International Index of Erectile function (IIEF) among Filipino Men: A Reliability and Validity using Exploratory and Confirmatory Factor Analyses

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International Index of Erectile function (IIEF) among Filipino Men: A Reliability and Validity using Exploratory and Confirmatory Factor Analyses

https://doi.org/10.21203/rs.3.rs-3346379/v1

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The International Index of Erectile Function (IIEF) has emerged as a pivotal instrument for the evaluation of erectile dysfunction (ED) in both clinical and research settings. However, its psychometric properties have not been extensively examined among diverse populations. This study aimed to investigate the validity and reliability of the IIEF among a sample of Filipino men, given the distinct socio-cultural perspectives associated with sexuality and ED in this demographic. A total of N = 1,463 participants, aged 18 years and older, from various regions of the Philippines were enrolled.

Initial evaluations confirmed the internal consistency of the IIEF, with Cronbach's alpha values consistently ranging from .78 to .92 for each of the five domains. For construct validity, exploratory factor analysis (EFA) was first utilized, revealing three-factor structure (sexual intercourse, stimulation, and satisfaction [IIEF-SSS]). Cronbach’s alpha for each IIEF-SSS subscale ranges from .76 to .96. Subsequent confirmatory factor analysis (CFA) provided robust support for this structure, with fit indices suggesting a strong model fit (X² = 252.95, df = 80, X²/ df ratio = 3.16, RMSEA = 0.059, NFI = .97, CFI = .98, IFI= .98, GFI = .95, AGFI = .92).

The results of this comprehensive analysis underscore the IIEF-SSS’ robustness as a psychometric tool, confirming its reliability and validity within a Filipino context. Healthcare providers and researchers in the Philippines can, therefore, employ the IIEF-SSS with confidence when assessing ED. Additionally, the findings illuminate the instrument's cross-cultural adaptability, offering a precedent for its potential application in other diverse settings. Future studies could further delve into the cultural nuances impacting ED and its perception among Filipino men.

Health sciences/Diseases/Urogenital diseases/Erectile dysfunction

Health sciences/Health care/Quality of life

The IIEF is a multidimensional questionnaire used worldwide to assess and evaluate erectile function among men. It measures erection, ejaculation, and orgasmic function, as well as sexual desire and satisfaction. The IIEF was first used in the late 1990’s in a study to evaluate the efficacy of a phosphodiesterase-5 inhibitor called sildenafil. Sildenafil (Viagra) became the first oral medication used to manage erectile dysfunction (Rosen et al., 1997).

The IIEF has been translated and validated into other languages including Spanish (Díaz-Mohedo et al., 2023; Lizarraga-Limousin et al., 2022; Vallejo-Medina et al., 2022), Italian (Galizia et al., 2023), Indonesian (Laksita et al., 2021), German (Kriston et al., 2008), and Chinese (Tang et al., 2018). It has been used as a patient reported outcomes in erection function research since inception in 1997. In addition, the IIEF is the most widely used questionnaire in clinical settings (Neijenhuijs et al., 2019).

The scores for IIEF are determined by answering a 15-item questionnaire which is rated from 0–5 in a Likert-type scale. The total score is added and the highest could be up to 75. The higher the score the better the sexual functioning. The IIEF domains include Erectile Function (EF), Sexual Desire (SD), Orgasmic Function (OF), Intercourse Satisfaction (IS), and Overall Satisfaction (OS) (Rosen et al., 1997). The EF domain is composed of the questions 1–5 and 15, while IS domain is composed of questions 6–8. The questions 9 and 10 make the OF domain, while 11 and 12 composed by SD. OS is composed of questions 13 and 14.

Erectile dysfunction (ED) is the inability of the male penis to initiate and maintain erection for satisfactory sexual activity. It is affected by multifactorial processes including neurological, hormonal, vascular, and psychological. Erectile dysfunction is common among men 40 years old older. Age is the most common factor associated with erectile dysfunction. Furthermore, chronic non-communicable diseases such as cardiovascular, stroke, and metabolic disorders are closely associated with ED.

