The CIPD published its 24th Health and Wellbeing at Work survey in September 2025, and the headline figure has not had the attention it deserves. The average UK employee now takes 9.4 days of sickness absence per year, the highest level recorded in more than fifteen years. The figure was 7.8 days in 2023 and 5.8 days in 2022. The line is not flattening, it is climbing.
The cause is named clearly in the data. Mental ill health is the leading cause of long-term absence and the second most common cause of short-term absence, behind minor illness. The CIPD also finds that only 29% of organisations train line managers in mental health. Where managers are trained, 73% of those organisations report managers feel confident having sensitive discussions and signposting support. The capability swing between trained and untrained is the most actionable number in the report.
Three numbers, one shape. Absence is at a 15-year peak. Mental ill health is the main driver. Seven in ten organisations have not given their managers any training in the conversation that would catch the early signal. The cost shows up in days. The cause shows up in conversations that did not happen.
Why The Absence Number Is A Behaviour Number
The temptation, looking at 9.4 days, is to treat it as a wellbeing-policy problem. More EAP coverage. A new mental-health-awareness week. An additional line in the handbook. None of those are wrong. None of them are the primary lever, because none of them act at the point the absence is decided.
The point the absence is decided is the conversation in the corridor, in the one-to-one, on the Teams call, when the manager has 90 seconds to react to a colleague saying "I'm fine" in a voice that is not fine. What happens in those 90 seconds predicts whether the next month ends with a quiet check-in or a fit note. Amy Edmondson's 1999 work in Administrative Science Quarterly on psychological safety identifies the manager's opening behaviour as the strongest predictor of whether the team will surface a problem early. The CIPD's own data shows the same thing from the other side: where managers are trained, the proportion who can have the sensitive conversation jumps to 73%. Where they are not, organisations are guessing.
What Most Organisations Try, And Why It Misses
The standard response to the 9.4 days is to lift inputs. More e-learning. A new wellbeing platform. Mental Health First Aider badges. The evidence is unkind to all three as primary interventions, for the same retention reason that turns up in every L&D conversation. Roediger and Karpicke (2006), in Psychological Science, established that active retrieval improves long-term retention by around 50% compared with passive review. A 45-minute mental-health-awareness module sits firmly on the wrong side of that curve. A manager who completes the module has, three months later, done the cognitive equivalent of skimming a chapter. When the actual corridor moment arrives, they do not have a sentence ready.
This is the gap between the 29% and the 73%. The 29% is the proportion of organisations who train managers. The 73% is the proportion of those trained managers who can run the conversation confidently. The lever is not awareness, it is rehearsed, observable behaviour. CIPD's data implicitly says the same thing: training works, only a minority of UK organisations actually do it, and the format of the training is decisive.
What The Conversation Actually Looks Like
The corridor version of this conversation is short. A team member says "I'm fine" in a tone that contradicts the words, or volunteers a flat "things at home are a bit much at the moment". The 90 seconds that follow determine whether the early signal becomes an early intervention or a delayed absence. Three observable behaviours predict the good outcome.
- Notice out loud, gently. "You sound a bit flat today, is now a good moment to check in?" sits very differently from "are you OK". The first names a specific observable; the second invites the polite "yes I'm fine" that closes the conversation.
- Hold the silence. Most managers, anxious, fill the pause with reassurance or solutions. The good move is to wait long enough for the person to actually answer. Most people know what they need; the conversation usually goes wrong when they are interrupted.
- Name the next step, specifically. "I'm going to drop the Thursday meeting from your diary this week, and I'll check in again Monday." A concrete, manager-owned action with a date. The behaviour most commonly missing from cases that go on to long-term absence is the specific follow-up.
None of these moves are in the Equality Act. All of them are observable. None of them transfer reliably from a slide deck.
What We Do About It
Our manager workshops and immersive simulations are designed for exactly this corridor conversation. Small groups of managers walk into a designed scenario. Professional actors play the team member who says "I'm fine" in a voice that is not fine, the colleague returning from a stress-related absence, the high performer whose work has quietly tailed off. The manager has to run the conversation live, with feedback, more than once. By the third repetition, the noticing-out-loud move is the default rather than the exception.
In Sidestream's own academic behaviour-change work, building on research from UCL, Cambridge and Bocconi, participants who learned a communication skill through immersive role-play scored roughly 20% higher on observed behaviour than those who learned the same content through video or slide-show training. Self-rated confidence did not predict observed performance: a Dunning-Kruger pattern we designed out of subsequent studies by replacing self-reports with behavioural measurement. The implication for the 9.4 days is simple. The lever is not another awareness module. The lever is the conversation rehearsed often enough that, in the live corridor moment, the manager does not freeze.
The 9.4 days is what untrained managers cost. The 73% confidence figure among trained managers is what the same investment buys back.
The absence number is not going to fall on its own. It will fall when the conversations that catch the early signal are conversations your managers have run so often they are boring. Read our piece on the 35% who do not raise it with their manager, or book a call to look at what manager rehearsal would cost in your organisation.
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