Data were obtained from the Study of Adult Cerebral Palsy in Navarra (EPCANA). This cross-sectional study of QoL and clinical and sociodemographic outcomes was conducted at the Spanish Association for the Care of Persons with Cerebral Palsy (Aspace), as part of a comprehensive assessment of QoL, using a disease-specific instrument, the San Martin Scale.

A convenience sample was used, initially composed of 88 institutionalized adults who met the inclusion criteria: adults with any type of cerebral palsy (spastic, dyskinetic, ataxic, and unclassified), classification based on the person's tone and posture,21,22 settled in Navarra, Spain, and who were part of an institution specializing in the care of adults with cerebral palsy, Aspace. The San Martin Scale and the factors and living conditions questionnaire were self-administered in two different years to the same population, between November and December 2021 and in the same period in 2022. Although 88 people were initially considered for the study, only a total of 72 responded to the questionnaire, representing a response rate of 81.81%.

The San Martin QoL Scale23 is based on the multidimensional model of QoL developed by Schalock et al.24 It is the first scale built to assess the QoL of people with significant disabilities and is validated and accepted internationally.23,25 The instrument consists of 95 items, organized around the eight domains of QoL, which include observable aspects and objectives of QoL (see Table S1 in Supplementary material). This scale is adapted to a self-report or proxy report. The respondent is asked to answer the questions with a 4-point Likert-type style: never=1, sometimes=2, often=3 or always=4. Responses from the San Martin Scale are often used to obtain a single QoL value via the Quality of Life Index (QoLI) and this value is reported in clinical studies. The San Martin Scale measures QoL over a range of values from 52 to 132 points.26 A higher score represents a higher QoL on the QoLI. The total score of the San Martin Scale is obtained by measuring QoL in eight dimensions26 (Fig. 1).

Figure 1.

Structure of the San Martin Scale, showing the breakdown into eight domains and ninety-five items. The items are related in each dimension. All dimensions have 12 items, except for the social inclusion domain, which has 11 items. Own elaboration, based on the Scale Manual26 (see Supplementary material).

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When the San Martin Scale is administered to an individual, the responses that the individual has given per question (item) are obtained. By adding the responses for each item, the total direct scores for each dimension are obtained. Having the total direct scores of the dimensions, these are transformed into standard scores, using Table A in Annex A of the San Martin Scale manual26. Once having the standard scores for each dimension in on are obtained, they are summed up to obtain the total standard score. This total standard score is converted to a QoLI using Table B in Appendix A of the San Martin Scale manual23,26. For example, Figure 2 presents the total standard score sum for the eight dimensions of “106”, then when converted to a QoLI equal to “119”, with a percentile of “90” (see Annexes A-B in Supplementary material).

Figure 2.

Example of how to calculate and interpret the San Martin Scale when administered to an individual. Own elaboration, based on the Scale Manual26.

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Additionally, other factors and living conditions with some impact on the QoL of individuals with cerebral palsy11,27,28 were evaluated. A complementary questionnaire was designed of nine items: age, sex, place of residence, degree of dependence, percentage of disability, type of cerebral palsy, cerebral palsy-related disorders, length of time with the institution, and type of service enjoyed in the institution (residence, school, occupational center, day center).

The main characteristics of the sample were presented by means of a descriptive analysis of all the variables used in the study (sociodemographic, clinical and diagnostic, degree of institutionalization). In addition, the results of the global QoL and by dimensions of the San Martin Scale were obtained, showing the mean QoL of the 72 adults with cerebral palsy and the standard mean scores for each dimension and year. The analysis concludes with the translation of these scores into the respective QoLI, following the San Martín Scale manual.26

The estimation of the relationships between the QoLI and the sociodemographic, clinical, diagnostic, and characteristics corresponding to the degree of institutionalization was performed using the ordinary least squares (OLS) and ordered Logit method. In addition, the relationship between all categories of variables with the overall QoL scores of the sample was estimated. The estimation of the OLS models was based on the stepwise forward method, which was complemented by an analysis of the robustness of the models with goodness-of-fit criteria. In order to carry out the estimation using logit models, the QoLI variable has been categorized into three levels by setting as benchmarks for the scores of the San Martin scale values below 110, between 110 to 119, and 120 or above. The starting point was 110, because it is a value close to the mean reference score in the scale validation population (M=100),25,26,29 to consider a poor QoL below this value and a better QoL above this value. The value of 120 was chosen because it represents the 90th percentile of the scale.26

The OLS and Logit models estimate QoLI, a model-dependent variable representing an individual's QoL in 2021 or 2022. SEX is a dummy variable (1 for male, 0 for female), POR represents residence (1 for main city where Aspace is located, 0 for outside), and AGE indicates the respondent's age in years at survey time.