Erectile dysfunction (ED) serves as a sentinel indicator for not only sexual health but also broader domains of physiological and psychological well-being. While the IIEF's utility is indisputable in diverse contexts, the question of its reliability and validity in specific cultural settings remains paramount. Cultural, societal, and psychological nuances can significantly influence perceptions of sexual health, shaping the way individuals respond to standardized questionnaires. This brings forth the critical query: Is the IIEF universally applicable, or are there intrinsic cultural factors that might alter its structure and interpretation?

The Philippines, with its intricate blend of indigenous, Hispanic, American, and broader Asian influences, offers a unique socio-cultural milieu. Here, masculinity, sexuality, and health perceptions are interwoven with historical, religious, and regional threads (The World Factbook - Philippines, 2023). Provided with these data, it becomes imperative to probe deeper into the reliability and validity of tools like the IIEF. Are the factor structures, as understood in Western or other contexts, consistent among Filipino men? Does the tool maintain its reliability in capturing the nuances of ED in this particular demographic? Furthermore, the result of a recent systematic review conducted to study the properties of IIEF concludes that research to investigate the internal consistency, structural and construct validity including measurement error and responsiveness is needed (Neijenhuijs et al., 2019). Employing exploratory and confirmatory factor analysis (EFA, CFA) offers an empirical pathway to address these needs. These statistical techniques delve into the underlying structure of datasets, validating the number of factors and the loadings of individual items on these factors (Kline, 2023).

This study sought to harness the power of EFA and CFA to assess the reliability and validity of the IIEF among Filipino men, aiming to provide invaluable insights for both clinical practice and academic research within the region.

As part of a larger study to find the prevalence and indicators of ED among Filipino men, a cross-sectional study was conducted to find evidence of validity and reliability of the IIEF. After IRB approval, recruitment and data collection was conducted online using social media platform (e.g, Facebook). It was explicitly advertised that participation in this study is voluntary and that there is no compensation offered. The participants are informed that they are free to withdraw at any time without penalty. The inclusion criteria are (a) Filipino men 18 years and older, (b) no previous history of penile deformity and surgery, and (c) able to complete online questionnaire. The SPSS was used for Cronbach alpha, descriptive statistics, and EFA. LISREL software was used for the CFA.

A total of N = 1,463 Filipino men participated in the study. The data was reviewed and a listwise deletion of incomplete responses was conducted. After listwise deletion of incomplete responses, a total of N = 620 was included in data analysis.

Participant Characteristics

The participants were composed of Filipino men 18-78 years old (M= 43.21, SD = 17.87) who were mostly college graduates (35.9%), single/never married (58.3%), and were heterosexual/straight (46.1%). Furthermore, the participants were 55.2% young adult (18-39 years old), 35.6% middle-aged (40-64 years old), and 9.2% seniors (65 years and older). The result of the prevalence study is published elsewhere.

Internal Consistency

The internal consistency reliability was conducted by calculating the Cronbach alpha. The result shows that IIEF has an overall Cronbach alpha of .94. The Cronbach alphas for each IIEF subscales including EF, IS, OF, SD, and OS are .90, .92, .91, .78, and .83, respectively.

Exploratory Factor Analysis

The EFA was conducted using a principal component analysis (PCA) extraction method with a varimax rotation. The Kaiser-Meyer-Olkin (KMO) measure verified the sampling adequacy for the analysis, KMO = .93 which is above the recommended value of 0.6. Bartlett’s test of sphericity X² (105) = 8393.50, p < .001, indicated that correlations between items were sufficiently large for PCA.

An initial analysis was run to obtain eigenvalues for each component in the data. Three components had eigenvalues over Kaiser’s criterion of 1 and in combination explained 74% of the variance. Table 1 presents the initial eigenvalues and percent of variance for each component.

The scree plot demonstrated inflections that justified retaining all three components. Component matrix after rotation indicated the following distribution: Component I: questions 1, 3, 4, 5, 6, 7, and 8; Component II: questions 2, 9, 10, 11, and 12; Component III: questions 13, 14, and 15. The factor coefficients ranges from .66 to .88.

Reliability analysis was conducted on each of the components derived from the EFA. Cronbach’s alpha for the items in each component were .96, .85, .76, respectively. The factor loadings and Cronbach’s alpha are presented in Table 2.

