Pilot testing of the pre final version of the I-OPQOL-35
The pre-final version of the I-OPQOL-35 was pretested on 30 older adults who were taken through cognitive debriefing interview. These participants had at least 95% of clarity and ease of understanding of most of the items except for three items (2, 4, & 24). These items were considered and modified at the second panel meeting based on the more suitable option for it. The 2nd item (I am happy much of the time) was modified from “A na m enwekarị obi aṅụrị” to “A na m enwe obi aṅụri ọtụtụ oge. The 4th item (Life gets me down) was modified from “Ndụ na-akụtu mmụọ m” to “ndụ kụturu m ala”, and finally the 24th item (I tend to look on the bright side), from “A na m enwe aṅụrị na nchekwube na agbanyeghị ịhe ọ bụla” to “A na m elegara anya na ihe ọma dị n’ọnọdụ niile”. No further modifications were made on the questionnaire, and hence, the final Igbo version of the OPQOL-35 was produced.
Validation of the I-OPQOL-35
Socio demographic profile of the participants
The socio demographic characteristics of the respondents are presented in Table 1. A total of 115 (male 45.2%, female 54.8%) older adult respondents participated in the psychometric testing. Majority of the participants (83.5%) were still married; 70.4% had at least a secondary education; 19.1% were retirees; while 40.1% were civil/public servants.
Validity and reliability analysis of the I-OPQOL-35
Concurrent validity
The coefficients of correlations between corresponding domain and total scores on the E-OPQOL-35 and the I-OPQOL-35 were all excellent and significant (rho=0.92-1.00; p<0.001), with the “religion and culture domain” and “total” scores having the least and highest correlation coefficients respectively. This indicates excellent concurrent validity in all the total and domain scores on the I-OPQOL-35 (Table 2), thus suggesting that the E-OPQOL-35 and the I-OPQOL-35 can produce equivalent scores when administered to the same individuals. The scatter plots of the correlation between the total scores on the I-OPQOL-35 and the E-OPQOL-35 is shown in Fig 1. The Bland-Altman plot pictorially illustrates the total scores on the I-OPQOL-35 and the E-OPQOL-35, revealing homoscedasticity of both results (Fig. 2). A comparison between the domain scores on the E-OPQOL-35 and the I-OPQOL-35 using the Mann-Whitney U test showed no significant difference (p>0.05) in any of the domains, thus indicating the linguistic and conceptual equivalence of the two versions (Table 3).
Internal consistency
The Cronbach’s alpha for the domain-to-total correlation on the I-OPQOL-35 was 0.78. This value shows that the internal consistency was good, thus indicating that the items on the I-OPQOL-35 measure different aspects of the same construct. The standard error of mean and minimum detectable difference values for the domain and total scores on the I-OPQOL-35 are shown on Table 4. The MDD values ranged from 0.25 (Religion and Culture domain) to 4.82 (total score). Religion and culture domain and the total had the lowest and highest SEM scores respectively; thus, giving a better understanding of the responsiveness of the domain and total scores on the scale.
Structural validity of the I-OPQOL-35
The structural validity of the I-OPQOL-35 was performed using the Principal Component Analysis (PCA). Prior to performing PCA, the suitability of the data for factor analysis was assessed. The Kaiser-Meyer-Olkin (KMO) value of 0.833 exceeded 0.6, which is the recommended value [35], while the Barlett’s test of sphericity reached statistical significance (X2 = 2794.665; p < 0.001), thus supporting reasonable factorability of the data.
The PCA revealed the presence of nine factors with eigenvalues exceeding 1, describing 34.088, 8.499, 6.186, 5.960, 4.335, 3.670, 3.321, 3.104, and 2.940 of the variances respectively. The nine component solution thus explained a total of 72.103% of the variances. Other factors had eigen values less than 1 (Table 5). The extraction is based on Kaiser criterion i.e., only factors that had eigen values greater than 1 are retained. Scree plot also illustrated the presence of these nine factors (Fig. 3). All the 35 scale items had communality values that were >0.3 which indicated that all the items fit well with one another, and are to be retained for use on the scale. Communality values that are <0.3 might indicate that the items do not share common variances with the other items loading on the same component (Table 6).
