From Winter Beds & Unscheduled Care, to Patient Crisis Predictors I Three Years of Learning in Sickle Cell Care.

As we celebrate SCD awareness month, I have been reflecting on our work in actively tracking VOCs for the past 3 years. Like clockwork, and as the seasons change, we tend to see significant peaks in hospitalisations for people living with Sickle Cell Anaemia in the UK and US. The shift in weather, which has long been recognised as a significant contributor to VOCs, partly drives this.

Across the wider SCD cohort, pain scores rise in tandem with higher numbers of reported VOCs during seasonal transitions, particularly into the colder months. Our longitudinal analysis shows mean pain scores climbing well above baseline during the autumn-to-winter shift, with larger clusters of VOCs reported in these periods. This pattern, repeated consistently over multiple years, reinforces what patients and carers already know from experience — that colder weather brings heightened risk.

Indeed, our previously published work exploring the prodromal stage of VOCs through patient workshops designed to capture firsthand experience highlighted cold or shifting weather as one of the three most commonly reported triggers. Patients described how these factors frequently preceded the onset of VOCs by several days, with fatigue and reduced sleep emerging as early warning signs alongside emotional and physical stress. These insights, supported by wearable biometrics showing measurable changes in sleep and heart rate during the prodromal period, reinforce the role of environmental and lifestyle factors in shaping seasonal vulnerability.

Within this overall trend, individual reporting reveals more varied experiences. For some patients, sharp rises in pain and fatigue appear almost predictably each winter, year after year. For others, fluctuations are more sporadic or prolonged, shaped by lifestyle, demographics, and treatment regimens. When examining multiple patients side by side, these differences become even clearer. Daily reporting of pain and quality of life shows how VOC onset is often preceded by directional shifts several days before a crisis. While the wider seasonal pattern is consistent, the exact trajectory is personal, reflecting the unique circumstances of each patient.

So how do you predict this? Well, if we think about predicting A&E demand in the winter, it is relatively straightforward given the pressures of flu, respiratory illness, and cold-related exacerbations. Yet, every year, hospitals still lose control of the front door and their bed base. The same applies to SCD, where predictable surges in VOCs during colder months continue to stretch already pressured systems. Our data not only validates these surges but also highlights important differences across settings.

In the UK, patients consistently report higher symptom severity during VOCs, particularly in pain, mobility, and psychological measures, compared to India, where climate variation may be less extreme but still linked to VOC activity. These cross-regional insights underline the importance of tailoring support, particularly during winter, and provide the foundation for building predictive tools that can help patients and systems anticipate demand rather than react after the fact.

“As I headed into September, I started to feel more pain and fatigue with the weather change, and for the past three years I have consistently been admitted to hospital in the winter. With the Sanius Health predictor and self-management support, I am keen to ensure I can get through the winter without hospitalisation this year.” – Alex

Stories like Alex’s show why prediction matters. By combining daily patient-reported measures with advanced deterioration monitoring, we can align early warning signals from patients with predictive models that flag when a VOC is likely to occur. What we see is striking: self-reported changes in pain, tiredness, and wellbeing consistently map against predictor outputs, often several days before a crisis. This creates an opportunity to act earlier, keep patients well at home, and reduce unnecessary admissions.

Three years of consistent data, across geographies and patient groups, has shown us that VOCs are not random. They follow patterns that can be tracked, anticipated, and managed with the right tools. As we move into another winter, our focus is clear: to continue empowering patients with visibility of their own health, supporting carers with timely insights, and helping health systems stay ahead of predictable surges. By listening to patients, measuring consistently, and learning year on year, we are building a future where staying well through the winter is no longer the exception, but the norm.