Spontaneous intracerebral hemorrhage (ICH) is a devastating form of stroke that could results in focal neurological deficits and high mortality rates, which accounts for 10–20% of all strokes (van Asch et al., 2010). Although ICH traditionally perceived as a disease of older age, the prevalence in younger individuals is increasingly emerging as a public health issue (Krishnamurthi et al., 2014), often leading to permanent disability and imposing a heavy burden on society and economy.

The incidence of ICH in Asian populations was observed approximately double that in Western countries (Jacobs et al., 2002; van Asch et al., 2010), indicating a significant ethnic disparity in the occurrence. Considering the relatively longer life span of young patients, it is critical to clarify the risk factors affecting their functional outcome. However, few studies have investigated the risk factor profile and underlying etiologies for ICH among Chinese young patients (Qureshi et al., 2001, 2009; Keep et al., 2012). Therefore, there is a critical need for studies that targeting young adults to improve our understanding of the impact and develop appropriate prevention and treatment strategies.

In this study, we aimed to investigate the differences in risk factors and clinical characteristics in young and old patients, and to analyze the factors that influence early mortality and functional outcomes between different age groups.

Our results provided the clinical characteristics and prognostic factors of non-traumatic ICH in young patients, and compared the results to those of the elderly. The incidence of ICH is considerably affected by factors such as age, gender, and ethnic disparity (van Asch et al., 2010). Over the past few decades, there has been a global decline in the incidence of ischemic strokes. However, the incidence of hemorrhagic strokes has not followed the same trend (Feigin et al., 2009). Furthermore, non-traumatic ICH in young individuals differs in several key aspects from that in older individuals, and there is a lack of attention and comprehensive guidance for physicians regarding the diagnosis and treatment strategies for ICH in young patients.

Analysis of the 2010 Global Burden of Disease data revealed the incidence of cerebral hemorrhage doubled in younger age groups and was concentrated in low- and middle-income countries (Krishnamurthi et al., 2014). A previous report in 2010 highlighted that the incidence of ICH was 1.9 cases per 100, 000 individuals worldwide among those under 45 years of age, with an escalation to tenfold in the 45–54 age group, and a nearly twentyfold rise in the 55–64 age group (van Asch et al., 2010). Our finding was consistent with this, showing that the highest frequency of ICH in our center occurs in the age groups of 50–59 and 60–69.

Among the participants in our analysis, 68.4% were male, and men appeared to have a higher likelihood of experiencing ICH than women across various age groups. This finding is consistent with a 2015 study in Finland (Koivunen et al., 2015a), where the incidence of non-traumatic ICH was notably higher in men (6.2 cases per 100, 000 individuals; 95% CI 5.0–7.3) than in women (4.0 cases per 100, 000 individuals; 95% CI 3.4–4.7). The male predominance in stroke events can potentially be attributed to the higher prevalence but lower control rate of risk factors (Nzwalo et al., 2018; On et al., 2022).

It has been reported that the etiology of ICH in young patients more often involves structural abnormalities and uncommon underlying factors (Koivunen et al., 2015a). The majority of new evidence in the field of ICH in young individuals comes from genetic research, revealing numerous previously unknown genetic loci associated with brain hemorrhage. These studies have the capacity to offer new insights into the mechanisms of ICH in young patients. In this study, 91.7% cases were caused by primary ICH. We noted that younger population was more frequently associated with secondary ICH, such as arteriovenous malformations, arterial aneurysms, or moyamoya vasculopathy, markedly differing from older patients.

We also showed that the risk factors differ between age groups. Nevertheless, hypertension emerged as the predominant risk factor within both age categories. Younger patients with ICH manifested less frequent diabetes rates but higher body mass index (BMI) compared to older individuals. Prior investigations have established a correlation between elevated BMI, increased high-density lipoprotein (HDL) cholesterol, and the incidence of ICH (Chen et al., 2017; Yang et al., 2020). Therefore, it is necessary to control the aforementioned modifiable risk factors, such as hypertension, diabetes and BMI, to reduce the hemorrhagic stroke occurrence.