Table 1: Socio-demographic profiles of study participants
Parameters Class Frequency Percentage (%)
Gender Male 52 45.2
Female 63 54.8
Marital status Married 96 83.5
Widowed 19 16.6
Occupation Unemployed 3 2.6
Farming 8 7
Civil/public service 46 40.1
Retirees 22 19.1
Artisans 8 6.9
Trading 28 24.3
Educational attainment No formal education 2 1.7
Primary 32 27.9
Secondary 35 30.4
Tertiary 46 40.0
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Table 2: Spearman Rank Order Correlation between the domains in the E-OPQOL-35 and I-OPQOL-35
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Domains rho p Rating
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Life overall 0.95 <0.001 Excellent
Health 0.96 <0.001 Excellent
Social relationships 0.99 <0.001 Excellent
Independence control 0.98 <0.001 Excellent
Home and neighbourhood 0.99 <0.001 Excellent
Psychological and emotional 0.98 <0.001 Excellent
Financial circumstances 0.99 <0.001 Excellent
Religion and culture 0.92 <0.001 Excellent
Total 1.00 <0.001 Excellent
Key:
E-OPQOL-35: English version of the Older People’s Quality of Life questionnaire
I-OPQOL-35: Igbo version of the Older People’s Quality of Life questionnaire
Table 3: Mann Whitney U test comparing scores on both the E-OPQOL-35 and I-OPQOL-35 domain
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Variable Mean±SD U P
English Igbo
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Life Overall 8.504±2.6 8.591±2.6 6506.5 0.83
Health 8.296±3.2 8.252±3.2 6543.0 0.89
SRPLS 12.70±4.4 12.63±4.3 6531.0 0.87
ICOLF 9.452±3.5 9.504±3.4 6554.0 0.91
H&N 6.887±2.8 6.913±2.8 6560.5 0.92
P&EW 7.017±2.6 7.174±2.7 6389.0 0.65
FC 10.97±4.5 10.97±4.5 6576.5 0.94
R&C 2.635±0.9 2.609±0.9 6511.0 0.81
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Key:
E-OPQOL-35: English version of the Older People’s Quality of Life questionnaire
I-OPQOL-35: Igbo version of the Older People’s Quality of Life questionnaire
ICOLF: Independence, Control, Over Life and Freedom
SRPLS: Social Relationships, Participation, Leisure and Social Activities
FC: Financial Circumstances; R&C: Religion and Culture
P&EW: Psychological and Emotional Well Being; H&N: Home and Neighbourhood
Table 4: Standard error of mean and minimal detectable difference of the domain and total scores on the I-OPQOL-35
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Variable SEM MDD
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Life Overall 0.24 0.67
Health 0.30 0.83
SRPLS 0.40 1.11
ICOLF 0.32 0.89
H&N 0.26 0.72
P&EW 0.25 0.69
FC 0.42 1.16
R&C 0.09 0.25
Total 1.74 4.82
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Key:
SEM: Standard error of mean; MDD: Minimal detectable difference
E-OPQOL-35: English version of the Older People’s Quality of Life questionnaire
I-OPQOL-35: Igbo version of the Older People’s Quality of Life questionnaire
ICOLF: Independence, Control, Over Life and Freedom
SRPLS: Social Relationships, Participation, Leisure and Social Activities
FC: Financial Circumstances; R&C: Religion and Culture
P&EW: Psychological and Emotional Well Being
H&N: Home and Neighbourhood
Table 5: Principal Component analysis of the I-OPQOL-35
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Components Initial Eigen values Decision Variances% Cumulative%
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C1 11.931 Accepted 34.088 34.088
C2 2.975 Accepted 8.499 42.587
C3 2.165 Accepted 6.186 48.773
C4 2.086 Accepted 5.960 54.734
C5 1.517 Accepted 4.335 59.069
C6 1.284 Accepted 3.670 62.739
C7 1.162 Accepted 3.321 66.059
C8 1.087 Accepted 3.104 69.164
C9 1.029 Accepted 2.940 72.104
C10 0.993 Rejected 2.836 74.940
C11 0.822 Rejected 2.349 77.289
C12 0.798 Rejected 2.280 79.569
C13 0.734 Rejected 2.097 81.665
C14 0.706 Rejected 2.017 83.683
C15 0.615 Rejected 1.758 85.441
C16 0.611 Rejected 1.744 87.186
C17 0.528 Rejected 1.510 88.695
C18 0.471 Rejected 1.347 90.042
C19 0.398 Rejected 1.137 91.179
C20 0.363 Rejected 1.037 92.216
C21 0.351 Rejected 1.003 93.219
C22 0.339 Rejected 0.970 94.189
C23 0.291 Rejected 0.832 95.021
C24 0.259 Rejected 0.741 95.762
C25 0.223 Rejected 0.638 96.400
C26 0.189 Rejected 0.540 96.940
C27 0.181 Rejected 0.518 97.459
C28 0.172 Rejected 0.490 97.949
C29 0.162 Rejected 0.463 98.412
C30 0.141 Rejected 0.404 98.816
C31 0.128 Rejected 0.367 99.183
C32 0.105 Rejected 0.299 99.482
C33 0.095 Rejected 0.270 99.752
C34 0.056 Rejected 0.160 99.912
C35 0.031 Rejected 0.088 100.000
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KEY: I-OPQOL-35: Igbo version of the Older People’s Quality of Life questionnaire
Table 6: Communalities of the items on the I-OPQOL-15
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Items Initial Extraction
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I-OPQOL1 1.000 0.677
I- OPQOL2 1.000 0.706
I- OPQOL3 1.000 0.653
I- OPQOL4 1.000 0.675
I- OPQOL5 1.000 0.633
I- OPQOL6 1.000 0.728
I- OPQOL7 1.000 0.796
I- OPQOL8 1.000 0.656
I- OPQOL9 1.000 0.676
I- OPQOL10 1.000 0.744
I- OPQOL11 1.000 0.677
I- OPQOL12 1.000 0.893
I- OPQOL13 1.000 0.874
I- OPQOL14 1.000 0.761
I- OPQOL15 1.000 0.771
I- OPQOL16 1.000 0.773
I- OPQOL17 1.000 0.723
I- OPQOL18 1.000 0.645
I- OPQOL19 1.000 0.764
I- OPQOL20 1.000 0.734
I- OPQOL21 1.000 0.685
I- OPQOL22 1.000 0.675
I- OPQOL23 1.000 0.537
I- OPQOL24 1.000 0.671
I- OPQOL25 1.000 0.615
I- OPQOL26 1.000 0.876
I- OPQOL27 1.000 0.883
I- OPQOL28 1.000 0.874
I- OPQOL29 1.000 0.719
I- OPQOL30 1.000 0.739
I- OPQOL31 1.000 0.666
I- OPQOL32 1.000 0.707
I- OPQOL33 1.000 0.732
I- OPQOL34 1.000 0.698
I- OPQOL35 1.000 0.601
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Key: Extraction Method Principal Component Analysis; I- OPQOL-35 Igbo version of the Older People’s Quality of Life questionnaire