We showed that on average 14 years after an ischemic stroke in a young adult almost one out of five long-term survivors (18.8 %) was not able to function independently based on the mRS. In surviving TIA patients this is one out of ten patients (9.8 %). About 1 out of 8 (11.5 %) of the surviving patients with a good functional outcome during the first follow up (on average 10 years after the qualifying event) lost independency in daily life or died during the second follow up (on average 14 years after the event). In contrast, almost one out of six (15.6 %) of the very long time survivors improved to a good functional outcome on the iADL in comparison to the first follow-up moment.
The strength of our study was the long follow-up duration, which is the longest follow-up reported in the field of young stroke, and the ability to detect change in prognosis due to repeated follow-up assessments which enabled us to give more accurate information about the very long-term prognosis after stroke at young age. In addition, our study had a prospective and single center design, which allowed us to collect information systematically and to uniformly verify both the index event as well as the outcome, thereby reducing the risk of information bias, although a single center design could limit the generalizability slightly in comparison to multi-center designs. However, the risk of this is low, therefore we consider it likely that our results can be generalized to most of the young stroke population, especially those who are already months to years past their initial stroke.
However, there are also some limitations. Selection bias may have occurred due to selective loss to follow-up. Both patients lost to follow-up and refusers suffered substantially more often from hypertension at baseline. Therefore non-participants possibly were at a higher risk of incident events and thus an increased risk of a poor functional outcome. Our findings therefore most likely represent an underestimation of the true long-term functional prognosis after stroke in young adults. In addition, possibly not all deficits reported in either of the questionnaires were caused by direct effects of the index stroke, since comorbidity can also lead to the inability to function independently. However, irrespective of the disease underlying the loss of independence, it is remarkable to note the large proportion of still young patients that require help in daily life, on average 14 years after stroke. Finally, during the long inclusion window there have been considerable changes in stroke care, possible resulting in changes in prognosis after stroke at young age as well. We did show a worse prognosis in patients who were admitted with their index event longer ago, however, it cannot be concluded that this is (entirely) due to these changes in care, since these patients also have been at risk to develop recurrent events and comorbidities for a longer period of time.
In previous studies, poor functional outcome in young IS patients ranged from 3 to 7 % after mean follow-up duration between 4 and 12 years [21, 25, 26], better than in our study. This could partly be explained by inclusion of older patients (up to 50 instead of 45 years of age) in our study. Furthermore, in these previous studies functional outcome was measured only by either the mRS or the Glasgow Outcome Scale (GOS), which are commonly used, but are rather global scales for outcome. We intentionally used an additional, complimentary method to determine functional outcome. The iADL (only for survivors) takes into account the ability to perform very specific tasks relevant for living independently, whereas the mRS is a functional outcome measure that is very much dependent on motor performance. These tasks not only rely upon physical health, but also require cognitive function at some level . Consequently the use of these cut-offs of these different scales will result in different groups.
‘Statistics Netherlands’ published data on disabilities in the general Dutch population . Unfortunately the iADL scale is only reported in patients over 55 years of age. However, they do provide information on disability on an OESO-scale, which gives quite a similar impression of disability as the iADL scale. Items on this OESO-scale are walking unaided by another person for 400 m, taking part in a conversation, reading a paper, carrying groceries, picking up an item from the floor. They report that 14.0 % of people between 50 and 55 years (the average age of our patients at follow-up) experience problems on at least one of the items of this scale (in our study 15.2 % of TIA patients and 22.9 % of IS patients experienced problems in iADL). Younger people experience this in ≤7.1 % of the cases. Although this is not a case controlled study, especially IS patients have a much higher (50 %) risk of disability than individuals from the general population.
Finally, we attempted to identify risk factors for long-term poor functional outcome. Interestingly, women had a two to threefold higher risk of a poor outcome than men. This sex-difference in long-term functional outcome after stroke has previously been described in the elderly stroke population [2, 6, 29]. It is assumed that the sex-differences could be (partially) explained by a more advanced age, poorer prestroke functionality, more comorbidities, a tendency to suffer from more severe strokes and less social support in women in comparison to male stroke patients [2, 6, 29]. In our study we observed the increased risk of poor outcome in women despite adjusting for stroke severity, age at initial stroke and the presence of incident events, implying that other underlying mechanisms are involved. There is ongoing research to identify biological mechanisms clarifying the sex-differences in stroke patients, which mainly focuses on the role of sex steroid hormones .
Providing patients and relatives with information is an important aspect of clinical practice. Therefore, it is important to realise that female sex and the initial stroke severity are the strongest baseline determinants of poor long-term functional outcome. In addition, higher age at the time of the index event is associated with an increased risk of poor functional outcome. These parameters are objective, easy to assess and readily available in the acute phase. Patients and their caregivers should be informed about the long-term prognosis to give them the opportunity to make educated choices about career moves and family planning.
In conclusion, the very long-term functional prognosis after young stroke is worse than previously assumed. Up to one out of five young ischemic stroke survivors is not able to live independently almost 14 years after stroke. In addition, very long-term poor functional prognosis was seen in almost one out of ten young TIA survivors. This is important information for patients, their caregivers and for health professionals when counselling their patients on the course of the disease. In addition, the continuous decline in functional outcome long after the initial stroke seen in our population suggests that long-term care and follow-up is needed for young stroke patients. Further research is needed to clarify the etiology and to identify explanations of the observed sex differences of the ongoing decline in young stroke patients and to assess whether additional preventive strategies could decrease the proportion of patients with late deterioration.