Real-world costs of obesity-related complications over eight years: a US retrospective cohort study in 28,500 individuals

The study addresses how the burden of obesity-related complications (ORCs)—in terms of both number and type—affects total healthcare costs over time among adults with obesity in the USA. With obesity prevalence rising (over 40% of US adults in 2017–2018 and projected ~50% by 2030), associated comorbidities (e.g., hypertension, dyslipidemia, type 2 diabetes, osteoarthritis) impose substantial economic burden. Prior estimates indicate significant national medical expenditures attributable to obesity. However, many earlier cost studies were limited by regional data, short follow-up, or limited generalizability. This study aims to use large, linked national databases to quantify long-term cost trajectories by ORC burden, informing targeted prevention and management strategies to mitigate healthcare spending.

Previous US studies quantified ORC costs but had limitations. Li et al. (2015) using a primarily White regional EHR database found hypertension, dyslipidemia, and osteoarthritis as the costliest ORCs in people with obesity, each exceeding $23 million annual incremental costs per 100,000 versus those without comorbidity; generalizability was limited. Divino et al. (2021), using linked EHR-claims data, assessed 13 ORCs over mainly 1 year (max 3 years), finding osteoarthritis of the knee and heart failure with preserved ejection fraction as highest-cost ORCs, with mean 1-year complication-specific costs $3719–$4581 (OA knee) and $2585–$4648 (HFpEF) for people with obesity. The limited follow-up in prior work underscores the need for long-term, nationally representative cost trajectories by ORC count/type.

Design: Retrospective cohort study using linked IQVIA Ambulatory Electronic Medical Records (AEMR) and IQVIA PharMetrics Plus claims. Population: Adults ≥18 years with BMI 30.0–<70.0 kg/m² recorded between Jan 1, 2007 and Mar 31, 2012 (index date), with continuous enrollment ≥1 year pre-index (baseline) and ≥8 years post-index (follow-up). Study period spanned Jan 1, 2006 to Mar 31, 2020. Exclusions: Pre-index evidence of same/higher obesity class (BMI values or diagnosis codes), invalid/missing key variables (age, sex, region, year of cost, enrollment dates), pregnancy in baseline year, any cancer diagnosis (except non-melanoma skin cancer) during continuous pre-index enrollment, enrollment in Medicare cost or SCHIP plans, and implausible BMI changes (>20% within 30 days or >20% average monthly for measurements ≥30 days apart). ORC ascertainment: ORCs identified during baseline via ICD-9-CM/ICD-10-CM in PharMetrics Plus. ORCs: obstructive sleep apnea, heart failure, urinary incontinence, osteoarthritis (knee), type 2 diabetes (T2D), prediabetes, asthma, amaurosis, gastro-oesophageal reflux disease, hypertension, dyslipidemia, musculoskeletal pain, chronic kidney disease (including kidney failure), and atherothrombotic cardiovascular disease (ASCVD; cerebrovascular disease, ischemic heart disease, peripheral artery disease). Additional groups: Established CVD (ASCVD, HF, cardiomyopathies, DVT/PE, cardiac arrest, atrial fibrillation/flutter, atherosclerosis); high CV risk defined as ≥2 of hypertension, dyslipidemia, and T2D/prediabetes. Outcomes: Primary—total direct per-person healthcare costs (payer + patient out-of-pocket) at baseline and each follow-up year, converted to 2019 USD via CPI. Components: inpatient hospitalization, outpatient care, emergency department, and other outpatient medical; drug costs also summarized descriptively in figures. Costs calculated per person and averaged across years; cohorts stratified by presence/absence and number of ORCs. Statistical analysis: Reported observed and adjusted costs. Adjusted costs estimated via generalized estimating equations with gamma distribution and log link to predict total amounts at years 1–8 by cohort, adjusting for factors including age group, sex, region, year of cost, and obesity class; specific ORC presence (0 vs 1, ≥2 vs 1/0) included. Charlson Comorbidity Index, pre-index cost, and other ORCs were not included due to collinearity. Analyses in SAS 9.4. Ethical considerations: Use of fully de-identified data; not considered human subjects research.

