Individuals with Down syndrome (DS) are considered one of the vulnerable groups to COVID-19 infection. The frequency of COVID-19 in the participants of this study was 3.3%. This was less than the percentage reported by Hüls et al. [12] (83% half of them were hospitalized). Hospitalization risk could be linked to cardiovascular diseases [13]. In this study, the low percentage could be attributed to the young age of the participants and overprotection of their parents. It should be considered that the participants were not recruited from general population, yet from those who were visiting the outpatient clinic for special needs children. This would not allow generalization of the COVID-19 frequency output in DS population and this could be considered a limitation of this study. DS population has high risk for infectious diseases due to genetic susceptibility in some genes related to immunity such as IFNAR1/2 and HSA21 genes and the gene controlling TMPRSS2 receptor. Other factors are involved such as obesity, preexisting comorbidities, hypotonia, and ID which could hinder their healthy habits or social distancing [4, 14, 15]. Therefore, when it comes to DS population, extra precautions should be adopted from families and health care systems to avoid infection and they should have the priority to get COVID-19 vaccine [16].
The lockdown has negatively impacted the health of the participants. Many subjects showed signs of sleep disturbance and a decline in their abilities as rated by their parents. This is consistent with other studies who investigated the lockdown influence on populations other than children with DS. Chang et al. [17] and Mohr et al. [18] reported that containments led to reduced physical activities and excess food consumption, weight gain, and behavioral disorders. The participants in this study manifested variable comorbidities, microcephaly, growth retardation, or obesity which were detected by anthropometric measures. These factors could have shared in exaggerating the unfavorable effect of the lockdown on the participants. Anthropometric measures are one of the main methods used to assess the nutritional condition and the physical growth of children which reflect their health status. Even in absence of microcephaly (standard deviation of head circumference less than − 2.5), low brain volume and reduced connectivity between different brain areas could hinder the development of DS children’s abilities which underscores the necessity of rehabilitation sessions [19, 20].
Cognitive impairment was detected by objective assessment in many participants. This delay which was detected even in the group who got the therapy could be attributed to impaired neurogenesis, and alterations of various neurotransmitters and receptor systems such as serotonin, dopamine, and gamma-aminobutyric acid which was previously reported in such children [21]. Cognitive abilities are not similarly delayed in many individuals with DS. Auditory short-term memory and phonological processing are areas of weakness while visuo-spatial processing, social abilities, and shared attention are generally viewed as relative strengths [22]. Pinter et al. [23] detected a disproportionately small cerebellar volume and a relatively large subcortical gray matter volume in comparison to the overall reduction of brain volume. These characteristics could explain why, despite receiving virtual training, the participants' abilities deteriorated. Because of their reliance on social connection, virtual training may have played a limited role in the present study. Other factors include lack of access to the required materials needed for the continuous training, as well as less time available for the child considering that other children in the household are home-schooling during the pandemic.
The language performance of the participants was the most delayed one. This could be related to expressive language deficits which were reported to surpass the receptive ones. The phonological processing (especially that involving phonological loop) is aberrant which could negatively impact expressive language development, especially morphosyntax. A small hippocampal volume, which is important for memory and other cognitive activities, and a small frontal lobe volume, where the expressive language area is located, could potentially have a role [23, 24]. Childhood apraxia of speech, prosodic dysregulation, disfluencies, and malocclusions have also been described in children with DS, all of which may contribute to reduced speech intelligibility, aggravate their communication difficulty, and result in low language evaluation scale scores [25].
Hypotonia, which can lead to muscle weakness and ligament laxity, could be the reason for the delay in motor abilities despite motor rehabilitation sessions. These motor deficiencies could be linked to slow cerebellar growth and structural changes, as well as craniocervical instability, which is observed in roughly 60% of such children [26]. Furthermore, abnormal collagen structure, which is crucial for muscle integrity, was detected in these people and was linked to aberrant COL6A3 gene signaling [5]. Furthermore, the shape of the pelvic spinal area and hips in people with DS differs, which could disrupt their gait [17]. All these factors could have limited the progress despite having virtual physical therapy rehabilitation sessions.
The factors that could be related to having programs and online sessions at home were investigated. Such factors should be taken into consideration by the health care professionals in order to tackle and overcome the factors that could limit the commitment of the parent to implement home-based training for their children in the future and to improve the efficiency of the virtual online sessions. This is attributed to the fact that this pandemic is spreading in waves which could lead to more lockdowns in the future. Family members play a fundamental role in the intervention programs and need to get support, orientations, and awareness from the health providers to ensure the continuity of treatment and rehabilitation at home [27]. Comparison between group I and group II regarding these possible factors was performed. Caregivers with a low education level may have more time to perform home training considering the possibility of being jobless. Being a male and having severe delay in cognitive abilities as judged by the parents may be motivating factors for the family to continue training at home. On the other hand, sleep disturbances manifested by children could have hindered the family from being committed to persistent training during the lockdown. Kumaravel et al. [28] reported other hazards of COVID-19 pandemic containment such as irritation, and post-traumatic stress. They suggested that these hazards can be reduced by internet-based socializing and working. Parent support, community support, information technological support, and loosening quarantine restrictions are suggestions for solutions for the negative impact of the pandemic on families with special needs children [29]. This support should include mental health support together with financial support required for improving the health care facilities and provide proper parental knowledge about the syndrome and enlightenment of how to be involved in the virtual training programs with minimal effort and how to make the home-based intervention funny instead of a burden on the family and the child.