Insights from a 10-Year Australasian Idiopathic Hypersomnia Patient Data Registry Study
- Michelle Chadwick
- Sep 3
- 7 min read
Updated: Sep 3
Current knowledge of idiopathic hypersomnia (IH) symptomatology has been almost exclusively limited to data from patients presenting to specialised sleep centers. However, such data may not accurately represent the broader patient population. Patient data registries are an efficient and representative way to collect information, including demographic information, symptoms, and medication use. These registries have generally been used in more common medical conditions such as dementia and more frequently found sleep conditions such as obstructive sleep apnea. However, data registries may be especially important in the study of rare conditions, such as IH, where gathering consistent clinical data is more challenging.
A U.S.-based IH patient registry study involving 663 respondents with hypersomnolence has described the clinical features of IH, medication use, and differences in symptomatology between patients. This research has provided important insights into the clinical profile and lived experience of people with IH. However, to date, there has not been an IH patient registry study in Australia and New Zealand. Furthermore, no studies have reported patient-driven feedback in IH - an important resource for understanding lived experience and guiding clinicians toward improved care.
Using data collected via the Hypersomnolence Australia Idiopathic Hypersomnia Patient Registry and Hypersomnolence Australia’s “Living with Narcolepsy” survey, our objectives were:
To evaluate the demographics, symptom profiles, concomitant medication use, and medical histories of a large cohort of people with physician-diagnosed IH in Australia and New Zealand.
To report patient-driven feedback to better understand how IH is treated in Australia and New Zealand and identify opportunities for improvement.
To compare reported clinical features in this IH cohort with those of people diagnosed with narcolepsy (type 1 or type 2).
This study analysed data from 686 participants in Australia and New Zealand - 554 with idiopathic hypersomnia (IH) and 132 with narcolepsy (NT1: 54, NT2: 78).
“Unrefreshing sleep” (“wake up from sleep, including naps, not refreshed”) was the most commonly reported symptom, followed by “sleep drunkenness” (“extreme difficulty waking up, multiple returns to sleep”). Most participants reported daytime naps, with long naps (>1 hour) being more common than short naps (<1 hour). 55.6% of people with IH said they experienced automatic behaviour (doing something without thinking and later not remembering doing it - or even that it happened at all). Excessive sleep was reported in 420 (75.8%) of participants. Note: Excessive daytime sleepiness was not assessed because this symptom is necessary for a formal diagnosis of IH and will be experienced by everyone with IH.
When compared with participants from the “Living with Narcolepsy” survey, significant differences were found in nearly all core hypersomnolence symptoms. A higher percentage of participants with IH reported unrefreshing sleep compared with those with NT1 and more sleep drunkenness than those with either NT1 or NT2. NT1 participants more frequently reported regular hallucinations and sleep paralysis than NT2 participants, while participants with NT2 reported regular hallucinations significantly more often than those with IH.
The majority of participants with IH reported never having been diagnosed with any other sleep disorders.
SUMMARY:
Largest IH registry study in Australia & New Zealand (n (total) = 686; IH: 554, NT1: 54, NT2: 78) 🕒 Diagnosis Delay
10.6 years average delay from symptom onset to diagnosis
Mean age of symptom onset: 21.2 years - 70% had symptom onset at 22 years or younger
Mean diagnosis age: 31.6 years
👥 Who’s Affected
80% female (refer to 'Discussion' below)
All Australian states & NZ represented
😴 Core IH Symptoms (without medication for hypersomnia)
Unrefreshing sleep – 95%
Sleep drunkenness – 88%
Long daytime naps (>1 hr) – 71%
Automatic behavior – 56%
Excessive daytime sleepiness was not assessed because it is required for a formal IH diagnosis and is therefore experienced by everyone with IH.
🧠 Non-Core Symptoms
Cognitive dysfunction / Mental fatigue – 80%
Physical fatigue – 74%
Other: low libido (39%), digestive issues (33%), orthostatic hypotension (33%), Raynaud’s-type phenomena (31%)
Orthostatic hypotension = lightheadedness, dizziness, and fainting
Raynaud’s-type phenomena = cold hands and feet/difficulty with temperature regulation
⚕️ Comorbidities
Anxiety – 50%
Depression – 46%
💊 Treatments
Modafinil – 46%
Dexamphetamine – 44%
Some people use a combination of these medications
11% take no medication
💬 Patient Feedback
People want more information from doctors about:
Medication effectiveness (72%)
Long-term effects (70%)
Side effects & interactions (~50%)
Lifestyle strategies (68%)
🔍 Key Takeaways
Patients want more comprehensive pharmaceutical and non-pharmaceutical guidance from clinicians; further research is needed to strengthen evidence-based lifestyle recommendations.
Actigraphy + sleep logs could aid the diagnostic exclusion process and help identify IH cases missed by MSLT.
These findings point to a need for enhanced clinician education on IH diagnosis, management, and patient communication to improve care quality and reduce delays in diagnosis.
Large patient registries are crucial for rare disorder research & care improvement.
DISCUSSION:
This is the first registry study of patients with IH in Australia and New Zealand. It demonstrates the value of patient registries to better characterise symptomatology and comorbidities in physician-diagnosed participants with IH. The results highlight IH symptoms often begin in teenage years and early adulthood, with a mean delay in diagnosis of 10 years.
