Duration of suboptimal weight status and self-esteem in Hong Kong primary school children

Abstract

Hong Kong children are facing dual challenges of obesity and underweight. While the surge in obesity in the past 2 decades has drawn much attention, the substantial prevalence of underweight seems overlooked. Childhood obesity has been associated with low self-esteem (SE), but longitudinal data are scarce. Studies have considered the level of obesity at a certain time point, ignoring potential effects of the duration of suboptimal weight status (overweight or obesity and underweight). This study aimed to 1) assess the trend of suboptimal weight status in Hong Kong primary school children; 2) assess the prevalence of low SE; 3) assess cross-sectional associations between suboptimal weight status and low SE in Primary (P) 6 students; 4) assess prospective associations between duration of suboptimal weight status and low SE. Data (collected during academic year 1995/96-2001/02) were provided by the Student Health Service. Weight and height of children were measured yearly from P1 to 6. Body mass index (BMI) was calculated. Age- and sex-specific BMI cut-offs equivalent to <18.5, 23-25, >25 at 18 years were used to identify underweight, overweight and obese children, respectively. Cumulative duration of overweight or obesity (CDO), consecutive years of overweight or obesity (CYO), cumulative duration of underweight (CDU) and consecutive years of underweight (CYU) were used to assess the duration of suboptimal weight status. Students having low total and domain-specific SE were identified using the Culture Free Self-esteem Inventories 2nd Edition. Complete cases analysis was performed: 1) Binary logistic regression models were fitted to assess cross-sectional associations between weight status (independent variable) and SE (dependent variable) at P6. 2) To evaluate the effects of duration of suboptimal weight status (independent variables: CDO, CYO, CDU and CYU) on SE (dependent variable), logistic regression models were fitted. Sex-stratified analyses were conducted. Socioeconomic proxies and lifestyle behaviours were adjusted. Overweight or obesity steadily (P1 21.5%, P6 32.8%) increased while underweight was stable (P1 16.7%, P6 16.0%) throughout follow-up period. More students were persistently (P1-6) overweight or obese (15.8%) than underweight (6.6%). More boys than girls were overweight or obese. About 6% of students (boys 6.7%, girls 5.2%) reported low SE at P6. At P6, overweight or obesity was significantly associated with low total, general, social and academic SE, while underweight was only related to low social SE. Prospectively, increased CDO and CYO predicted low total, general, social and academic SE. Increased CDU and CYU only predicted low social SE. Consecutive years of suboptimal weight status (CYO and CYU) was a stronger predictor of low SE than cumulative duration of suboptimal weight status (CDO and CDU). In conclusion, overweight or obesity increased from P1 to P6 in Hong Kong primary school children. Boys were more likely to be overweight or obesity and have low total SE than girls. Both longer cumulative duration and consecutive years of suboptimal weight status prospectively predicted low total SE and domain specific SE. In general, consecutive years of suboptimal weight status was a stronger predictor of low SE than cumulative duration of suboptimal weight status.