88.8)
| 4913 (88.9)
| 6058 (87.2)
| 4744 (87.9)
|Education within the household|
| Less than secondary school
Secondary school graduate
| 508 (8.3)
| 188 (4.3)
| 533 (7.9)
| 186 (4.2)
| Excellent/very good
| 4546 (72.7)
| 3902 (70.1)
| 4877 (70.2)
| 3749 (68.5)
|Self-perceived stressTable 1 - Footnote b|
| 2261 (41.4)
| ObeseTable 1 - Footnote c
OverweightTable 1 - Footnote d
| 310 (5.2)Table 1 - Footnote **p
| 193 (4.2)
| 295 (4.3)
| 229 (4.6)
|Daily consumption of fruit / vegetables, servings|
| < 5
| 3591(58.5)Table 1 - Footnote **p
| 2486 (50.1)
| 4050 (59.1)Table 1 - Footnote **p
| 2665 (51.6)
| 2595 (49.4)Table 1 - Footnote *p
| 2724 (51.7)
| 2699 (44.0)Table 1 - Footnote **p
| 2583 (48.5)
|Sedentary activities, hours/week|
| < 15
| 973 (30.1)Table 1 - Footnote **p
| 1345 (26.0)
| 1404 (35.7)Table 1 - Footnote **p
| 1414 (26.7)
| 185 (3.0)Table 1 - Footnote **p
| 51 (0.9)
| 1005 (14.5)Table 1 - Footnote **p
| 450 (8.2)
| 335 (5.4)Table 1 - Footnote **p
| 219 (3.9)
| 2288 (33.2)Table 1 - Footnote *p
| 1859 (34.3)
| 68 (1.1)Table 1 - Footnote **p
| 27 (0.05)
| 920 (13.2)
| 683 (12.6)
Although the data showed slight improvement in the proportion of physically active adolescents, the number of hours spent in sedentary activities showed a bigger increase; the proportion of adolescents who spent more than 45 hours/week in sedentary activities increased from 6.1% to 8.3% among younger adolescents (12-14 years: χ2 = 42.69, p < .001) and from 3.8% to 9.0% among older adolescents (15-17 years: χ2 = 170.00, p < .001). There was also a significant improvement in BMI distribution for the younger adolescents (12-14 years: χ2 = 23.43, p < .001), but not for the older ones. Similarly, the prevalence of binge drinking improved significantly for the younger group (12-14 years: χ2 = 13.30, p < .001), but not for the older one.
Table 2 shows the number of unhealthy behaviours adopted by adolescents and their distribution based on age and sex. The proportion of younger adolescents (12-14 years) who had not adopted any unhealthy behaviours increased considerably (males: 25.2% to 36.4%; females: 26.7% to 38.5%) between 2000/2001 and 2007/2008. Among older adolescents (15-17 years), this increase was more modest (males: 15.7% to 20.8%; females: 18.3% to 20.3%).
|Age group, years||CCHS survey respondents, n (%)||Number of unhealthy behaviours|
Abbreviation: CCHS, Canadian Community Health Survey. Note: All data are weighted by the rescaled weights. The average of the rescaled weights being 1, many of the data would be fractions; therefore, the totals in different analyses may not be exactly equal due to approximation.
|12-14||2000/2001Table 2 - Footnote *p|
| 820 (25.2)
| 1522 (46.7)
| 738 (22.6)
| 163 (5.0)
| 15 (0.5)
| 1041 (36.4)
| 1136 (39.7)
| 592 (20.7)
| 85 (3.0)
| 7 (0.2)
|15-17||2000/2001Table 2 - Footnote *p|
| 546 (15.7)
| 1139 (32.7)
| 999 (28.6)
| 498 (14.3)
| 307 (8.8)
|2007/2008Table 2 - Footnote **p|
| 577 (20.8)
| 899 (32.5)
| 755 (27.3)
| 367 (13.3)
| 170 (6.1)
Consuming less than five servings of fruit and vegetables was the most common unhealthy behaviour among both male and female adolescents who had adopted one such behaviour (males: 57.3%; females: 47.9%). Table 3 shows other unhealthy behaviours by frequency and sex. For male adolescents, the second most common unhealthy attributes were being overweight or obese (15.6%) and physically inactive (15.0%) followed by regular alcohol drinking (10.5%) and daily smoking (1.3%). Of female adolescents, 30.0% were inactive, 11.6% drank alcohol regularly, 9.0% were overweight or obese and 1.6% smoked daily.
