The bidirectional longitudinal association between depressive symptoms and HbA_1c : A systematic review and...

To investigate whether there is a bidirectional longitudinal association of depression with HbA_1c .

We conducted a systematic literature search in PubMed, PsycINFO, CINAHL and EMBASE for observational, longitudinal studies published from January 2000 to September 2020, assessing the association between depression and HbA_1c in adults. We assessed study quality with the Newcastle-Ottawa-Scale. Pooled effect estimates were reported as partial correlation coefficients (r_p ) or odds ratios (OR).

We retrieved 1642 studies; 26 studies were included in the systematic review and eleven in the meta-analysis. Most studies (16/26) focused on type 2 diabetes. Study quality was rated as good (n = 19), fair (n = 2) and poor (n = 5). Of the meta-analysed studies, six investigated the longitudinal association between self-reported depressive symptoms and HbA_1c and five the reverse longitudinal association, with a combined sample size of n = 48,793 and a mean follow-up of 2 years. Higher levels of baseline depressive symptoms were associated with subsequent higher levels of HbA_1c (partial r = 0.07; [95% CI 0.03, 0.12]; I² 38%). Higher baseline HbA_1c values were also associated with 18% increased risk of (probable) depression (OR = 1.18; [95% CI 1.12,1.25]; I² 0.0%).

Our findings support a bidirectional longitudinal association between depressive symptoms and HbA_1c . However, the observed effect sizes were small and future research in large-scale longitudinal studies is needed to confirm this association. Future studies should investigate the role of type of diabetes and depression, diabetes distress and diabetes self-management behaviours. Our results may have clinical implications, as depressive symptoms and HbA_1c levels could be targeted concurrently in the prevention and treatment of diabetes and depression.

PROSPERO ID CRD42019147551.