Recurrent non-specific low back pain (NSLBP) affects 13 to 40 % of adolescents worldwide . Lately, it has gained considerable research attention largely because of adverse consequences such as increased medical attention, school absenteeism, functional disability and chronic pain evolving into adulthood . A recent study conducted in Zimbabwe by Chiwaridzo and Naidoo showed a high prevalence rate of recurrent NSLBP among urban high school adolescents. Unfortunately, attention and health resources in Zimbabwe have been focused mainly on preventation and treatment of adulthood low back pain. This is a cause of concern given the reported consequences of adolescent recurrent NSLBP and the inevitable potential to become a future musculoskeletal problem.
The adolescence period represents a critical stage of spinal development characterised by rapid growth. During this period, the spine is thought to be vulnerable to stresses that are common. Although many factors can lead to back pain, it is possible to hypothesise that factors contributing to increased load on the lumber spine or diminished blood supply to the area may lead to recurrent NSLBP. Personal or lifestyle-related factors such as body mass index (BMI), muscle flexibility, sports participation, smoking, prolonged sitting, carriage of heavy school bags maybe important in the development of recurrent NSLBP in adolescents. These factors are interesting from a public health perspective since they are amenable to educational strategies. There is dearth of literature regarding the factors associated with recurrent NSLBP in Zimbabwean adolescents. This creates a vacuum of validated evidence to justify any preventative strategies. An understanding of the differences in personal and lifestyle characteristics among adolescents with and without recurrent NSLBP is crucial in guiding the development of preventative actions that are context relevant, since the background of other studies may be different to ours.
Although Zimbabwean adolescents are no different from the rest of world, differences that exist in the school system, school environment, families, lifestyle and background of school children makes them different from those in other countries. With the recent positive changes in the Zimbabwean economy, there has been growing concern over increased obesity, sedentary lifestyles, and social ills such as smoking among high school adolescents. Additionally, a casual observation of the Zimbabwean scholars has shown that they carry school bags to school with items that include textbooks, sports equipment and laptops because of increased educational demands. These items may represent a substantial load if carried every day. This study was, therefore, conducted to determine the differences in personal or lifestyle-related factors between adolescents with recurrent NSLBP and those without in high schools in Harare, Zimbabwe. The factors selected were: body mass index, relative school bag weight, perceptions of school bag weight, duration and method of bag carriage, time spent sitting per day after school on entertainment activities, smoking, sports participation, and hamstring muscle flexibility.
The questionnaire used had four sections. Section A gathered information on the prevalence of recurrent NSLBP. Section B sought information related to the use of school-bags. Respondents were specifically asked questions on school bag use, perceptions of the school bag weight, duration of carriage and method of carriage. Section C captured information regarding sports participation either at school or home and the amount of hours spent in sports per week. Section D sought information on the smoking status and the amount of cigarettes smoked per week. A preliminary test and re-test reliability study showed fair to perfect kappa coefficients (0.32 to 1) of the 21 primary questions in the questionnaire. The results of the reliability study have been presented elsewhere in detail. In addition, the questionnaire was assessed for content validity by a panel of five experts in the field of musculoskeletal research yielding a scale-level content validity index (S-CVI) of 0.70..
Body weight was measured using a calibrated scale following standard procedures. The weight was considered as the average of two best measurements that agreed within 0.1 kg. Subsequently, each participant was weighed whilst carrying their school bag. The school-bags were weighed without assessing for the contents of the bag. The participating students were blinded to the fact that the study was about the relationship between recurrent NSLBP and school-bag weight. Students were told that the study was about “standing posture assessed when carrying a school bag” with no other information provided. This was done to capture the typical weight of the school bags and to avoid tampering of the school bags by students. Standing height was measured to the nearest 0.1 cm using a tape measure following instructions described in literature.