Musculoskeletal Problems in Overweight and Obese Children

Interview

An all-age, computer-generated sample of 150 registered patients per participating full-time family physician was invited to participate in an elaborate, face-to-face, multiple-choice health interview until the target number of 80 patients per physician had been reached. For nonresponders, attempts to contact (when possible), reason not to participate, sex, age, and zip code were documented. Trained interviewers performed the interviews, and the interviews were evenly distributed among 4 consecutive 3-month periods to adjust for seasonal fluctuations. Items used for this study included age, self-reported height and weight, and self-reported musculoskeletal symptoms during the previous 2 weeks. If children were younger than 12 years, a proxy interview was carried out with a parent. To increase readability, the information provided by the parents is reported as if it were information provided by the children themselves.

Morbidity Registration

Morbidity data on the interviewed children were derived from the electronic medical records. The physicians registered all health problems reported during a consultation and coded the diagnosis using the International Classification of Primary Care (ICPC). The ICPC codes used to identify musculoskeletal problems are displayed in the Supplemental Appendix, which is available online at http://www.annfammed.org/cgi/content/full/7/4/352/DC1). This survey was episode orientated, meaning that different consultations concerning the same health problem were clustered into 1 disease episode. Baseline characteristics (such as age and sex) were derived from patient records.

Overweight and Obesity

The body mass index (BMI) was used as a measure of overweight and obesity in the children²¹ and was based on self-reported weight and height. A standard developed for age-specific overweight and obesity BMI cutoff points in Dutch children was used to determine the presence of overweight and obesity in the study population.²² These cutoff points are almost identical to the recommended worldwide standard definition of overweight and obesity.²³

Study Population

We analyzed interview data and corresponding physicians’ morbidity registration data of the 2- to 17-year-old children. Only Dutch natives were included to reduce selection bias related to language and to enhance compatibility with BMI cutoff values that had been developed for native Dutch children. Children under the age of 2 years were excluded because obesity is not defined for this group. Among 2,719 eligible children, we analyzed data for 2,459 (90%) for which we had height and weight information. A weighting factor was applied to compensate for differences between registration periods per practice. Children of normal weight and children with overweight and obesity contributed equal amounts of follow-up time.

Analysis

Using age- and sex-specific BMI cutoff value curves for Dutch native children,²² the children were divided into 3 groups: normal weight, overweight, and obese children. Because numbers were too small in the overweight and obese group to assess dose-effect relationships accurately, we chose to analyze overweight and obese children as 1 group. We have calculated odds ratios (ORs) and 95% confidence intervals (CIs) comparing the overweight and obese children with the normal weight children. Odds ratios and confidence intervals not including 1 were considered significant. t tests and χ² analyses, as appropriate, were used to examine differences between these 2 groups. Significance was set at P <.05. We distinguished 2 age-groups, namely, children younger and older than 12 years of age, because of the proxy interview for children younger than 12 years. We calculated Mantel-Haenszel odds ratios to assess possible clustering of patients within physician practices. Analyses were conducted using Statistical Package for the Social Sciences, version 15.0 (SPSS Inc, Chicago, Illinois).

Ethical Approval

The study was carried out according to Dutch legislation on privacy. The Dutch Data Protection Authority approved the privacy regulation of the study. According to Dutch legislation, obtaining informed consent is not obligatory for observational studies.

Participant Characteristics

In total, 2,459 children were included in the analysis; 319 (13.0%) were overweight or obese, 219 (8.9%) and 100 (4.1%), respectively. There was no significant difference between the children of normal weight and overweight and obese children in mean age or in the distribution of boys and girls within the age subgroups. Clustering within physician practices did not affect our outcome, as Mantel-Haenszel odds ratios were comparable to crude odds ratios.

Self-Reported Musculoskeletal problems

Self-reported musculoskeletal problems are shown in Table 1⇓. Overweight and obese children in both age-groups (2 to 11 years and 12 to 17 years) reported significantly more musculoskeletal problems in daily life than did normal-weight children (OR = 1.86; 95% CI, 1.18–2.93; and OR = 1.69 95% CI, 1.08–2.65, respectively). Children aged 2 to 11 years who were overweight or obese reported neck and back pain more often than did the normal-weight children in that age category (OR = 2.60; 95% CI, 1.30–5.19). The total group of children who were overweight and obese reported more lower extremity problems than did the total normal-weight group of children (OR = 1.62; 95% CI, 1.09–2.41). We were able to split these lower extremity problems in a subgroup of hip and knee problems and a subgroup of ankle and foot problems. Ankle and foot problems were significantly more common in the total group and in the youngest age-group of overweight and obese children compared with these groups of normal-weight children (OR = 1.92; 95% CI, 1.15–3.20; and OR = 2.27; 95% CI, 1.15–4.47, respectively). Rates of self-reported upper extremity problems did not differ between overweight and obese children and normal-weight children for either age subgroup.

Musculoskeletal Problems Reported in Family Practice

Episodes of health problems derived from the electronic medical record are displayed in Table 2⇓. Among children aged 12 to 17 years, overweight and obese children consulted their family physicians more frequently with lower extremity problems (OR = 1.92; 95% CI, 1.05–3.51). Regarding upper extremity problems and neck and back problems, there was no difference in consultation rate between children who were not overweight and the overweight and obese children.

Limitations

We used self-reported weight and height to determine the BMI, which may have introduced misclassification. We believe, however, that possible misclassification is limited, because we used face-to-face interviews, which promote validity of answers.³¹ Furthermore, people will tend to underestimate weight and overestimate height, resulting in an underestimation of the number of overweight and obese children. It is, therefore, not likely that the possible misclassification will have affected the positive relation found in this study. Our findings are supported by those of Strauss,³² who compared self-reported with actual weight and height. The study showed small differences in weight, but it did not have an impact in the assessment of obesity-related morbidity.

Although there was a 35% nonresponse for the interview, we argue that selection bias was limited. Our participants were sampled independently of general practice consultation, and the children in our sample, compared with data from Statistics Netherlands, were representative (by sex, age, and region) of the Dutch childhood population. Although approximately 10% of data on height and/or weight was missing, we believe the missing data were random, because the health interview was elaborate and covered many more topics than obesity and musculoskeletal problems.

Our study shows that overweight and obese children more frequently report musculoskeletal problems in daily life than do normal-weight children. In addition to more self-reported musculoskeletal problems in overweight and obese children, we also found that overweight and obese children older than 12 years sought medical help more frequently for their lower extremity problems than did their normal-weight peers.