Glycemic Control and Functional Decline in Nursing Home Residents With Diabetes

Type 1 and 2 diabetes increases the risk of dependence in activities of daily living (ADLs) in older adults.^1,2 However, stringent glycemic control in frail older adults may not improve physical function³ and can lead to adverse effects.⁴ Thus, we sought to determine the association between hemoglobin A_1c (HbA_1c) levels, persistent functional decline, and death in a national sample of nursing home residents.

Study participants were individuals 65 years or older who were admitted between January 1, 2005, and December 31, 2011, to 1 of 114 Veterans Affairs nursing homes with a diagnosis of type 1 or 2 diabetes as determined by International Classification of Diseases, Ninth Revision codes or an HbA_1c level higher than 6.5%. We excluded patients who were not receiving glucose-lowering medications.

Outcomes were death and persistent functional decline. Functional decline was determined using the Minimum Data Set (MDS)–ADL score, which accounts for 7 ADLs. Each ADL was scored from 0 to 4, where 0 indicates independence and 4 indicates total dependence, resulting in a summary score ranging from 0 to 28. Since functional status may fluctuate, we chose persistent functional decline as our outcome, defined as an increase in the MDS-ADL score of 2 points compared with the baseline score on 2 consecutive assessments.⁵

Our primary association was HbA_1c level on the day of the MDS-ADL assessment, determined through linear interpolation of HbA_1c measurements before and after the MDS-ADL assessment. Hemoglobin A_1c was categorized into the following 4 levels: 6.0% to 6.9%, 7.0% to 7.9%, 8.0% to 8.9%, and 9.0% or higher.

We accounted for potential confounders, including sex, age, baseline HbA_1c level, baseline MDS-ADL score, and comorbidities (congestive heart failure, cardiac arrhythmias, valvular heart disease, hypertension, peripheral vascular disease, chronic pulmonary diseases, cancer, hypothyroidism, liver disease, and paralysis). The unit of analysis was each resident’s first admission to a nursing home. We stratified results by the following types of glucose-lowering treatment: insulin, sulfonylureas (but no insulin), or other glucose-lowering medications (but no insulin or sulfonylureas).

Data analysis was performed from January 1, 2015, to August 20, 2016. We performed a Kaplan-Meier survival analysis, censoring for death or discharge of more than 30 days. We used Cox proportional hazards regression to estimate the hazard for functional decline, considering death as a competing risk using the method of Fine and Gray.⁶ We performed a sensitivity analysis, restricting our analysis to individuals with a nursing home stay of 6 months or more. This study was reviewed and approved by the University of California–San Francisco Committee on Human Research, who determined that individual patient consent was not required.

In our cohort of 7459 residents, the mean (SD) age was 76.0 (7.0) years, 7322 were male (98.2%), 3637 (48.8%) had a baseline HbA_1c level of 6.0% to 6.9%, 1264 (16.9%) had a baseline ADL score of 17 or more (suggesting the need for extensive assistance with most ADLs), and 5101 residents (68.4%) stayed in the nursing home for less than 6 months. There was no statistically significant difference among patients with the 4 levels of baseline HbA_1c in the percentage of individuals with functional decline or death during the 24 months of the study (Figure). Compared with the reference group (HbA_1c, 7.0%-7.9%), the adjusted hazard ratio for persistent functional decline considering death as a competing risk among those with a baseline HbA_1c level of 6.0% to 6.9% was 0.94 (95% CI, 0.80-1.10), while the adjusted hazard ratio for those with a baseline HbA_1c level of 9.0% or higher was 0.88 (95% CI, 0.65-1.18) (Table).⁷ Stratified results were similar, with no level of HbA_1c associated with persistent functional decline among residents taking insulin, sulfonylureas, or other glucose-lowering medications. Results were unchanged when restricting analysis to residents who stayed in the nursing home for 6 months or more.

In a national sample of Veterans Affairs nursing home residents with diabetes from 2005 to 2011, the degree of glycemic control was not associated with persistent functional decline or death during the 2 years of the study. Our results suggest that an HbA_1c level even greater than 9.0% may not increase the risk of persistent functional decline in nursing home residents with diabetes, suggesting that stringent glycemic control is not beneficial for these patients.

Corresponding Author: Sei J. Lee, MD, MAS, Division of Geriatrics, University of California, San Francisco, Medicine, 4150 Clement St, Bldg 1, Room 220F, San Francisco, CA 94121 (sei.lee@ucsf.edu).

Published Online: November 21, 2016. doi:10.1001/jamainternmed.2016.6949

Author Contributions: Drs Hsu and Lee had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Hsu, Lee.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Hsu.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: All authors.

Obtained funding: Lee.

Administrative, technical, or material support: Lee.

Conflict of Interest Disclosures: None reported.

Funding/Support: This work was conducted with support from the Paul Beeson Career Development Award K23AG040779 from the National Institute on Aging and the American Federation on Aging Research (Dr Lee). This work was also made possible with the support and facilities from the San Francisco Veterans Affairs Medical Center.

Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.