Half of participants reported anxiety or depression, conditions that may have a complex, potentially bidirectional relationship with IH. These mood disorders may also contribute to delayed diagnosis.
Insight into the lived experience of participants with IH highlighted a need for more information about medication prescribed for IH from treating physicians.
The mean age of symptom onset (21.2 years) and the higher proportion of female participants align with previous studies. The mean age at diagnosis (31.6 years) was also consistent with previous research. This diagnosis delay may be partly due to IH being a diagnosis of exclusion, requiring polysomnography to exclude other causes of hypersomnia including narcolepsy and sleep apnoea, as well as the impact of comorbid mood disorders. Our results support the understanding of additional symptomatic “clues” for IH such as long sleep times and “sleep drunkenness,” which are reported significantly more in participants with IH than in those with narcolepsy. Furthermore, diagnosis could be hindered by diagnostic challenges such as the poor test–retest reliability of the MSLT in hypersomnolence disorders.
Core symptoms reported by IH participants included unrefreshing sleep, excessive sleep, long daytime naps, sleep drunkenness, and automatic behaviour. Research suggests that people with IH often have high sleep efficiency and less sleep fragmentation than healthy controls. Although the mechanisms contributing to unrefreshed sleep are not known, research suggests they do not appear to be caused by poor quality sleep. These symptoms - particularly unrefreshing sleep, excessive sleep, long naps, and sleep drunkenness - are consistent with current IH diagnostic criteria. Mental fatigue and cognitive dysfunction were also frequently reported, though it remains unclear whether these are specific to IH or simply reflect excessive sleepiness in general.
Participants with IH also reported symptoms such as physical fatigue, impotence or low sex drive, orthostatic hypotension, digestive problems, and Raynaud’s-type phenomena. While these have been observed in other studies, no clear causal link with IH has been established. These results demonstrate the heterogeneity in symptoms in IH, adding to the difficulty in making a timely diagnosis. In addition, approximately half of all participants with IH reported having anxiety and/or depression. The relationship between these conditions and IH is not currently known. However, they may also contribute to the delay is diagnosis from symptom onset reported.
Although IH diagnostic criteria focus on MSLT results, our findings support the use of actigraphy (supported by sleep logs) to capture data from patients whose IH primarily manifests as long sleep times and also to assist the diagnostic exclusion process.
Studies directly comparing medication efficacy in IH are lacking. Consistent with the American Academy of Sleep Medicine’s practice parameters, modafinil was the most frequently reported treatment in this cohort, followed closely by dexamphetamine. The Australian Pharmaceutical Benefits Scheme does not subsidize treatment of IH but does subsidize treatment of narcolepsy with dexamphetamine, modafinil, or armodafinil. In Australia, these medications are not subsidised for IH under the Pharmaceutical Benefits Scheme (PBS) but are subsidised for narcolepsy. Because NT2 and IH share some overlapping features, it is not uncommon for people with IH to have accessed these medications via a ‘narcolepsy pathway’ (their diagnosis is recorded as narcolepsy only for the purpose of accessing PBS listed medication).
Patient feedback is a critical tool for understanding the lived experience of rare conditions like IH. In this study, only 12.9% of participants were satisfied with the information provided by their physician, while 11.4% reported receiving no advice at all. Respondents expressed a strong desire for more comprehensive pharmacological and non-pharmacological guidance, highlighting an opportunity for clinicians to focus more on education during consultations.
Other large hypersomnia studies have demonstrated IH to be more commonly diagnosed in females than in males. In our study, 80% of respondents were female. This could potentially be influenced by higher female participation in online surveys and recruitment via support groups.
In summary, this study is the first to provide important and novel insights into the challenges and clinical characteristics of IH in Australia and New Zealand and can help guide researchers and clinicians to optimize patients’ care in this rare population. The challenges include the heterogenous nature of symptoms, which can confound and delay diagnosis.
The study also provides direct feedback to clinicians that can assist future management of these patients. Patients want more comprehensive pharmaceutical and nonpharmaceutical advice from their clinicians, and more research is needed to guide the latter. This study highlights the importance of patient registries to provide education and feedback to both patients and clinicians. Anderson J, Yee BJ, Grunstein R, et al. Insights from a 10-year Australasian idiopathic hypersomnia patient data registry study. J Clin Sleep Med. 2024;20(12):1955–1964.
By joining our Hypersomnolence Australia Idiopathic Hypersomnia Patient Registry, you’re helping to build a stronger foundation for research, education, and advocacy. Registries give researchers and clinicians a clearer picture of what people with IH truly experience, beyond what is seen in clinical settings. Every person who contributes helps us better understand the challenges of living with these rare conditions, identify gaps in care, and push for improved treatments and support. Your participation matters. If you are living with IH please consider joining today and adding your voice to this important work. Together, we can drive change.
👉 Join the Patient Registry
We are also in the process of expanding our registry to include all Central Disorders of Hypersomnolence, such as narcolepsy and Kleine–Levin syndrome (KLS). This expansion will make the registry even more powerful, allowing us to capture the similarities and differences across conditions, improve diagnostic pathways, and advocate more effectively for everyone affected.
