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Recent metformin adherence and the risk of hypoglycaemia in the year following intensification with a sulfonylurea

Min JY, Griffin MR, Chipman J, Hackstadt AJ, Greevy RA, Grijalva CG, Hung AM, Roumie CL

Diabetic medicine : a journal of the British Diabetic Association, 2019

187 participants

Abstract

AIM: To evaluate whether recent low adherence to metformin monotherapy is associated with hypoglycaemia after addition of a sulfonylurea.

METHODS: We assembled a retrospective cohort of veterans who filled a new prescription for metformin between 2001 and 2011 and intensified treatment with a sulfonylurea after ≥1 year of metformin use. We calculated metformin adherence from pharmacy data using the proportion of days covered in the 180-day period before intensification. The primary outcome was hypoglycaemia, defined as a hospitalization or emergency department visit for hypoglycaemia or an outpatient blood glucose measurement <3.3 mmol/l in the year following intensification. Cox proportional hazards models were used to compare the risk of hypoglycaemia between participants with low (<80%) and high (≥80%) adherence. Adherence was also modelled as a continuous variable using restricted cubic splines.

RESULTS: Of 187 267 participants who initiated metformin monotherapy, 49 424 added a sulfonylurea after ≥1 year. The median (interquartile range) rate of treatment adherence was 87 (50-100)% and 43% had adherence <80%. Hypoglycaemia rates per 1000 person-years were 23.1 (95% CI 21.1-25.4) and 24.5 (95% CI 22.7-26.4) in participants with low and high adherence, respectively (adjusted hazard ratio 0.95, 95% CI 0.84-1.08). The risk of hypoglycaemia was similar across all levels of adherence when adherence was modelled as a continuous variable.

CONCLUSIONS: We found no evidence that…

How strong is the evidence?

Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 187 participants or records.

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