The most common combination of unhealthy behaviours among adolescents with two such behaviours was insufficient consumption of fruit/vegetables and physical inactivity (35.3% in males and 51.1% in females) (Table 3). The second most common combination among male adolescents was insufficient consumption of fruit/vegetables and overweight/obesity (27.8%), while among female adolescents it was insufficient consumption of fruit/vegetables and regular alcohol drinking (13.7%). Eight percent of male adolescents and 5.7% of female adolescents with two unhealthy behaviours combined regular alcohol drinking with binge drinking. Only 1.8% of males and 1.4% of females combined regular alcohol dinking with daily cigarette smoking (Table 3).
Results of the bivariate χ2 tests show that sex, income level, education level and language spoken at home were associated with engaging in unhealthy behaviours for younger adolescents (12-14 years) while place of birth was not. For the older group (15-17 years), only sex, education level and language spoken at home were significantly associated with engaging in unhealthy behaviours while self-perceived stress level, place of birth and income were not.
Results of the logistic regression analysis indicate that education level, sex and language spoken at home were significantly associated with the probability of engaging in at least one unhealthy behaviour among adolescents (Table 4). These probabilities were slightly higher for boys aged 12 to 14 years compared with their female counterparts (odds ratio [OR] = 1.18, 95% confidence interval [CI] = 1.03-1.34), but lower for boys aged 15 to 17 years compared to females in that age range (OR = 0.83, 95% CI = 0.70-0.97). Respondents speaking languages other than English/French at home had a lower risk of engaging in unhealthy behaviours (12-14 years: OR = 0.66, 95% CI = 0.51-0.85; 15-17 years: OR = 0.60, 95% CI = 0.46-0.80). Adolescents in households where the highest level of education was a high school certificate had almost twice the risk of engaging in unhealthy behaviours compared with those in households with a post-secondary degree (12-14 years: OR = 1.93, 95% CI = 1.51-2.46; 15-17 years: OR = 1.46, 95% CI = 1.11-1.92).
In this study, I examined prevalence of smoking, obesity and overweight, physical inactivity, unhealthy eating and alcohol drinking in a nationally representative sample of Canadian adolescents in 2000/2001 and 2007/2008. This study also investigated trends of engaging in these behaviours for younger (12-14 years) and older (15-17 years) adolescents and for male and female adolescents separately, as well as the types of unhealthy behaviours adopted by adolescents and the most common combinations of such behaviours. Sociodemographic and economic correlates of engaging in unhealthy behaviours were also examined.
A limitation of this study arises from the fact that all the measures used were based on self-reported data, which is subject to bias.
While younger male adolescents had a slightly higher probability of engaging in unhealthy behaviours, older ones had a slightly lower probability compared with their female counterparts-a somewhat puzzling result that suggests the need for further research. This result underscores the importance of examining adolescents’ behaviours separately for sex and for age.
In spite of the increase in the proportion of adolescents consuming sufficient amounts of fruit and vegetables daily, in 2007/2008 approximately half were still consuming less than the recommended amount. This proportion, however, is much lower than the 78% of U.S. youth reported consuming less than the recommended amount of fruit and vegetables.Footnote 12 While the proportion of obese or overweight adolescents aged 12 to 14 years decreased from 22.2% to 18.3% over the study period, the corresponding proportion of those aged 15 to 17 years remained almost the same at 19.7%. Although these rates are lower than those observed in the 1990s,Footnote 13 they are still far from ideal and hence require the attention of health advocates and policy makers.
Over the study period, around one-third of the 15- to 17-year-olds reported drinking alcohol regularly during the previous year, a proportion similar to that reported elsewhere.Footnote 12
The logistic regression results indicated that language spoken at home and parents’ education level are the most important demographic correlates of unhealthy behaviours among adolescents. Adolescents who speak languages other than English/French at home had a much lower probability of engaging in unhealthy behaviours. Lower levels of parental education were associated with a higher probability of unhealthy behaviours among younger as well as older adolescents, evidence supported by other research findings.Footnote 23 Low income was associated with higher odds of unhealthy behaviours among younger adolescents, but not among older ones.
This study was based on secondary data analysis of nationally representative samples of adolescents aged 12 to 17 years that were collected in the 2000/2001 and 2007/2008 cycles of the CCHS. The study indicated a general decrease in unhealthy behaviours among younger adolescents aged 12 to 14 years. More outreach and health educational programs should target older adolescents with a special focus on combating the detrimental effects of unhealthy eating, physical inactivity and alcohol drinking.
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