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Drug therapy
Original article
Medication use in normal weight and overweight children in a nationally representative sample of Canadian children
  1. Stefan Kuhle,
  2. Christina Fung,
  3. Paul J Veugelers
  1. School of Public Health, University of Alberta, Edmonton, Alberta, Canada.
  1. Correspondence to Dr Paul J Veugelers, School of Public Health, University of Alberta, 350 University Terrace, Edmonton, Alberta, Canada, T6G 2T4; paul.veugelers{at}ualberta.ca

Abstract

Background As overweight and obese children are more likely to develop serious medical conditions, they incur higher doctor and hospital costs compared to their normal weight counterparts. Consequently, the differential healthcare costs between obese and normal weight children may be even greater if medication use is considered.

Objective To compare medication use between normal weight and overweight children in a nationally representative sample from Canada.

Methods Data from the Canadian Health Measures Survey 2007/2009, a cross-sectional survey assessing indicators of health and wellness in Canadians, was used in the current study. The analysis included 2087 children and adolescents between 6–19 years of age with valid measures of body mass index (BMI). Poisson/negative binomial regression was used to examine the association between weight status and the number of medications taken in the last month.

Result For 6–11 year olds, the frequency of prescription, over-the-counter and natural health product (NHP) medication use did not differ between normal weight and overweight/obese children. For 12–19 year olds, overweight/obese children used prescription medication significantly more often than their normal weight peers (adjusted incidence rate ratio (IRR), 1.59; 95% CI 1.19 to 2.14), whereas for NHP the opposite was the case (adjusted IRR, 0.52; 95% CI 0.32 to 0.82). These children also used nervous system and respiratory medications more frequently than their normal weight peers.

Conclusion The findings of the present study suggest that the differential usage of prescription drugs among overweight/obese children underline the need to develop effective obesity prevention programmes and policies that may reduce the health and economic burden of childhood obesity.

https://doi.org/10.1136/archdischild-2011-301195

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    What is already known on this topic

    • Overweight/obese children incur higher doctor and hospital costs than normal weight children.

    • Prescription drug expenditures have doubled over the last decade, making it the second largest cost component in the Canadian healthcare system.

    What this study adds

    • Adolescents who are overweight/obese use more prescription medicines than those of normal weight.

    • A considerable proportion of drug expenditures could be attributed to overweight/obesity among adolescents.

    • This study underlines the need to develop effective obesity prevention programmes and policies that may reduce the health and economic burden of childhood obesity.

    Introduction

    Childhood obesity has increased considerably over the past few decades and is now a major public health concern worldwide.1 ,2 In Canada, rates of childhood obesity have tripled, with an estimated 26% of children aged 2–17 years being overweight and 8% being obese.3 ,4 Overweight often persists into adulthood and is associated with a spectrum of chronic conditions later in life, including cardiovascular disease, osteoarthritis and certain types of cancer.5 ,6 Moreover, childhood obesity is a further cause for concern given the emergence of adult onset diseases, such as type 2 diabetes and the metabolic syndrome, in childhood.7 ,8

    Excess body weight among children results in diminished quality of life for the individual.9 ,10 The growing obesity epidemic and its related morbidities place considerable financial burden on healthcare systems, with total direct costs estimated to be up to C$6.0 billion in Canada.11 More important, however, is that overweight children, like adults, are at an increased risk of developing serious medical conditions and psychosocial complications compared to their normal weight counterparts.12 ,13 Specifically, children who are overweight are at an increased risk of developing musculoskeletal problems,14 asthma,15 ,16 cardiovascular disease,17 depression,18 and sleep apnoea.19 As a result, healthcare costs and usage in overweight and obese children is already higher than in their normal weight peers.20–24

    We have previously shown that obese children between 11 and 14 years of age have 21% higher doctor and hospital costs than normal weight children.23 With prescription drug expenditures doubling in Canada and the USA over the last decade, the second largest cost component behind hospital costs in the Canadian healthcare system is medication use, which accounts for 17% of healthcare spending in Canada.25 ,26 Thus, the differential between the healthcare costs for obese and normal weight children may be even larger if medication costs are considered. In the presence of ever-rising healthcare expenditures, characterising these disparities in prescription drug use will provide a more complete picture on the burden of the current childhood obesity epidemic and can aid with healthcare planning and resource allocation. To the best of our knowledge, no study so far has compared medication use between weight status groups in children in a publicly funded healthcare system. Therefore, the objective of our study was to compare medication use between normal weight and overweight children in a nationally representative sample from Canada.