The three latent factors were named according to the theme of items loaded on each factor. These include erections during Sexual Intercourse, upon Stimulation, and Satisfaction for components 1, 2, and 3, respectively.

Confirmatory Factor Analysis

To determine the best-fitting factor structure for the IIEF among the sample of Filipino men, three models were tested: a unidimensional model, three-factor model provided by the EFA in this current study, and the original five-factor IIEF. Table 3 shows the details of the goodness-of-fit index for each model.

The CFA result demonstrates that the three-factor model is the best fitting model for the data. The three-factor model goodness-of-fit indices shows X² = 252.95, df = 80, X²/ df ratio = 3.16, RMSEA = 0.059, NFI = .97, CFI = .98, IFI= .98, GFI = .95, AGFI = .92. While an initial CFA failed to support a goodness-of-fit index for the three-factor model, model modification was performed following the modification index. The path for components 1 and question 2; and component 2 and question 1 were freed. Furthermore, freeing the correlation of errors on the measurement model including items 1 and 2; items 3 and 4; 9 and 10; 11 and 12; and 12 and 15 provided a lower chi-square value. The standardized solutions for the three-factor model are presented in Figure 1.

This study is the first to find evidence of reliability and validity of IIEF using EFA and CFA among Filipino men. The EFA provided a novel three-factor model for IIEF. The internal consistency supports the excellent reliability of each subscale with Cronbach’s alphas ranging from .76 to .96. The subscales were termed according to the theme emerged from the convergence of intercorrelated items into each factor. The subscales were termed measuring erections according to Sexual Intercourse, Stimulation, and Satisfaction. This three-factor IIEF may be called the IIEF-SSS. Furthermore, the overall Cronbach’s alpha for the IIEF-SSS presents an excellent internal consistency, .94. This excellent internal reliability is consistent with previous studies’ Cronbach’s alpha ranging from .73 to .96 (Díaz-Mohedo et al., 2023; Gonzáles et al., 2013; Quinta Gomes & Nobre, 2012). While the nature of cross-sectional study collects data in one period of time, a test-retest reliability in the future research will provide further evidence of the IIEF-SSS’s reliability.

Likewise, the CFA demonstrates that the three-factor model is the best fitting-model for IIEF among Filipino men. The CFA supports that the latent variables elicited by the EFA are valid structural component of the IIEF-SSS. Provided with the goodness-of-fit indices, the manifest variables along with measurement errors were estimated. The IIEF-SSS provides three factors measuring erection during sexual intercourse, upon stimulation, and satisfaction. Moreover, the CFA revealed items which are multidimensional measuring two factors at once. These items are the IIEF questions 1 (How often were you able to get an erection during sexual activity?), and 2 (When you had erections with sexual stimulation, how often were your erections hard enough for penetration?) which measure erection on sexual intercourse and stimulation at the same time. Further research is needed to examine the effects of these two items on both factors in future study. Nonetheless, the CFA provided an evidence of construct validity for the IIEF-SSS.

While there is wide range of ED prevalence in Asian countries (2–82%) (Ho et al., 2011; Lewis, 2011; Park et al., 2011) the Philippines ranked among Asian countries with the most men suffering from ED (33–65%) next to Japan (13–81%), and Thailand (29–65%) (Park et al., 2011). This current study reveals that ED prevalence among Filipino men is at 78.8% which shows 15% increase from 2011. The concerning increase in prevalence of ED needs to be addressed. While sex and ED remain a taboo in Asian countries, particularly in the Philippines, early diagnosis and management is warranted as ED is significantly associated with cardiovascular diseases (Mostafaei et al., 2021) which top the ten main causes of death in the Philippines in 2022 (2022 Causes of Deaths in the Philippines (Preliminary as of 31 July 2022), 2022). Furthermore, the risk for ED increases with age (MacDonald & Burnett, 2021). The IIEF-SSS will be a useful tool to screen Filipino men for ED.

