Epidemiologic patterns of biliary tract cancer in the United States: 2001-2015.

BACKGROUND: Biliary tract cancer (BTC) includes intrahepatic cholangiocarcinoma (ICC), extrahepatic cholangiocarcinoma, gallbladder cancer, and ampulla of Vater cancer (AVC). Although BTC is rare in the US, incidence is increasing and elevated in certain populations. This study examined BTC epidemiology in the US by age, sex, race/ethnicity, geographic region, and anatomic site. METHODS: BTC incidence, prevalence, mortality, and survival from 2001 to 2015 were evaluated using the National Cancer Institute's Surveillance, Epidemiology, and End Results Program and the Centers for Disease Control and Prevention's National Program of Cancer Registries databases. Incidence and mortality rates were calculated and reported as age-standardized rates. Data were assessed by age, anatomic sites, geographic region, and race/ethnicity, and a joinpoint regression model was used to predict trends for age-adjusted BTC incidence and mortality rates. RESULTS: BTC incidence increased during the study period (annual percent change = 1.76, 95% confidence interval [1.59-1.92]), with the highest increase in ICC (6.65 [6.11-7.19]). Incidence of unspecified BTC initially increased but has recently begun to drop. Hispanic, Asian/Pacific Islander, Black, or American Indian/Alaska Native race/ethnicity was associated with higher BTC mortality rates than White race/ethnicity. Patients with ICC had the highest mortality rate (age-standardized rate = 1.87/100,000 person-years [1.85-1.88]). Five-year survival was 15.2% for all BTC, ranging from 8.5% (ICC) to 34.5% (AVC), and patients with distant disease at diagnosis had lower survival (3%) compared with those with regional (19.1%) or locally advanced disease (31.5%). CONCLUSIONS: BTC incidence increased, survival was low across all subtypes, and mortality was greatest in patients with ICC. This underscores the serious, increasing unmet need among patients with BTC. Treatment options are limited, although clinical studies investigating immunotherapy, targeted therapies, and alternative chemotherapy combinations are ongoing. Epidemiological insights may improve patient care and inform the integration of novel therapies for BTC.

Real-world evidence on survival, adverse events, and health care burden in Medicare patients with mantle cell lymphoma.

Most data on overall survival (OS) and adverse events (AEs) in patients with mantle cell lymphoma (MCL) are from controlled trials; therefore, in this population-based study, we retrospectively assessed treatment patterns, OS, and AEs in MCL patients initiating systemic treatment during 2013-2015 using the United States Medicare claims database. Among 1390 eligible patients (median age = 74 years), chemoimmunotherapy with bendamustine/rituximab (BR) was the preferred choice in first-line (35.3%), followed by ibrutinib (33.5%), rituximab (9.1%), and rituximab/cyclophosphamide/doxorubicin/vincristine (R-CHOP) (6.8%). Twenty-four-month OS was 73% for BR; 47%, ibrutinib; 72%, rituximab; and 71%, R-CHOP. For the four most commonly used regimens, neutropenia, anemia, hypertension, and infection were the most frequent AEs. Patients with ≥3 AEs had nearly four times higher monthly costs than those with 0-2 AEs in the first observed therapy line. Findings demonstrate a substantial increase in the economic burden as the number of AEs increased among the Medicare MCL patients.

Overall survival, adverse events, and economic burden in patients with chronic lymphocytic leukemia receiving systemic therapy: Real-world evidence from the medicare population.

