The quality of life in children with spinal muscular atrophy: a case–control study

Spinal muscular atrophy (SMA) is an inherited autosomal recessive disease [1] characterized by degeneration of alpha motor neurons of the spinal cord, resulting in generalized muscle weakness and atrophy [2, 3]. SMA is the second fatal neuromuscular disease after cystic fibrosis, with an estimated incidence of about one in 6000–10,000 live births and a carrier frequency of 1/40–1/60 [4, 5].

The clinical manifestations of SMA are divided into three major categories in childhood according to the age of onset and motor function achieved [6]. The spectrum of muscle weakness in SMA ranges from extremely compromised neonates to minimally affected adults with late-onset [6, 7]. Generally, the severe form of SMA is type I which is manifested by muscle weakness and hypotonia. Children who suffer from SMA type II are able to sit, but they need aid for standing or walking; and finally, the mild form of SMA is type III who learn to walk unaided [5, 8].

Since these patients will need nursing support due to losing their motor function or respiratory compromise or nutritional problems in advanced stages [2, 9], they would be dependent on others and therefore their quality of life is touched. Since the severity and timing of these complications vary according to the type of disease [1, 10], this factor can also affect the extent of patient dependency on others. In addition, factors such as the socio-economic status of patients and the level of their access to appropriate health care can have a significant effect on their quality of life [11].

Health-related quality of life (HRQoL) is a multidimensional framework that generally evaluates social, psychological, and physical functioning of a patient [12]. Although HRQoL tools are described according to individual perspective of one’s life status along with personal judgment over patient's health and disease and also norms of the community in where they live [13], various studies indicate these tools are reliable in the assessment of standard cares that patients receive [14, 15]. There are controversy results in subscales of the quality of life in various studies and most of them do not report their results according to SMA type and demographic data [16‐20]. In the current research, we aimed to answer the following questions:

First, Does HRQoL of SMA children differ from that of a matched healthy control group? Second, Does HRQoL of children with SMA vary according to SMA type? Third, Does HRQoL of SMA children differ according to demographic and clinical features?

Among 66 children with SMA, there were 12 (35.3%) boys and 22 (64.7%) girls with SMA type II, and there were 19 (59.4%) boys and 13 girls (40.6%) with SMA type III. The mean (SD) age of children with type II SMA was 11.3 (3.5), and it was 15.5 (3.4) in children with type III SMA. Based on SMA type, there was no significant difference between the age of boys and girls.

Table 2 indicates that the health-related quality of life between children with type II and type III SMA is not significant in all 5 subscales, both children's and parent's perspectives.

Table 3 demonstrates that the health-related quality of life in healthy children is significantly higher than in SMA children in all 5 subscales, both children's and parents’ perspective. The highest mean difference was observed in physical and psychological well-being. Moreover, no significant difference was detected between children's and parents’ perspectives in reporting health-related quality of life.

The quality of life in children with SMA was varied according to demographic and clinical features. SMA children whose mothers had less than 12 years of education and also SMA children with history of mood disorders had significant lower score in Physical and psychosocial well-being, and also parent relationships. Low education of fathers also associated with all subscales of the SMA children’s quality of life except physical well-being subscale. Each of demographic and clinical variables is associated with a different subscale of quality of life, details have been shown in Table 1.

In this case–control study, the quality of life was compared between SMA children and a healthy control group, between type II and type III SMA, and also the quality of life was compared according to demographic and clinical features in children with SMA.

The current study indicated that the quality of life in children with SMA varies from that in the matched healthy control group in all subscales. It is important to note that two subscales of quality of life, including physical and psychosocial well-being, were more affected in SMA patients. A systematic review has recently indicated that all subscales are affected by SMA to some degree, however physical well-being is the main domain of life impaired by SMA [23]. Due to the similarity of locomotion impairment on quality of life in neuromuscular disorders, the most common childhood neuromuscular disorder, Duchenne muscular dystrophy (DMD), was considered in the literature review [24]. Most case–control studies have been indicating that the quality of life varies in all subscales [16‐18, 25]; however, Zamani et al. [22] observed the low scores in just two subscales, including physical well-being and peers. Opstal et al. [26] observed the low score only in the physical well-being subscale. The differences across studies may be explained by the small sample size and the type of questionnaire used [18], according to a systematic review conducted by Landfeldt et al. [24], 40% of the studies had been done with a small sample size (less than 35).

We did not find any significant difference between the quality of life in children with SMA type II and type III. Since studies have evaluated QoL by different tools [24] and most of them do not report their results according to SMA type, demographic data, or functional ability [19, 20, 27‐29], it is hard to draw an appropriate conclusion over the observed differences. However, an inverse association has been suggested by some data [23].

This study showed that girls with SMA had a better score in the social environment subscale in compare to the boys. It may be due to different interests and styles of life in different genders in this age group in Iranian children. However, planning for the promotion of this aspect for the both genders to improve their participation in social activities, including supportive consultation, and providing recreational and educational facilities to change the patient's attitudes is recommended [22].

The current study declares that the quality of life in children with SMA varies in comparison with healthy control group in all subscales. However physical well-being and psychosocial aspects are the main domains of life impaired by SMA disease. We did not find any significant difference between the quality of life in children with SMA type II and type III. Furthermore, better social score in girls is seen in comparison with boys with SMA patients that may be due to different interests and styles of life in different genders in this age group in Iranian children. At the time of doing this study none of the patients had access to advanced treatments, for sure the QoL after access to new treatment and the multidisciplinary clinic would differ. So, a new study to evaluate and compare the issue of QoL after access to treatment in these patients is recommended.