Department of Public Health and Nursing, NTNU, Norwegian University of Science and Technology, Trondheim, Norway.
Centre for Fertility and Health & Centre for Disease Burden, Norwegian Institute of Public Health, Oslo, Norway.
BMC Health Serv Res. 2022 Mar 25;22(1):396. doi: 10.1186/s12913-022-07597-z.
Past studies have found associations between obesity and healthcare costs, however, these studies have suffered from bias due to omitted variables, reverse causality, and measurement error.
We used genetic variants related to body mass index (BMI) as instruments for BMI; thereby exploiting the natural randomization of genetic variants that occurs at conception. We used data on measured height and weight, genetic information, and sociodemographic factors from the Nord-Trøndelag Health Studies (HUNT), and individual-level registry data on healthcare costs, educational level, registration status, and biological relatives. We studied associations between BMI and general practitioner (GP)-, specialist-, and total healthcare costs in the Norwegian setting using instrumental variable (IV) regressions, and compared our findings with effect estimates from ordinary least squares (OLS) regressions. The sensitivity of our findings to underlying IV-assumptions was explored using two-sample Mendelian randomization methods, non-linear analyses, sex-, healthcare provider-, and age-specific analyses, within-family analyses, and outlier removal. We also conducted power calculations to assess the likelihood of detecting an effect given our sample 60,786 individuals.
We found that increased BMI resulted in significantly higher GP costs; however, the IV-based effect estimate was smaller than the OLS-based estimate. We found no evidence of an association between BMI and specialist or total healthcare costs.
Elevated BMI leads to higher GP costs, and more studies are needed to understand the causal mechanisms between BMI and specialist costs.
过去的研究发现肥胖与医疗保健成本之间存在关联，但这些研究受到了遗漏变量、反向因果关系和测量误差的影响，存在偏差。
我们使用与体重指数（BMI）相关的遗传变异作为 BMI 的工具；从而利用在受孕时发生的遗传变异的自然随机化。我们使用来自北特伦德拉格健康研究（HUNT）的测量身高和体重、遗传信息和社会人口因素的数据，以及关于医疗保健成本、教育水平、登记状况和生物学亲属的个人层面登记数据。我们使用工具变量（IV）回归研究了 BMI 与挪威普通医生（GP）、专科医生和总医疗保健成本之间的关联，并将我们的发现与普通最小二乘法（OLS）回归的效应估计进行了比较。我们使用两样本孟德尔随机化方法、非线性分析、按性别、医疗服务提供者和年龄划分的分析、家族内分析和异常值剔除，探讨了我们的发现对潜在 IV 假设的敏感性。我们还进行了功效计算，以评估在我们的 60786 名个体样本中检测到效应的可能性。
我们发现，BMI 升高与 GP 成本显著升高相关；然而，基于 IV 的效应估计值小于基于 OLS 的估计值。我们没有发现 BMI 与专科医生或总医疗保健成本之间存在关联的证据。
升高的 BMI 会导致 GP 成本增加，需要更多的研究来了解 BMI 与专科医生成本之间的因果机制。