BACKGROUND: Information on overall survival (OS) and adverse events (AEs) in patients with chronic lymphocytic leukemia (CLL) is mostly available from clinical trials. We therefore conducted a population-based retrospective cohort study to assess OS, incidence of AEs, and economic burden in real-world practice among Medicare patients treated for CLL. METHODS: Patients with CLL receiving ≥1 systemic therapy from 2013 to 2015 were selected from the Medicare claims database and followed from the start of first observed systemic therapy (index date) through December 2016 or death. OS for patients receiving each of the most commonly observed treatments was estimated by the Kaplan-Meier method. AEs were assessed among patients receiving these treatments across all observed lines of therapy. All-cause direct medical costs were assessed from the Medicare system perspective. RESULTS: Among 7,965 eligible patients across all observed therapy lines, ibrutinib monotherapy (Ibr; n = 2,708), chlorambucil monotherapy (Clb; n = 1,620), and bendamustine/rituximab (BR; n = 1,485) were the most common treatments. For first observed therapy, 24-month OS estimates for Ibr, Clb, and BR recipients were 69% (95% CI = 68%-71%), 68% (95% CI = 65%-71%), and 79% (95% CI = 77%-81%) respectively. The most frequently recorded AEs in patients receiving these treatments in any observed line of therapy were neutropenia, hypertension, anemia, and infection. For all patients, the mean monthly all-cause cost during the follow-up period was $8,974 (SD = $11,562); cost increased by the number of AEs, from $5,144 (SD = $5,409) among those with 1-2 AEs to $10,077 (SD = $12,542) among those with ≥6 AEs. CONCLUSION: Over two-thirds of patients survived at least 2 years after starting their first observed therapy for CLL. Our findings highlight considerable susceptibility to AEs and unmet medical need in Medicare patients with CLL treated in routine practice. Medicare incurred substantial economic burden following initiation of systemic therapy, and patients with greater numbers of AEs accounted disproportionately for the high overall cost of CLL management.

Adverse Events and Economic Burden Among Patients Receiving Systemic Treatment for Mantle Cell Lymphoma: A Real-World Retrospective Cohort Study.

BACKGROUND/AIM: Limited published real-world data describe adverse events (AEs) among patients treated for mantle-cell lymphoma (MCL). The aim of this retrospective study was to describe treatment patterns, AEs, and associated healthcare costs. PATIENTS AND METHODS: Patients had two or more claims coded for MCL diagnosis, the first claim date (07/01/2012-05/31/2017) was the index date. Patients with pre-index MCL diagnosis or systemic treatment, or hematopoietic stem cell transplantation were excluded. Cohorts by regimen were followed for up to three lines of therapy. RESULTS: Patients (n=395; median age 72 years; 31% female) were observed over a total of 576 lines of therapy, the most common being bendamustine plus rituximab; rituximab monotherapy; R-CHOP; and ibrutinib. The most frequent AEs were hypertension (40.5%), anemia (37.7%), and infection (36.1%). However, hepatotoxicity ($19,645), stroke ($18,893), and renal failure ($9,037) were associated with the highest medical costs per patient per month. CONCLUSION: Among patients receiving common systemic treatments for MCL, AEs occurred frequently; some imposed substantial inpatient care costs.

Treatment patterns and outcomes among mantle cell lymphoma patients treated with ibrutinib in the United States: a retrospective electronic medical record database and chart review study.

The experience of patients with mantle cell lymphoma (MCL) in community oncology practices, including reasons for treatment discontinuation, is sparse. This retrospective study sought to elucidate treatment patterns and outcomes of patients with MCL treated with ibrutinib in the community setting. Patients were identified from the US Oncology Network electronic medical records database, iKnowMedTM , between 1 November 2013 and 31 October 2016. Descriptive analysis was performed to describe the demographic and clinical characteristics of the population. Kaplan-Meier estimates were performed to determine clinical outcomes. A Cox proportional hazards model was used to identify predictors of survival. Of the 1914 patients identified with MCL, 159 were treated with ibrutinib. The median age was 71 years and the majority were male (76%) and Caucasian (89%). The overall discontinuation rate was 83·6%; the most common reasons were progression (35%) and toxicities (25·6%). The median overall survival and progression-free survival was 25·82 months (95% confidence interval [CI] 19·94, NR) and 19·55 months (95% CI 16·52, 24·28) respectively. In multivariate modelling, patient age was predictive of survival (hazard ratio 1·041, P = 0·0186). Ibrutinib was temporarily reduced in 16·4% (n = 26) and held in 30·2% (n = 48), primarily due to toxicity 66·7% (n = 32). Survival data showed similarities between community oncology practices and clinical trials.

The economic burden of systemic lupus erythematosus in commercially- and medicaid-insured populations in the United States.

