INTRODUCTION
Functional capacity is a complex concept that includes basic activities of daily living (BADL), instrumental activities of daily living (IADL),
1) and advanced activities.
2) Since inadequacies in BADL affect daily activities, work performance, and leisure activities, BADL is one of the most important indicators of success to define the skill level, demonstrate the effectiveness of rehabilitation, and determine a person’s ability to perform activities of daily living.
3,4) The BADL may decline due to age, a specific disease, or a variety of factors such as decreased muscle strength, muscle atrophy, degenerative changes in joints, impaired neuromuscular coordination, loss of vision, and postural changes.
5)
BADL represent the activities necessary for self-care (e.g., bathing, dressing, feeding, etc.) while IADL represent the activities that allow independence in social life.
6,7) In addition to some BADL, IADL also include outside activities such as shopping. Inadequacies in fulfilling IADL cause disability by decreasing the functional capacity of older adults. In 1969, Lawton and Brody
8) developed the Lawton Instrumental Activities of Daily Living Scale (Lawton-IADL) to measure disability levels and assess parameters in community-dwelling older adults. This scale comprises eight items, including the ability to use a telephone, shopping, food preparation, housekeeping, laundry, use of public transportation, managing self-medication, and handling finances. Responses to each of the eight items on the scale are scored as 0 (cannot perform or can partially perform) or 1 (can perform). The total score ranges from 0 (low-functioning, dependent) to 8 (high-functioning, independent). There are Spanish,
2) Hong Kong Chinese,
9) Korean,
10) and Persian
11) versions of the scale.
The Lawton-IADL is the most widely used scale for IADL assessment in older adults. The present study aimed to adapt the Lawton-IADL developed by Lawton and Brody
8) to Turkish and investigate the validity and reliability of the scale in older adults.
DISCUSSION
Declining functional levels in older adults may be directly or indirectly related to their quality of life, major health problems, and mortality.
26,27) Assessment of the independence level of functions helps healthcare personnel to provide appropriate treatment, care, and counseling services by identifying the needs of older individuals and taking necessary measures.
28) This study adapted the Lawton-IADL, which is used to determine the IADL level in older adults, and analyzed its validity and reliability.
Our study group comprised adults more than 65 years of age with no acute health problems. The sociodemographic distribution of the patients showed that most were living alone and had one or more chronic diseases. These results were consistent with the population profiles in the current literature.
29) Similarly, most of the patients were not using any assistive devices (n=63, 78.7%) and their final state assessment scale scores (FIS, 110.0±24.5; BI, 89.9±20.0; Katz Index, 26.0±5.1; Lawton-IADL, 6.1±2.1) indicated high functional levels.
Participants in our study had relatively high cognitive level (HMT, 8.6±0.7). A decline in cognitive function can lead to deficiencies in decision-making ability
30) and subsequent ethical problems in both the clarity of the scale items and in obtaining informed consent. Laudisio et al.
4) observed normal and higher cognitive function adequacy in individuals with HMT scores above 7, while Chen et al.
31) reported that cognitive disorders negatively affected IADL performance. For these reasons, the present study used HMT scores of ≥8 one as an inclusion criterion. Therefore, during data collection, no difficult to understand part was reported from the volunteers for scale questions. Hence, authors believe that the study population is adequete to draw study conclusions of validities.
The Lawton-IADL results showed a higher inadequacy of the ability to use a telephone than other subheadings of Lawton IADL. Vergara et al.
2) also reported a higher inadequacy of this ability compared to the other subheadings of the Lawton-IADL. One possible explanation for these results may be the late entry of phone use in the lives of individuals over 65 years of age and the late increase in its prevalence. No widespread inadequacy was observed for other subheadings of the scale.
The Cronbach’s alpha value, which indicates the internal consistency of the scale, was excellent (0.843). The Cronbach’s alpha scores for the Chinese (Hong Kong), Korean, and Spanish and Persian versions were 0.86, 0.90, and 0.94, respectively.
