Life-course social disparities in body mass index trajectories across adulthood: cohort study evidence from China health and nutrition survey
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eLife assessment
This work shows that higher socioeconomic status is associated with a higher risk of obesity, which should inform China's obesity public health programs and policies, and also be of interest to other countries and communities. The evidence supporting the conclusions is strong, but the data analysis is incomplete and would benefit from more rigorous approaches.
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Abstract
Background
The social disparities in obesity may originate in early life or in adulthood, and the associations of socioeconomic position (SEP) with obesity could alter over time. It is unclear how lifetime-specific and life-course SEP influence adult obesity development in China.
Methods
Based on the China Health and Nutrition Survey (CHNS), three SEP-related indicators, including the father’s occupational position and the participant’s education and occupational position, were obtained. The life-course socioeconomic changes and a cumulative SEP score were established to represent the life-course SEP of the participants in the study. The growth mixture modeling was used to identify BMI trajectories in adulthood. Multinomial logistic regression was adopted to assess the associations between SEP and adult BMI trajectories.
Results
A total of 3,138 participants were included in the study. A positive correlation was found between the paternal occupational position, the participants’ occupational position, education, and obesity in males, whereas an inverse correlation was observed among females. Males who experienced social upward mobility or remained stable high SEP during the follow-up had 2.31 and 2.52-fold risks of progressive obesity compared to those with a stable-low SEP. Among females, stable high SEP in both childhood and adulthood was associated with lower risks of progressive obesity (OR = 0.63, 95% CI: 0.43–0.94). Higher risks of obesity were associated with the life-course cumulative SEP score among males, while the opposite relationship was observed among females.
Conclusions
The associations between life-course SEP and BMI development trajectories differed significantly by gender. Special emphasis should be placed on males experiencing upward and stable high socioeconomic change.
Article activity feed
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eLife assessment
This work shows that higher socioeconomic status is associated with a higher risk of obesity, which should inform China's obesity public health programs and policies, and also be of interest to other countries and communities. The evidence supporting the conclusions is strong, but the data analysis is incomplete and would benefit from more rigorous approaches.
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Reviewer #1 (Public Review):
Overall, the paper by Dang and colleagues is an interesting addition to the field. This study investigates the relationship between socioeconomic status and lifetime obesity using group-based trajectory modeling. The authors identified three trajectories overall, the most prevalent being stable normal BMI. Overall, higher SES was associated with a greater risk of obesity, which is contradictory to studies that examine the relationship among developed countries. Their findings and conclusions are supported by their analysis/data, however, some consideration and additional details are needed to help understand and be more confident in the final results.
Strengths of this study include:
- The use of novel techniques to investigate the relationship between SES and lifetime obesity, which is important for …
Reviewer #1 (Public Review):
Overall, the paper by Dang and colleagues is an interesting addition to the field. This study investigates the relationship between socioeconomic status and lifetime obesity using group-based trajectory modeling. The authors identified three trajectories overall, the most prevalent being stable normal BMI. Overall, higher SES was associated with a greater risk of obesity, which is contradictory to studies that examine the relationship among developed countries. Their findings and conclusions are supported by their analysis/data, however, some consideration and additional details are needed to help understand and be more confident in the final results.
Strengths of this study include:
- The use of novel techniques to investigate the relationship between SES and lifetime obesity, which is important for understanding the life course of disease and for designing future public health interventions and strategies.
- A large sample size.
- The use of a population-based sampling strategy to recruit participants, which helps the generalizability of findings and limits volunteer bias.
- The availability of data on SES and height/weight over a 20-year follow-up, including objectively measured weight and height.
- The availability of important confounders (e.g., physical activity, energy intake).While overall it is an interesting study, there are some considerations and unclarities that should be addressed.
Weaknesses of this study include:
- Lack of clarity on how the authors conceptualize and define socioeconomic status in some sections of the paper. A limitation is the definition of SES only encompasses educational attainment and occupation, and not other aspects (e.g. income, social class). However, most studies published to date also focus mostly on education and occupation.
- A large majority (~90%) of participants were excluded from the analysis due to missing data on exposures and outcomes. This is a substantial proportion, and it is quite possible that this may have resulted in selection bias for those included vs. those not included, and may limit the generalizability of the findings.
- As with all studies that use self-reported data, there is some potential for information bias. However, the authors do acknowledge this as a limitation in their study.
- There is a lack of clarity with some of the methods (e.g. how multinomial logistic regression was used, latent classes, and how confounders were chosen). The paper would benefit from the inclusion of these details. -
Reviewer #2 (Public Review):
The authors aimed to explore the relationship between life course SES and BMI trajectories. They achieve the aim partially, and they could present the results more clearly. The work is interesting and will inform China's obesity public health programs and policies, but it is also interesting for other countries and communities. The exploration of life course exposures is relevant in many ways, and the authors did a good job conceptualizing the BMI and SES trajectories. However, some issues need to be improved, such as the discussions about bias and improvements in the writing and presentation of results.
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