PDD indicates disability percentage (0% to 100%). DOD1, DOD2 (reference), and DOD3 are dummy variables representing moderate, severe, and high dependence, respectively. Each equal 1 if individual i has that dependency level, 0 otherwise. CPRD is a dummy for cerebral palsy-related disorders (1 for cerebral palsy-related, 0 otherwise). CPT1, CPT2, CPT3, and CPT4 (reference) denote cerebral palsy types: spastic, dyskinetic, ataxic, and unclassified, respectively. They equal 1 if individual i has that cerebral palsy type, 0 otherwise.

Binary variables RSD (residences), OCRS (occupational center and residences), SCRS (school and residences), DCRS (day center and residences), DC (day center), and SC (school, reference category) depict an individual's service utilization in the institution. They are 1 when the service is used and 0 otherwise (individuals can use multiple services simultaneously). The continuous variable Inst is a variable that relates the TVA (time that the individual has been in the institution) with age (specifically calculated as the quotient between TVA and AGE), which is interpreted as the degree of institutionalization of individual i as a function of the time the individual has been in the institution corrected for her age.

Data management was carried out using Microsoft Excel, and R statistical software version 4.3.2 was used for statistical analysis.

The EPCANA study protocol and amendments were approved by the Research Ethics Committee of the Public University of Navarra (no. 026/23).

The global mean score obtained for the QoLI indicator of the 72 participants was (mean=110.3; standard deviation [SD]=10.9) over the two years26 (see Figs. S1-S2 and Table S1 in Supplementary material). This indicates that it is a good QoL concerning the mean of the adults with significant disabilities with whom this scale was previously validated (mean=100; SD=15).25,26,29

When analyzing the aggregate data of the eight dimensions that make up the QoLI, it was observed that only one of the dimensions, social inclusion (mean=10.1; SD=3.1) reached the theoretical midpoint of the scale when it was validated (mean=10; SD=3).26,29 Otherwise, all other dimensions were above this mean. The dimension that reached the highest mean score was self-determination (mean=12.92; SD=2.8). These results show that the QoL of the people to whom we administered the San Martin Scale is above the mean obtained by the 1,770 people with significant disabilities who made up the scale's validation sample29 (Fig. 3).

Figure 3.

Mean score by dimension of the San Martin Scale (2021-2022).

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Likewise, to study the possible relationship between the different variables and the dimensions of the San Martin Scale, multivariate models were estimated by year (Tables 2-4). In turn, it was shown that the “degree of institutionalization” was positively related to the dimensions of QoL in the San Martin Scale. It should be noted that the relationships between the different variables included in the models and the QoL of patients generally remain stable, both over the years and across the different estimation methods used in the analysis.

Model 1 emphasized the impact of socio-demographic variables, revealing that residing in the main city showed a strong positive association with QoL in both years, with significant p-values (p <0.1 in 2021 and p <0.05 in 2022). This remains the case for the year 2022 in the estimation using ordered Logit. Furthermore, in 2022, sex emerged as a significant factor, with males in urban settings showing higher QoL scores in the OLS estimation in 2022 (p <0.1) and in the Logit estimation in 2022 (p <0.05). Model 2 extended the analysis to include clinical and diagnostic variables, highlighting a significant negative relationship between high dependency and QoL (p <0.1 in 2021 and p <0.05 in 2022), while residing within the city was positively associated with QoL in 2022 (p <0.1).

Models 3 and 4 investigate QoL in the context of socio-demographic factors and degree of institutionalization, revealing significant associations between duration of institutionalization, city residence, and degree of institutionalization, with p <0.1 in 2021 and p <0.01 in 2022. Finally, model 5, which encompassed all the study variables, identified high dependency as a factor reducing QoL (p <0.1) and higher institutionalization as a factor increasing QoL (p <0.05).

In all models, whether linear or Logit regression, the variable representing the degree of institutionalization (Inst) emerged as significant. As institutionalization increased, so did the QoLI scores. Similarly, the POR variable was significant in most multivariate models, particularly for individuals who resided outside the main city and commuted daily to receive services, resulting in lower QoL scores due to mobility barriers. Another significant variable was the degree of dependency; as dependency increased, QoL decreased significantly.

One of the main limitations of this study is the size of our sample. This represents a low statistical power in our statistical analysis. For this reason, our study is exploratory, so our results and conclusions should be confirmed in future research with larger samples. Our results should be considered in the context of this specific sample and may not be easily generalizable to other conditions. In addition, a possible overrepresentation of adults with grade III dependence and spastic cerebral palsy should be considered.

An important strength of our study is the assessment of self-perceived QoL in adults with cerebral palsy, a topic that has so far been little explored. Furthermore, in our study, we have used a specific instrument, in contrast to the predominant focus on younger populations and generic assessment tools in existing research. These findings are important for future research on QoL among the adult cerebral palsy population to evaluate rehabilitation interventions based on institutional settings.