2,9-11)
Our study evaluated the Lawton-IADL’s temporal reliability by the test-retest method, with an ICC value of 0.915, compared to 0.96 for the original version of the scale.
8) The test-retest method was used to determine the reliability of the Chinese, Korean, and Persian versions of the scale, with values of 0.90, 0.90, and 0.99, respectively.
9-11) In the Spanish version of the study, the Comparative Fit Index was 0.99, with values >0.90 considered satisfactory.
2) These results are similar to those of our study; the high ICC values in the Turkish version, show that the translation did not change the characteristics of the scores to a large extent.
Assessment of the test-retest correlation coefficients for the subheadings revealed the lowest value for the ability to use the telephone (0.74); however, even this value was above the threshold value for correlation.
The original version of the study investigated the correlations of the scale with the Physical Classification, Mental Status Questionnaire, Behavior and Adjustment rating scales, and Physical Self-Maintenance Scale (PSMS) scores. The Lawton-IADL showed a good correlation with the PSMS and moderate correlations with the other scales, thus supporting the validity of Lawton-IADL.
8) In the Chinese version of the study, the validity of the scale was examined by factor analysis, which identified nine content items.
9) The correlations between scale scores and disability levels in the Korean version of Lawton-IADL were -0.67 (p<0.001) for men and -0.58 (p<0.001) for women.
10) The correlations between the Spanish version compared to the BI, Medical Outcome Study (MOS) 12-items short form, Western Ontario and McMaster Universities Arthritis Index (WOMAC) short form, and Quick DASH (Disabilities of the Arm, Shoulder, and Hand) scales were above 0.40.
2) In the Persian version, Mehreban et al.
11) reported a correlation coefficient of -0.688 for the comparison of the scale with the Functional Assessment Staging test. Considering the results of other studies, the target older population, and the scale contents, the FIS, BI and Katz Index were considered appropriate to assess the validity of the Lawton-IADL. The total score of the scale showed excellent correlations with other indexes such as FIS (0.850), BI (0.843), and Katz Index (0.896). These findings indicate that IADL are related to the level of independence and BADL in older adults. The very high correlations between the Lawton-IADL and the FIS, BI and Katz Index supports that this scale is a valid tool for use in older populations.
Apart from the original scale and other version studies, the present study investigated the correlation of each Lawton-IADL subheading with another subheading with similar content. We observed that the Lawton-IADL was highly correlated with Katz Index subheadings similar to shopping, cooking, housekeeping, laundry, and transportation, and was poorly correlated with the subheading of handling finances. Although activities of daily living such as transportation, housekeeping, and food preparation are associated with physical health and independence, the handling of finances may be affected by mental health, educational level, and cognitive skill factors. In other words, it is not surprising that handling finances, an IADL, was not highly correlated with the Katz Index, a marker of activities of daily living.
We observed moderate correlations between the VAS scores and subheadings of the ability to use a telephone and medication. However, we obtained different results in the other subheadings, with a higher correlation using the Katz Index. The reason for this difference was that the Lawton-IADL subheadings included verbal and singular results, while the VAS score yielded quantitative and frequently plural results.
The high values, indicators of the validity and reliability of the Lawton-IADL, may be attributed to the fact that this scale is clear, feasible, and has a low scoring range.
Our study has some limitations. The study population comprised people from the same geriatric rehabilitation unit and nursing home environment, which may have affected the generalizability of the data. Including participants from two different cities (Mugla and Ankara) may also have affected the results, as participants from different cities may exhibit different sociodemographic characteristics. Also, the Lawton-IADL may not be sensitive enough to detect minor changes in IADL due to its scoring system. However, Yasuda et al.
32) compared the strengths of the scale to those of the Lawton-IADL for evaluating activities of daily living and reported that the strength of the scale was the ability to measure more complex function levels, increased sensitivity to detect serious dysfunctions since the person is likely to lose complex activities before simple activities, and more predictable detection in patients than that with an external performance assessment.
In conclusion, the Turkish version of the Lawton-IADL, which is widely used for the evaluation of IADL, is a valid and reliable scale for use in Turkish older adults.