    Methods

    Study design

    The current study used data from the Canadian Health Measures Survey (CHMS). The CHMS is a representative, cross-sectional survey assessing indicators of health and wellness in Canadians between 6–79 years.27 The survey consisted of a household interview to obtain sociodemographic and health information and a visit to mobile examination centre to perform a number of physical measure tests (including blood and urine samples and a fitness test). The sampling frame of the Canadian Labour Force Survey was used to identify 15 collection sites for the mobile examination centres. Within each collection site, households were selected using the 2006 Census as the sampling frame. A detailed description of the sampling strategy is available elsewhere.27 Interviews and examinations for the CHMS were performed between 2007 and 2009. The overall response rate was 51.7%. A total of 5604 persons participated in physical examination part of the survey. The present analysis uses data from 2087 children and adolescents between 6–19 years of age. Information for the household interview for children aged 6–11 years was provided by an adult with assistance from the child; children 12 years and older answered the questions on their own where possible.

    Primary outcome and main exposure of interest

    The primary outcome was the number of medications taken by the respondent in the past month. Information on medication use was collected during the household interview. Respondents were asked to name all prescription drugs, over-the-counter (OTC) drugs and natural health products (NHP) they had been taking in the last month. Each medication was classified according to the Anatomical Therapeutic Chemical (ATC) classification system. The ATC is a classification of pharmaceutical products by target organ system.28 The main exposure was weight status (normal weight or overweight/obese) based on the age-specific and gender-specific body mass index (BMI) cut-off points for children and youth established by the International Obesity Task Force29 based on health-related adult definitions of overweight (≥25 kg/m2) and obesity (≥30 kg/m2).

    Covariates

    Gender, household education, household income adequacy and province of residence were used as covariates in the analyses. Household education was used as a three-level categorical covariate representing the highest level of educational attainment in the household (secondary school or less; some post-secondary education or college; university). Household income adequacy was considered as a three-level categorical variable that takes into account the number of people in the household and the total household income from all sources in the 12 months before the interview. Province of residence of the respondents was New Brunswick, Quebec, Ontario, Alberta, or British Columbia.

    Statistical analysis

    Descriptive data on sociodemographic factors and medication intake by weight status were reported as median or relative frequency as applicable. Associations between weight status and the number of medications taken in the last month were examined using Poisson or, in the presence of overdispersion, negative binomial regression. Separate models were built for number of prescription medications and number of any medication in each of the ATC level 1 classes A (alimentary tract and metabolism), M (musculoskeletal system), N (nervous system) and R (respiratory system), respectively. Medications in the remaining ATC domains were infrequently used and were thus not analysed further. Due to the relatively small number of respondents, propensity scores were used to adjust for potential confounders. A propensity score represents the probability that an individual had a certain exposure status given their set of covariates.30 Propensity scores for the current study were determined using predictions from a logistic regression model that included gender, household education, household income adequacy and province of residence of a respondent. All analyses were stratified by age group (6–11 and 12–19 years). Missing values for categorical variables used in the analysis were considered as separate categories but results are not presented. Estimates were obtained using sampling weights provided by Statistics Canada to account for design effect and non-response bias. Standard errors were estimated using a bootstrapping procedure with 11 degrees of freedom as recommended by Statistics Canada for this survey.27 Statistics Canada recommendations for sampling variability27 as determined by the coefficient of variation (CV) were followed: data with a moderate CV (16.6% to 33.3%) must be interpreted with caution and data with a CV of >33.3% were suppressed due to extreme sampling variability. Information based on the information of less than 10 individuals was omitted as per Statistics Canada guidelines. Stata V.11 (Stata Corp, College Station, Texas, USA) was used to perform the statistical analyses. Ethics approval was obtained from the Health Canada's Research Ethics Board for the CHMS survey31 and from the Health Research Ethics Board at the University of Alberta for the secondary data analysis in this study.

