Anxiety, depression and timing of insulin treatment among people with type 2 diabetes: Nine-year follow-up of the Nord-Trondelag Health Study, Norway

Background
Depression and anxiety have been found to be predictors of poor health outcomes in diabetes, but mechanisms are still unclear.
Aims
To examine whether symptoms of anxiety and depression were associated with timing of initiating insulin therapy.
Methods
A cohort study of insulin-naive particpants with type 2 dabetes completed the Hospital Anxiey and Depression Scale, HADS-A (n = 731) and/or the HADS-D (n = 768) in the communy-based Nord-Trøndelag Health Study (1995-1997). Information on insulin initiation was retrieved from the Norwegian Prescription Database from January 1, 2004 to November 21, 2012. Cox regression analyses were used to estimate the association between symptoms of anxiety, depression and time to insulin initiation.
Results
At baseline, 19% reported anxiety symptoms (score ≥ 8) and 18% depressive symptoms (score ≥ 8). After a mean follow-up of 4.4 (SD 3.6) years, 337 (40%) participants had started insulin therapy. After adjustment for sociodemographic and clinical variables, anxiety symptoms were associated with later initiation of insulin therapy (HR 0.70, 95% CI 0.49–0.99), while depressive symptoms were not. Considering groups simultaneously, having both elevated depressive and elevated anxiety symptoms was associated with later time to insulin initiation (HR 0.62, 95% CI 0.39–0.99), while having only anxiety symptoms (without depressive) HR 0.81, 95% CI 0.50–1.32) or only depressive symptoms (without anxiety) (HR 1.08, 95% CI 0.68–1.72) were not.
Conclusions
Anxiety was associated with a later initiation of insulin, while depressive symptoms were not. Persons with both elevated levels of anxiety and depression were also less likely to start insulin therapy. These results need further testing in other prospective studies.
Keywords: Anxiety, Depression, Insulin therapy, Insulin-naive people, Type 2 diabetes, Prospective study