OBJECTIVE: To estimate the economic burden of systematic lupus erythematous (SLE), stratified by disease severity, in commercially- and Medicaid-insured US populations. METHODS: Adults (≥18 years) with SLE treated with antimalarials, selected biologics, immunosuppressants, and systemic glucocorticoids (2010-2014) were identified within the commercial and Medicaid insurance IBM MarketScan® databases (index date = first SLE medication claim). Both cohorts were stratified into mild (receiving antimalarial or glucocorticoid monotherapy ≤5 mg/day) versus moderate/severe SLE (receiving glucocorticoids >5 mg/day, biologic, immunosuppressant, or combination therapy) during a 6-month exposure period. All-cause healthcare utilization and costs were evaluated during the 12 months following the exposure period. RESULTS: Among 8231 commercially-insured patients, 32.6% had mild and 67.4% had moderate/severe SLE by our definition. Among 802 Medicaid-insured patients, 25.2% had mild and 74.8% had moderate/severe SLE. Adjusted mean total healthcare costs, excluding pharmacy, for moderate/severe SLE patients were higher than for mild SLE patients in the commercially-insured ($39,021 versus $23,519; p < 0.0001) and Medicaid-insured populations ($56,050 versus $44,932; p = 0.06). In both SLE severity populations total unadjusted costs were significantly higher among Medicaid-insured than commercially-insured patients. CONCLUSION: Commercially-insured patients with treatment suggesting moderate/severe SLE incurred significantly higher adjusted mean healthcare costs, excluding pharmacy, compared with mild SLE patients. While not reaching statistical significance, moderate/severe Medicaid-insured patients had higher costs then mild SLE patients. Total unadjusted healthcare costs were significantly higher among Medicaid-insured than commercially-insured patients. These differential costs are important to consider and monitor when implementing interventions to improve health and reduce healthcare spending for SLE.

Correction to: Real-World Treatment Patterns, Adverse Events, Resource Use, and Costs Among Commercially Insured, Younger Patients with Chronic Lymphocytic Leukemia in the USA: A Retrospective Cohort Study.

In the original article, it has been noticed that the abbreviation ''CLL'' is incorrectly published throughout the paper as the abbreviation "CCL". The correct abbreviation is "CLL".

Real-World Treatment Patterns, Adverse Events, Resource Use, and Costs Among Commercially Insured, Younger Patients with Chronic Lymphocytic Leukemia in the USA: A Retrospective Cohort Study.

INTRODUCTION: Amidst a changing treatment landscape, real-world evidence on the burden of chronic lymphocytic leukemia (CLL) is limited. The purpose of this study was to describe treatment patterns, adverse events (AEs), and economic burden among treated patients with CLL. METHODS: A retrospective cohort study was conducted with IQVIA PharMetrics® Plus. Patients at least 18 years old with CLL treatment between November 1, 2013 and May 31, 2018 were identified; index date was first observed CLL treatment. Patients had at least one CLL diagnosis pre-index and a second diagnosis anytime during the study period, at least 1-year pre- and at least 30-day post-index continuous enrollment and no pre-index CLL treatment. Analyses focused on patients receiving one of the four most common regimens observed. Outcomes included treatment patterns, frequency of incident AEs, and healthcare resource use and costs. Multivariable logistic regression and generalized linear modelling were used to evaluate risk of hospitalization and all-cause costs per patient per month (PPPM). RESULTS: A total of 1706 patients were included in the study (median [interquartile range] age 58 [55-62] years, 66% male, median Charlson Comorbidity Index 2 [2-3], median follow-up 16 [8-28] months). Common regimens, irrespective of treatment line, were bendamustine-rituximab (B-R, 27%), ibrutinib monotherapy (I, 27%), rituximab monotherapy (R, 19%), and fludarabine combined with cyclophosphamide and rituximab (FCR, 16%); 59% had at least one incident AE (B-R, 62%; I, 60%; R, 25%; FCR, 79%). Mean total all-cause healthcare cost over follow-up was $13,858 ± 14,626 PPPM. Increased number of AEs was associated with increased odds of hospitalization (odds ratio = 2.9; 95% confidence interval [CI] 2.5-3.4) and increased mean cost PPPM (cost ratio = 1.2; 95% CI 1.1-1.2). CONCLUSION: This study highlights the treatment toxicity and associated economic burden among patients with CLL in the USA. As novel therapies are increasingly used, further research examining outcomes will inform the risks, benefits, and value of novel agents to prescribers and patients.

Adverse event rates and economic burden associated with purine nucleoside analogs in patients with hairy cell leukemia: a US population-retrospective claims analysis.