    Results

    A total of 2087 children and adolescents between 6–19 years participated in the survey and had valid information on measured BMI. Twenty-three per cent of the 6–11 year olds and 28% of the 12–19 year olds were overweight or obese. Demographic information and medication use by weight status is summarised in table 1. Prescription, OTC and NHP medication use in the last month was reported by 17, 51 and 25%, respectively, of 6–11-year-old children and 33, 70, and 22%, respectively, of 12–19-year-old children. In the younger age group, 65% of children took any type of medication in the past month, whereas this number was 83% in the 12–19 years group. Prescription medication use for the most part followed a social gradient with children from socioeconomically disadvantaged households reporting more frequent drug use (table 2).

    View this table:
    Table 1

    Demographics and medication use by weight status

    View this table:
    Table 2

    Prescription drug use by sociodemographic factors

    The overall frequency of prescription, OTC and NHP medication use did not differ between normal weight and overweight children in the 6–11 years age group. For the 12–19 year olds, overweight and obese children used prescription medications significantly more frequently in the past month than their normal weight peers (adjusted incidence rate ratio (IRR), 1.59; 95% CI 1.19 to 2.14) whereas for NHP the opposite was the case (adjusted IRR, 0.52; 95% CI 0.32 to 0.82) (table 3).

    View this table:
    Table 3

    Incidence rate ratios for taking medications in the last month

    Normal weight children used medications for the alimentary tract and metabolism more frequently than overweight and obese children in both age groups. In the 12–19 years age group, overweight and obese children had a significantly higher rate of usage of nervous system and respiratory medications. Patterns of usage of medications within each of the four ATC top-level domains did not differ between normal weight and overweight children with the notable exception of respiratory medications, which saw drugs for the treatment of obstructive airways disease as the most common ATC subclass in overweight and obese children (table 4).

    View this table:
    Table 4

    The most commonly used medication types (>10%) within each Anatomical Therapeutic Chemical (ATC) domain in normal weight and overweight/obese children in descending order of frequency

    Discussion

    Our study demonstrates that prescription medication usage was higher among overweight and obese adolescents relative to their normal weight peers. Use of OTC medications did not differ by weight status whereas NHP use was more common in normal weight children. In older children, overweight and obese children were more frequent users of nervous system and respiratory medications. Within the respiratory medication class, drugs for the treatment of obstructive airways disease were more often used by overweight and obese children than by their normal weight peers.

    Prescription drug use was fairly common in the 12–19 years old group, with one-third reporting to have used one or more prescription medications in the past month. This is comparable to recent results from the National Health and Nutrition Examination Survey (NHANES) in the US, which reported 30% of children aged 12–19 years to have used one or more prescription drugs in the past month.26 While there is limited data in the literature on the use of prescription medications in children, three studies in the US and one study in The Netherlands using prescription expenditure data consistently reported prescription drug use in about 60% of the participating children over the course of a year.32–35 The seemingly low 1-year prevalence relative to the 1-month prevalence found in our study is readily explained by the fact that only drugs that were covered by the insurance plan were included in the US and Dutch studies. By contrast, our current study assessed all prescription drugs including those not covered by the provincial insurance plan and paid for by the families. Another study using a 15-day recall of prescription drug use in Brazil found a prevalence of 20% in a birth cohort of 11-year-old children.36