Strengths and Limitations

A significant advantage of this study is its expansive participant sample size. Yet, since the recruitment process was exclusively online, men who might have favored a traditional paper-pencil format—potentially offering differing insights—weren't captured in this sample. The representation of older participants was notably limited. This can be attributed to the lesser online engagement of senior men compared to their younger counterparts. For a more comprehensive understanding of the IIEF-SSS among the senior demographic, it would be beneficial to employ alternative data collection methods, such as face-to-face interviews. The employed statistical tools, including EFA and CFA, are intricate; hence, careful consideration should be given when deducing the broader applicability of the findings. Subsequent studies should consider incorporating test-retest reliability to bolster the instrument's dependability. Implementing the IIEF-SSS questionnaire in both research and clinical environments to evaluate ED among Filipino men could shed more light on its consistent reliability and validity.

The three-factor model of the IIEF stands as a valid and reliable instrument to assess and evaluate erectile function and the management of ED in the Filipino male population. Given that ED is a notable risk factor for cardiovascular diseases, employing the IIEF-SSS can be instrumental in the early detection of ED among Filipino men. For both research and clinical environments, the IIEF-SSS proves reliability and validity in this study.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request. Specific conditions for data access and sharing will be determined on a case-by-case basis to ensure confidentiality and ethical considerations are met. For further information, please contact Sagie De Guzman at [email protected]

Acknowledgements

The author acknowledges the voluntary participation of Filipino men.

Ethical Approval

The Institutional Review Board of Providence Saint John’s Cancer and Research Institute approved this study.

Competing Interest

The author declares no competing interest.

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Table 1. Eigenvalues, Percentages of Variance, and Cumulative Percentages for Factors of the 15-Item International Index of Erectile Function (IIEF).

Factor

Eigenvalue

% of Variance

Cumulative %

8.49

1.59

1.06

56.58

10.62

7.08

56.58

67.20

74.28

Table 2. Factor Loadings for Varimax Orthogonal Three-Factor Solution for the Items of the Item International Index of Erectile Function (IIEF)

Item

Factor Loading

Factor 1: Cronbach alpha .96

IIEF5. During sexual intercourse, how difficult was it to maintain your erection to completion of intercourse?

IIEF4. During sexual intercourse, how often were you able to maintain your erection after you had penetrated (entered) your partner?

IIEF3. When you attempted sexual intercourse, how often were you able to penetrate (enter) your partner?

IIEF8. How much have you enjoyed sexual intercourse?

IIEF7. When you attempted sexual intercourse, how often was it satisfactory for you?

IIEF6. How many times have you attempted sexual intercourse?

IIEF1. How often were you able to get an erection during sexual activity?

.88

.87

.74

.59

Factor 2: Cronbach alpha .85

IIEF11. How often have you felt desire?

IIEF10. When you had sexual stimulation or intercourse, how often did you have the feeling of orgasm or climax?

IIEF9. When you had sexual stimulation or intercourse, how often did you ejaculate?

IIEF12. How would you rate your level of sexual desire?

IIEF2. When you had erections with sexual stimulation, how often were your erections hard enough for penetration?

.76

.73

.72

.69

.57

Factor 3: Cronbach alpha .76

IIEF13. How satisfied have you been with your overall sex life?

IIEF14. How satisfied have you been with your sexual relationship with your partner?

IIEF15. How do you rate your confidence that you could get and keep an erection?

.75

.74

.66

Note: The overall Cronbach alpha for the three-factor IIEF is .94

Table 3. Goodness-of-Fit Indices of Three Models for the International Index of Erectile Function (IIEF) (N = 620)

Model	df	X²	X²/df	NFI	CFI	IFI	GFI	AGFI	RMSEA
Single Factor	90	1976.29	21.95	.77	.78	.78	.66	.55	.184
3-Factor	80	252.95	3.16	.97	.98	.98	.95	.92	.059
5-Factor	80	827.75	10.34	.90	.91	.91	.83	.75	.123

Note: df = degree of freedom; X²= Chi square; NFI = Normed Fit Index; IFI = Incremental Fit Index; CFI = Comparative Fit Index; GFI = Goodness-of-Fit Index; AGFI = Adjusted Goodness of Fit Index; RMSEA = Root Mean Square Error of Approximation. Bold text indicates the best-fitting model.

There is NO conflict of interest to disclose.

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International Index of Erectile function (IIEF) among Filipino Men: A Reliability and Validity using Exploratory and Confirmatory Factor Analyses

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