- Cohort: 28,583 adults with obesity; at index: class I 62.6% (n=17,892), class II 22.9% (n=6,550), class III 14.5% (n=4,141). Baseline ORC count: 0 ORCs 44.4% (n=12,686); 1 ORC 25.3% (n=7,242); 2 ORCs 14.6% (n=4,180); ≥3 ORCs 15.7% (n=4,475). In ≥2 ORCs groups, most prevalent ORCs: hypertension (67.5% and 81.7%), musculoskeletal pain (53.1% and 59.8%), dyslipidemia (51.7% and 65.9%). - Costs by number of ORCs (adjusted mean annual, averaged over 8 years): 0 ORCs $5,149; 1 ORC $7,758; 2 ORCs $9,927; ≥3 ORCs $16,451 (Fig. 1a). Costs increased with ORC count. - Annual trajectory (all-cause per-person adjusted costs by follow-up year): Year 1 $15,585; Year 2 $9,483; Year 3 $7,718; Year 4 $11,819; Year 5 $20,349; Year 6 $9,000; Year 7 $8,926; Year 8 $511 (Fig. 1b). - Specific ORCs: Costs generally increased from year 1 to year 8; largest percentage increases: CKD +78.8%; T2D +47.8%. - Outpatient costs were the largest contributor to baseline annual direct costs and remained a major driver across years and ORC groups. - Stratified mean annual costs over 8 years by ORC presence (reported): With T2D $7,374 vs Without T2D $17,286; With established CVD $7,573 vs Without $17,070; With HF $8,141 vs Without $25,102; With CKD $8,072 vs Without $36,923; With OA knee $8,009 vs Without $16,129; High CV risk (≥2 risk factors) $7,079 vs Without high CV risk $14,334 (Fig. 2). - Costs increased across obesity classes, but within a given specific ORC, costs were generally similar across obesity classes.

The study demonstrates that comorbidity burden among adults with obesity is high and strongly associated with escalating healthcare costs over time. More than half had ≥1 ORC at baseline, and greater numbers of ORCs corresponded to higher adjusted mean annual total costs across the 8-year follow-up. For specific ORCs, costs rose over time, notably for CKD and T2D, indicating progressive resource use as complications advance. Outpatient care emerged as the main cost driver, suggesting intensive ambulatory management may reduce inpatient utilization but sustains substantial ongoing expenditures. High cardiovascular risk (≥2 of hypertension, dyslipidemia, T2D/prediabetes) was associated with elevated long-term costs comparable to T2D, highlighting the economic impact of clustered risk factors even before overt disease progression. While costs tended to increase with higher obesity class, within a specific ORC costs were similar across classes, implying that the accumulation of multiple ORCs, likely influenced by higher BMI, is a principal driver of overall costs. These findings underscore the importance of early identification and management of ORCs and cardiometabolic risk in obesity to mitigate long-term healthcare costs.

In a large, US-wide cohort of commercially insured adults with obesity followed for eight years, total healthcare costs increased with the number of obesity-related complications and rose over time for specific ORCs, especially CKD and T2D. Outpatient care was the predominant cost component. The accumulation of ORCs, rather than obesity class alone within a given ORC, appears to drive higher expenditures. These results support prioritizing prevention, early intervention, and comprehensive management of multiple cardiometabolic risk factors in people with obesity to curb long-term costs. Future research should evaluate cost trajectories and intervention impacts in underrepresented populations (e.g., uninsured, Medicare/Medicaid), incorporate ORC severity and socioeconomic factors, and assess strategies that may shift care to lower-cost settings without compromising outcomes.

Findings derive from commercially insured individuals with recorded BMI, limiting generalizability to uninsured or Medicare/Medicaid populations and other countries. Continuous enrollment requirements may introduce selection bias toward healthier, employed individuals who survived the follow-up. Index-year interactions with the insurance system likely contributed to elevated year-1 costs followed by reductions. Data lacked measures of ORC severity, lifestyle factors, socioeconomic status, and education, limiting adjustment for these confounders. Race/ethnicity distributions were balanced across ORC cohorts, reducing concern about confounding by ethnicity. Some participants may have undiagnosed early cancers associated with obesity, potentially underestimating related costs. Additional research is needed in elderly commercial insurance enrollees and fee-for-service Medicare/Medicaid populations.