BACKGROUND: Purine nucleoside analogs (PNAs) are the recommended first-line treatment for patients with hairy cell leukemia (HCL), but they are associated with adverse events (AEs). Due to a lack of real-world evidence regarding AEs that are associated with PNAs, we used commercial data to assess AE rates, AE-related health care resource utilization (HCRU), and costs among PNA-treated patients with HCL. Adults aged ≥18 years with ≥2 claims for HCL ≥30 days apart from 1 January 2006 through 31 December 2015 were included. Included patients had ≥1 claim for HCL therapy (cladribine ± rituximab or pentostatin ± rituximab [index date: first claim date]) and continuous enrollment for a ≥ 6-month baseline and ≥ 12-month follow-up period. Patient sub-cohorts were based on the occurrence of myelosuppression and opportunistic infections (OIs). Generalized linear models were used to compare HCRU and costs. RESULTS: In total, 647 PNA-treated patients were identified (mean age: 57.1 years). Myelosuppression and OI incidence were 461 and 42 per 1000 patient-years, respectively. Adjusted results indicated that those with myelosuppression had higher rates of hospitalization (47.4% vs 12.4%; P < .0001) and incurred higher mean inpatient costs ($23,517 vs $12,729; P = .011) and total costs ($57,325 vs $34,733; P = .001) as compared with those without myelosuppression. Similarly, patients with OIs had higher rates of hospitalization (53.8% vs 30.8%; P = .025) and incurred higher mean inpatient costs ($21,494 vs $11,229; P < .0001) as compared with those without OIs. CONCLUSIONS: PNA therapy is highly effective but associated with significant toxicities that increase costs; these findings indicate a need for therapies with improved toxicity profiles and better risk stratification of patients at risk of developing myelosuppression and OIs.

Matching-adjusted Indirect Comparisons of the Efficacy and Safety of Acalabrutinib Versus Other Targeted Therapies in Relapsed/Refractory Mantle Cell Lymphoma.

PURPOSE: Mantle cell lymphoma (MCL) is a rare subtype of B-cell non-Hodgkin lymphoma that can be either aggressive or indolent. Although MCL usually responds well to initial treatment with chemotherapy-based regimens, the disease often relapses or becomes refractory within a few years. Acalabrutinib is a highly selective, potent, covalent Bruton tyrosine kinase inhibitor with minimal off-target activity. WIthout head-to-head clinical trial data, estimation of the comparative efficacy and safety of new therapeutic entities provides valuable information for patients, clinicians, and health care payers. The objective of this analysis was to compare the efficacy and safety of acalabrutinib versus other targeted therapies employed for the treatment of relapsed/refractory MCL by using matching-adjusted indirect comparisons. METHODS: Individual data from 124 patients treated with acalabrutinib in the Phase II ACE-LY-004 trial were adjusted to match average baseline characteristics of populations from studies using alternative targeted treatment regimens for relapsed/refractory MCL (for monotherapy: ibrutinib, bortezomib, lenalidomide, and temsirolimus; for combination therapies: ibrutinib + rituximab, bendamustine + rituximab, and lenalidomide + rituximab). Patient populations were matched on age, sex, race, Eastern Cooperative Oncology Group performance status, Simplified MCL International Prognostic Index score, tumor bulk, lactate dehydrogenase concentration, extranodal disease, bone marrow involvement, and number of previous treatment regimens. Outcomes assessed included overall response rate (ORR), complete response (CR) rate, overall survival (OS), progression-free survival (PFS), and adverse events. FINDINGS: After matching, acalabrutinib was associated with significant increases in ORR and CR rate (estimated treatment difference [95% CI]) versus ibrutinib (ORR, 9.3% [0.3-18.3]; CR, 14.9% [5.4-24.3]), bortezomib (ORR, 50.6% [40.2-61.0]; CR, 18.8% [9.1-28.5]), lenalidomide (ORR, 38.1% [27.1-49.1]; CR, 43.5% [34.8-52.3]), and temsirolimus (ORR, 40.7% [31.0-50.4]; CR, 27.1% [19.2-35.0]). PFS (hazard ratio [95% CI]) with acalabrutinib was significantly increased versus bortezomib (0.36 [0.26-0.51]), lenalidomide (0.65 [0.48-0.89]), lenalidomide + rituximab (0.57 [0.35-0.93]), and temsirolimus (0.33 [0.24-0.45]). Acalabrutinib was associated with significantly increased OS (hazard ratio) versus bortezomib (0.36 [0.22-0.61]) and temsirolimus (0.32 [0.23-0.44]). The overall safety profile of acalabrutinib was similar or better compared with the monotherapies; however, infection risk increased versus bendamustine + rituximab, and anemia increased risk versus lenalidomide + rituximab and ibrutinib + rituximab. IMPLICATIONS: This comparison of targeted therapies used in the treatment of relapsed/refractory MCL showed that acalabrutinib has the potential to provide increased response rates, with trends for increased PFS and OS, and an improved safety profile.

