Our study examined the relationship of the use of antipsychotics during the first 4 weeks of hospitalization with HG and SMI at discharge in older patients with sarcopenia undergoing convalescent rehabilitation after stroke. The most important finding of this study was that the use of antipsychotics at the first 4 weeks after admission was negatively associated with HG at discharge. The second most important finding was that the use of antipsychotics during the first four weeks of hospitalization was not statistically significantly associated with SMI at discharge.
As mentioned, the association between medication use and muscle strength has already been reported [12–16]. However, our study differs from many other studies in that we focused on antipsychotics. Of note, our study is the first to demonstrate that the use of antipsychotics is negatively associated with strength such as HG. Furthermore, the associations shown in our study between age, antipsychotic use, LOS, ADL, rehabilitation, protein intake, and CCI indicate how interwoven older specific clinical conditions are. The mainstay of treatment for sarcopenia is muscle mass and strength increase through exercise and nutritional interventions. However, based on our results, it is necessary to consider not only exercise and nutritional interventions, but also the effects of medications, especially antipsychotics.
The use of antipsychotics at the first 4 weeks after admission was not statistically significantly associated with SMI at discharge. However, in some cases, muscle mass alone is not sufficient for understanding the condition of muscle function. In other words, muscle mass does not necessarily correlate with muscle strength, and high risk of functional impairment is associated with weak muscle strength, even if the muscle mass is high. Morphological and functional factors are involved in the exertion of muscle strength. The morphological aspect is the cross-sectional area of muscle fibers and the muscle fiber composition. Muscle strength exertion is proportional to the cross-sectional area of muscle fibers. The central nervous system plays an important role in the function aspect. In other words, when neural activity in the brain is reduced and insufficient information is obtained from the central nervous system, it becomes difficult to exert muscle strength properly. Antipsychotics have an inhibitory effect on the central nervous system by blocking dopamine receptors. Because they suppress the action of dopamine, they also affect motor function. When changes occur in the central nervous system, muscle strength becomes weaker, even if muscle mass is maintained, and the quality of functional muscles is diminished. As such, it is conceivable that interventions to assess muscle strength in addition to muscle mass will lead to improvements in functional prognosis, quality of life, and prevention of adverse events.
The treatment of sarcopenia in rehabilitation settings, including rehabilitation nutrition , and rehabilitation pharmacotherapy [5, 6, 30], should be comprehensive. Sarcopenia can be caused by a variety of factors, including aging, low activity level, and poor nutritional status . However, our results suggest that the use of antipsychotics can also be a cause. Overall, a multifaceted approach from the perspectives of rehabilitation nutrition  and rehabilitation pharmacotherapy [5, 6] is essential for the prevention or treatment of sarcopenia. The usefulness of rehabilitation nutrition  has been established for patients with sarcopenia undergoing rehabilitation. However, evidence regarding rehabilitation pharmacotherapy is insufficient. Our results may provide an opportunity to review the administration of antipsychotics in patients with sarcopenia. It is conceivable that multidisciplinary implementation of nutritional therapy and exercise therapy together with the results of this study will advance the treatment of sarcopenia.
This study has several limitations. First, this was a retrospective cohort study conducted at a single hospital in Japan, which limits its generalizability. However, our results may be useful in an aging population, such as Japan, or in populations with similar prescribing trends. Second, the effects of medications other than antipsychotics were not considered. Finally, electronic medical charts-recorded information was used to capture data; it could not be verified whether subjects used the dispensed medicine. Therefore, future validation in a multicenter, prospective cohort study that takes these limitations into account is desirable.
In conclusion, the use of antipsychotics 4 weeks after admission in older patients with sarcopenia undergoing convalescent rehabilitation after stroke was negatively associated with HG at discharge, but it was not significantly associated with SMI. The use of antipsychotics should be avoided as much as possible in older patients with sarcopenia undergoing convalescent rehabilitation after stroke.