Furthermore, our results indicated the white blood cell count was independently associated with poor outcomes in young patients. On the progress of intracerebral hemorrhage, an inflammatory response occurs as a consequence of cerebral vascular bleeding and acute stress reaction, which is accompanied by an elevation in inflammatory markers such as WBC (Di Napoli et al., 2011). In addition, severely ICH patients may experience impaired consciousness and swallowing dysfunction, increasing the risk of developing aspiration pneumonia (Wang et al., 2021). These acute infections can also lead to an elevation in WBC count. Prior research suggested a significant association between elevated inflammatory markers and hematoma growth (Di Napoli et al., 2014; Morotti et al., 2016), as well as a higher incidence of unfavorable clinical outcomes (He et al., 2023).

Prior studies reported that increasing age, baseline NIHSS, baseline GCS, hematoma volume, the presence of hydrocephalus, herniation, renal or heart disease, and multiple hemorrhages were associated with the case-fatality in ICH patients (Hemphill et al., 2001; van Asch et al., 2010; Koivunen et al., 2014, 2015b; Rutten-Jacobs et al., 2014; Yang et al., 2020). Our study were also consistent with these studies, we found the factor associated with patients' 3-month functional independence were the previous medical history of nephropathy and stroke events, age > 50 years, higher NIHSS scores, larger hematoma volumes and the presence of hydrocephalus.

The severity of neurological impairment upon admission demonstrated no significant age-related differences. Similarly, there was no statistical difference between the two groups in 1-month mortality rate (17.5 and 18.8% for young and elderly patients, respectively). However, a marked improvement in outcomes at 90 days was significantly evident among younger ICH patients, suggesting that the rehabilitation rate is more favorable among younger survivors. As evidenced by our study, potential explanations for the observed improved outcomes in younger patients could be attributed to their enhanced neuroplasticity and a lower likelihood of experiencing complications (Koivunen et al., 2014; Yang et al., 2020). Furthermore, the prevalence of vascular risk factors increased with age, younger patients typically exhibit fewer individual risk factors, which contribute to their more favorable outcomes. Emerging evidence supported an aggressive therapeutic approach for spontaneous ICH in young patients, including aggressive blood pressure reduction (Anderson et al., 2013; Qureshi et al., 2016), selective surgical hematoma evacuation (Lai et al., 2005; Koivunen et al., 2014), and intensive rehabilitation.

We recognized several limitations in this study. First, this is a single-center study, our results need to be confirmed by multi-center study. Second, there are additional important young-adult-specific risk factors, including drug abuse, pregnancy, and the postpartum period, however, our current research was lacking in data pertaining to these factors. Third, different levels of nursing care quality may also contribute to the prognosis of ICH patients. It's important to acknowledge that there are variations in the nursing care quality among the patients in this study.

In summary, our study demonstrates that spontaneous ICH in young adults had higher white blood cell and BMI compared to the elderly, and differs in etiological distribution. The young patients also had similar short-term mortality but more favorable functional outcomes. Furthermore, NIHSS score and larger hematoma volumes were associated with poor outcome in all age groups.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving humans were approved by the Ethics Committee of the First Affiliated Hospital of Chongqing Medical University. The studies were conducted in accordance with the local legislation and institutional requirements. The human samples used in this study were acquired from a by- product of routine care or industry. Written informed consent was obtained from all participants or their legal surrogates.

CC: Methodology, Writing—original draft. YX: Methodology, Resources, Writing—original draft. MP: Resources, Writing—review & editing. LD: Resources, Writing—review & editing. ZL: Resources, Writing—review & editing. TY: Resources, Writing—review & editing. HY: Resources, Writing—review & editing. ZZ: Resources, Writing—review & editing. XLv: Resources, Writing—review & editing. XLi: Resources, Writing—review & editing. JC: Resources, Writing—review & editing. QL: Conceptualization, Data curation, Funding acquisition, Supervision, Writing—review & editing.