Treatment patterns, adverse events, healthcare resource use and costs among commercially insured patients with mantle cell lymphoma in the United States.

INTRODUCTION: There are limited data on treatment patterns, adverse events (AEs), and economic burden in younger, commercially insured patients treated for mantle cell lymphoma (MCL). METHODS: Adults with ≥1 treatment for MCL between 1 November 2013-31 December 2017 were identified from IQVIA Real-World Data Adjudicated Claims-US; index date was first treatment. Patients carried ≥1 MCL diagnosis, were newly treated, and were enrolled continuously for ≥12 months prior to and ≥30 days following index. Patients receiving the four most common MCL regimens were included. Measures included frequency of incident AEs, resource use, and costs overall and by number of AEs. Adjusted logistic regression and generalized linear modeling evaluated risk of hospitalization and all-cause costs per patient per month (PPPM). RESULTS: Two thousand five hundred and nine treated patients had a drug-specific code and were classified to a specific treatment regimen. Of those patients, 1785 patients received at least one of the four most commonly used MCL regimens (R-CHOP, rituximab monotherapy, B-R, and ibrutinib) at some point over follow-up (median 23 months). R-CHOP was the most common regimen observed in the first line (26%), followed by rituximab monotherapy (19%), B-R (15%), and ibrutinib (5%). The median age was 57 years; median Charlson Comorbidity Index was 0. Among patients receiving the four most common regimens, 63% of patients experienced ≥1 incident AE (R-CHOP 77%, B-R 58%, and ibrutinib 52%). An increasing number of incident AEs was associated with increased hospitalization risk (odds ratio = 2.4; 95% Confidence Interval [CI] 2.1-2.7) and increased mean costs PPPM (cost ratio = 1.1; 95% CI 1.1-1.2). DISCUSSION: This is the largest study describing treatment patterns and clinical and economic impact of MCL treatment. The most common regimens were R-CHOP, rituximab monotherapy, B-R, and ibrutinib. The majority of treated patients experienced at least one incident AE, with hospitalization risk and all-cause costs increasing as the number of AEs increased.

Treatment patterns, adverse events, and economic burden in a privately insured population of patients with chronic lymphocytic leukemia in the United States.

INTRODUCTION: Contemporary data describing treatment patterns, adverse events (AEs), and outcomes in patients with chronic lymphocytic leukemia (CLL) in clinical practice are lacking. We conducted a retrospective cohort study and assessed treatment patterns, AEs, health-care resource use (HCRU), and costs in patients with diagnosis of CLL. METHODS: Using a nationally representative population of privately insured patients in the US, adult patients with CLL diagnosis (July 2012-June 2015) were selected if they had continuous health plan enrollment for ≥12 months before the first CLL diagnosis without any evidence of any CLL-directed treatment. Treatment patterns up to four lines of therapy (LOT) and occurrence of AEs during CLL therapies were assessed. Mean per-patient monthly HCRU and costs were assessed overall and by number of unique AEs. RESULTS: Of all patients meeting the selection criteria (n = 7,639; median age, 66 years), 18% (n = 1,379) received a systemic therapy during study follow-up. Of these, bendamustine/rituximab (BR) was the most common first observed regimen (28.1%), while ibrutinib was the most common therapy in the second (20.8%) and third (25.5%) observed regimens. The mean monthly all-cause and CLL-related costs, among patients treated with a systemic therapy, were $7,943 (SD = $15,757) and $5,185 (SD = $9,935), respectively. Mean monthly all-cause costs increased by the number of AEs (from $905 [SD = $1,865] among those with no AEs to $6,032 [SD = $13,290] among those with ≥6 AEs). CONCLUSIONS: Chemoimmunotherapy, particularly BR, was the most common first observed therapy for CLL, whereas ibrutinib was most preferred in the second and third observed lines of therapy during the study period. Findings demonstrate that the economic burden of AEs in CLL is substantial.

