The impact of mental health on outcome after anterior cervical discectomy: cohort study assessing the influence of mental health using predictive modelling

Abstract

Background: Depression and anxiety are common mental disorders among patients with chronic pain. It is hypothesised that patients suffering from these disorders benefit less from cervical spine surgery than mentally healthy patients. Therefore, this study aimed to quantify the effect of mental health status on functional outcome after anterior cervical discectomy in a post hoc analysis on RCT data.

Methods: One hundred eight patients from the NECK trial, with radiculopathy due to a one-level herniated disc, underwent anterior cervical discectomy and were included into this analysis. Functional outcome was quantified using the Neck Disability Index (NDI), and mental health status was measured using the Hospital Anxiety and Depression Score (HADS) questionnaire. NDI differences were assessed using generalised estimated equations (GEE), crude means, a predictive linear mixed model (LMM) using baseline scores and over time with an explanatory LMM.

Results: At baseline, 24% and 32% of patients were respectively depressed and anxious and had statistically significant and clinically relevant higher NDI scores during follow-up. However, in those patients in which the HADS returned to normal during follow-up, NDI values decreased comparably to the non-depression or non-anxiety cases. Those patients that demonstrated persisting high HADS values had convincingly worse NDI scores. A predictive LMM showed that combining baseline NDI and HADS scores was highly predictive of NDI during follow-up. The R shiny application enabled the effective, visual communication of results from the predictive LMM.

Conclusion: This study shows that mental health status and disability are strongly associated and provides insight into the size of the effect, as well as a way to use this relation to improve preoperative patient counselling. These findings give rise to the suggestion that incorporating mental health screening in the preoperative assessment of patients could help to adequately manage patients' expectations for functional recovery.

Trial registration: Dutch Trial Register Number: NTR1289.

Keywords: Anxiety; Cervical discectomy; Cervical radiculopathy; Depression; Mental health; Neck disability index; Outcome prediction; Radicular pain.

Fig. 1

Flow chart illustrating the inclusion process

Fig. 2

NDI during follow-up for each HADS depression group. HADS depression groups are based on the baseline HADS scores reported

Fig. 3

NDI during follow-up for each HADS anxiety group. HADS anxiety groups are based on the baseline HADS scores reported

Fig. 4

5-fold cross-validation (CV) with the predictions (in red) and actual NDI (in dark grey) of one fold. The x-axis visualises the specific anonymized patient ID combined with a visit (52 or 104 weeks). For CV, the data is randomly divided into 5 parts, where 4 parts will function as the training data and the 5th part as the test data. The procedure is repeated 5 times. The lower the root mean square error (RMSE), the better the predictive ability of the model, and the RMSE can also be interpreted as the average amount of NDI points that the model predicts less or more than the actual NDI

Fig. 5

Predicted NDI values on weeks 52 and 104 and their confidence intervals for four individual patients are shown in colour. The black lines are the true NDI values. In the patient-specific predictions, the training data is created by removing one patient from the dataset. The predictive LMM is trained on this training data and predicts for the left out patient. This procedure is repeated four times, for four different patients

Fig. 6

Screenshots of the R shiny application illustrating how it functions. On the left, the input can be given, and on the right, the predicted NDIs will be visualised in the graph (red line). On the left side, the adjustable baseline measurements for NDI, HADS anxiety and HADS depression. On the right, the graph visualising (red line) the predicted NDI on the y-axis during the follow-up moment in weeks on the x-axis, and the marginal mean NDI (blue line) over time with a 95% confidence interval (in grey). Beneath the graph, the numerical values appear for the predicted NDI at weeks 52 and 104

Fig. 7

Marginal NDI over time (in blue) with a 95% confidence interval (dark grey). The NDI of individual subjects is plotted in the background

Fig. 8

NDI during follow-up for the delta NDI groups. Patients were grouped based on their HADS score over time