Introduction
The phenomenon of aging is the result of the natural course of time, which causes fundamental changes in different body systems in such a way that the stagnation of mental activities in this period is associated with the decline in the performance of all body systems, including cardiovascular, vascular, respiratory, glandular, safety, and other organs. On the other hand, morphological and biochemical changes in different parts of the brain, such as the parietal and frontal cortex, decrease cognitive performance. Cognitive disorders are one of the common problems in aging, which in turn exposes them to risks, including significant changes in memory, intelligence, perception, metacognition, problem-solving, and other cognitive abilities so that they will no longer be able to make delicate plans and make appropriate decisions in their lives, which will ultimately cause a decline in their quality of life (QoL) with a negative effect on their daily activities. Therefore, this research was conducted to determine the effectiveness of cognitive rehabilitation in improving the cognitive abilities of the elderly.
Methods
The current research was a quasi-experimental type of research with a pre-test and post-test design with a control group. The statistical population included elderly people living in the Eram nursing home in Kermanshah City, Iran, and 24 people who were eligible to enter the study were selected. In addition to stating the purpose and importance of the research, the sample subjects were reassured about the observance of ethical points and they signed the informed consent form to participate in the research. Then the samples were randomly divided into two groups of 12 people and by random method, one of the groups was selected as the experimental group and the other as the control group. The experimental group underwent 20 sessions of 35 minutes, and twice a week under the intervention of Captain Log’s cognitive rehabilitation program, and during this period, the control group did not receive any intervention. A week after the last intervention session, a post-test was performed for both groups. A cognitive rescue skills questionnaire was used to collect data, and for the intervention program, according to cognitive skills variables, 5 programs were selected and implemented from Captain Log rehabilitation software programs. In this way, the method of performing each of these tasks was carefully studied by the therapist and explained to the elderly in simple and understandable language. The program of each session was different and more difficult than the previous session, which motivated the subjects to continue the treatment. In this research, two stages were considered for each session, if the subject passed the stages successfully, he would enter the higher stages in the next sessions. A week after the last intervention session, a post-test was performed for both groups. The data obtained from the questionnaire in the pre-test and post-test stages were entered into SPSS software, version 24. Descriptive statistics and inferential statistics, including univariate and multivariate analysis of covariance were used to analyze the data.
Results
In the data analysis, descriptive indices of the cognitive skill variable and its components were done separately for the groups in two situations of pre-test and post-test; the results showed that the average of the experimental group improved from pre-test to post-test. Therefore, as can be seen, the difference between the two groups in the post-test phase was in favor of the experimental group. Covariance analysis was used to analyze the data. For this purpose, the assumptions of the analysis of the covariance test were first examined. Shapiro-Wilk test was used to determine the distribution of the population (data normality), which was 0.25 (P=0.09) and 0.17 (P=0.07) for the variable of cognitive skills in the pre-test and post-test of the experimental group, respectively, and in the pre-test and post-test of the control group, it was 0.17 (P=0.61) and 0.19 (P=0.25), respectively. In the conducted test, the significance level was considered P>0.01, which indicates the normal distribution of the population. Leven’s test of homogeneity of variances was used to check the homogeneity of variance of two groups in the post-test stage. Levene’s test calculated for the variable of cognitive skills and its components were not statistically significant (P<0.05). Therefore, the assumption of homogeneity of variances for the variable of cognitive skills and its components was confirmed. Another crucial assumption of covariance analysis, i.e., the homogeneity of regression coefficients, was performed by examining the interaction effect of the independent variable and the pre-test of each dependent variable on the post-test for variables of cognitive skills (P =0.07 and <0.05, F=0.11) that the results indicated compliance with this assumption. According to the assumptions of covariance analysis, the use of this test is allowed; therefore, univariate and multivariate covariance analyses were used to test the research hypotheses. The results of data analysis in univariate covariance showed that the F statistic of the cognitive skill variable in the post-test is 340.46, which is significant at the 0.001 level, and this shows a significant difference between the two groups in the cognitive skill variable. According to these findings, it can be said that computer cognitive rehabilitation training increases cognitive skills. Considering that the variable of cognitive skills has a subscale, multivariate covariance analysis was used to investigate the effectiveness of computerized cognitive rehabilitation on the components of cognitive skills. The results showed that the F statistic for dependent components, including memory (F=193.57, P<0.001), selective attention (F=375.43, P<0.001), decision-making (F=39.20, P<0.001), planning (F=120.003, P<0.001), sustained attention (F=312.07, P<0.001), flexibility (F=91.44, P<0.001), and social cognition (F=4.48, P<0.05) are significant at the level of 0.05 and 0.01. This shows a significant difference between the two groups in the variable of cognitive skills. Therefore, it can be concluded that the cognitive rehabilitation program has improved the cognitive skills of the elderly.
Discussion
The results of this study showed the effectiveness of the rehabilitation method in increasing cognitive skills in the elderly. The exercises in computer rehabilitation programs increase the performance and mental activities involved in cognitive rehabilitation and as a result, improve cognitive skills. Cognitive defects cause the inability of the elderly to perform daily life activities, as well as their feeling of inadequacy and reduced self-confidence, therefore, cognitive rehabilitation as an independent treatment method with the prevention of cognitive deficits and its treatment can prevent or reduce such complications and ultimately improve the QoL of these people in personal and social dimensions by improving their performance level and ultimately increasing their self-confidence. Therefore, psychologists in nursing homes or psychological service centers and clinics can use cognitive rehabilitation methods along with other treatment and rehabilitation methods to improve the cognitive skills of the elderly.

Ethical Considerations
Compliance with ethical guidelines
The present research was carried out after obtaining permission from the Welfare Department of Kermanshah Province and making the necessary arrangements with the officials of Eram nursing home, following ethical points and obtaining informed consent from the elderly. It was explained to the elderly about the confidentiality of the information and the permission to withdraw from the research. The research had no code of ethics.

Funding
The present article was carried out in the Faculty of Social Sciences, Razi University, Kermanshah Province without financial support and is not derived from a thesis or dissertation.

Authors' contributions
All authors equally contributed to preparing this article.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
Hereby, the researcher appreciates the officials of Eram nursing home in Kermanshah Province.

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