Adverse events, resource use, and economic burden associated with mantle cell lymphoma: a real-world assessment of privately insured patients in the United States.

In view of recent therapeutic advances in mantle cell lymphoma (MCL), the aim of this retrospective cohort analysis was to assess treatment patterns, adverse events (AEs), resource utilization, and health care costs in patients with MCL in a US-based commercial claims database. A total of 783 patients with MCL (median age = 65 years) were selected. Among patients receiving systemic therapy (n = 457), the most common treatment regimens were bendamustine/rituximab (BR) (41.1%), rituximab/cyclophosphamide/doxorubicin/vincristine (RCHOP) (26.7%), rituximab monotherapy (20.4%), and ibrutinib monotherapy (14.2%). Mean monthly costs during treatments with BR, RCHOP, rituximab, and ibrutinib were $12,958, $24,719, $13,153, and $21,690, respectively. Mean monthly cost during follow-up was $13,650 among patients with ≥6 AEs versus $5131 among those without AEs. The costs of MCL varied considerably by treatment regimen and care setting. The overall economic burden of managing patients with MCL can be substantially affected by costs associated with managing AEs occurring during treatment.

Multivariate path analysis of serum 25-hydroxyvitamin D concentration, inflammation, and risk of type 2 diabetes mellitus.

BACKGROUND AND AIMS: Despite growing interest in the protective role that vitamin D may have in health outcomes, little research has examined the mechanisms underlying this role. This study aimed to test two hypotheses: (1) serum 25-hydroxyvitamin D [25(OH)D] is inversely associated with type 2 diabetes mellitus (T2DM) and elevated hemoglobin A1c; (2) these associations are mediated by serum C-reactive protein (CRP). METHODS: Participants aged 20 and older in 2001-2006 National Health and Nutrition Examination Surveys (n = 8,655) with measures of serum 25(OH)D, CRP, hemoglobin A1c, and other important covariates were included in the present study. Logistic regression and path analysis methods were applied to test the study hypotheses. RESULTS: Decreased serum 25(OH)D concentration was significantly associated with increased odds of T2DM. In males, an estimated 14.9% of the association between 25(OH)D and hemoglobin A1c was mediated by serum CRP. However, this mediation effect was not observed in females. CONCLUSION: Using a nationally representative sample, the present study extends previous research and provides new evidence that the effect of decreased serum vitamin D concentration on T2DM may proceed through increased systemic inflammation in males. Longitudinal studies and randomized control trials are needed to confirm the present findings.

Joint effects of obesity and vitamin D insufficiency on insulin resistance and type 2 diabetes: results from the NHANES 2001-2006.

OBJECTIVE: The possible interaction of serum 25-hydroxyvitamin D [25(OH)D] and obesity in regard to type 2 diabetes and insulin resistance has not been well studied. To explore the effect modification of obesity on the association between 25(OH)D and insulin resistance/type 2 diabetes, data were examined from a nationally representative sample. RESEARCH DESIGN AND METHODS: The analytic sample for the type 2 diabetes analysis (n = 12,900) was limited to participants from the National Health and Nutrition Examination Survey (NHANES) 2001-2006 over 20 years of age. Participants >20 years of age assigned to the morning session and free of diabetes were limited to the insulin resistance analysis (n = 5,806). Multiplicative interaction was assessed through a cross-product interaction term in a multiple logistic regression model. The presence of additive interaction between insufficient 25(OH)D and obesity (indicated by BMI or waist circumference) was evaluated by calculation of the relative excess risk due to interaction (RERI) and attributable proportion due to interaction (AP). RESULTS: There was no multiplicative interaction of insufficient 25(OH)D and obesity on type 2 diabetes or insulin resistance. Furthermore, none of the RERI or AP values were statistically significant in the diabetes analysis. However, there was strong additive interaction between abdominal obesity and insufficient 25(OH)D (RERI 6.45 [95% CI 1.03-11.52]) in regard to insulin resistance. In addition, 47% of the increased odds of insulin resistance can be explained by interaction between insufficient 25(OH)D and high BMI (AP 0.47 [95% CI 0.08-0.87]). CONCLUSIONS: Within a cross-sectional, nationally representative sample, abdominal obesity and insufficient 25(OH)D interact to synergistically influence the risk of insulin resistance.