    The results from our study confirm our hypothesis that the higher healthcare use observed in overweight and obese children20–24 is paralleled by a more frequent use of prescription drugs. While there was no significant difference between the two weight status groups in younger children, in the 12–19 years age group, overweight and obese children and youth took prescription drugs 59% more frequently than those in the normal weight group. Assuming equal costs for the medications, this finding would translate in 59% higher medication costs. That is, the cost differential for prescription medications may even be higher than the 21% difference for hospital and doctor costs between obese and normal weight children as previously reported by us.23 With an overweight/obesity prevalence of 28% in the sample and 59% higher medication costs, approximately 14% of drug expenditures in this age group may be attributed to overweight and obesity.37 Only two other studies have compared medication use between obese and normal weight children: a study from a regional paediatric healthcare centre in Israel found about 60% more prescriptions in obese children between 12 and 18 years compared to normal weight children.38 Data from a follow-up of the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort at age 11 years in Brazil showed that obesity is associated with 20% higher intake of medications (prescription and OTC).36 In contrast to the latter two studies, the present analysis was further able to examine which drug classes accounted for the differential between overweight and normal weight children. Most importantly, respiratory medications (ATC class R) were used twice as often by overweight children than by their normal weight counterparts. Among the most common medications in this group we found antihistamines and drugs for the treatment of obstructive airways diseases (table 4). These latter two findings reflect the higher rate of respiratory disorders, in particular asthma, in overweight and obese children as reported by us39 and others.15

    Two other medication groups that were examined in the current study are OTC medications and NHP. The former can be an indicator for barriers in access to care,40 ,41 overuse/misuse of drugs,42 and concern with health matters.43 The use of OTC medications was slightly more common in overweight children and youth in the 12–19 years age group but the result was not statistically significant. The limited sample size and the lack of variables relating to the reasons for the medication use did not allow us to further investigate this finding.

    Strengths of the current study include its nationally representative sample of Canadians and objective measurements of height and weight. Moreover, data collected from the CHMS, unlike administrative databases, includes individuals who may not have sought medical attention or treatment for their condition. A limitation of the study is the relatively small sample size, which required the analysis of overweight and obese children in one group and may have diluted more pronounced differences between obese and normal weight children. The smaller sample size also did not allow for an in-depth investigation into the contribution of sociodemographic factors. However, the use of propensity scores to adjust the regression models has helped to minimise confounding by socioeconomic status. Moreover, drugs that may lead to weight gain were not considered but are likely not relevant. The response rate was relatively low but survey results were weighted by Statistics Canada to minimise bias as a result of non-response.27 Owing to the physical burden of the assessments used in the survey such as blood sampling and fitness testing, healthier and fitter individuals may have been overrepresented relative to the general population. Therefore, any residual bias would have rather resulted in an underestimate of medication use in the overweight/obesity group. The quality of self-reported and proxy-reported data may be impacted by recall problems or differences in reporting medication between the children and their parents. We feel that the potentially lower data quality through limited recall is offset by the inclusion of all medications used, irrespective of their being covered by the insurance. Further, it has been previously shown that there is a good agreement between children and parent report of medication use.44

    To conclude, overweight and obese adolescents use prescription drugs, in particular drugs for the treatment of respiratory disorders, more frequently than their normal weight peers. The increased medication use in this group further adds to the burden on healthcare systems due to the obesity epidemic.

    Acknowledgments

    We thank Ms Irene Wong from the Statistics Canada Research Data Center at the University of Alberta for her support.

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    Footnotes

    • Contributors SK conducted the analyses and wrote the manuscript. CF contributed to the development of the manuscript. PJV conceived and supervised the study.

    • Funding The research was funded through a Canada Research Chair in Population Health and Alberta Innovates Health Solutions Health Scholarship to PJV.

    • Disclaimer While the research and analysis are based on CHMS data from Statistics Canada, all interpretations and opinions in the present study are those of the authors and do not represent the views of Statistics Canada.

    • Competing interests None.

    • Patient consent Obtained.

    • Ethics approval Ethics approval obtained from the Health Canada's Research Ethics Board for the CHMS survey and from the Health Research Ethics Board at the University of Alberta for the secondary data analysis in this study.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data sharing statement This study was based on data from Statistics Canada's CHMS Cycle 1 through a microdata research contract with Statistics Canada. All data are publicly available from the original source.