Different factor loadings for SF36: The Strong Heart Study and the National Survey of Functional Health Status

Meniere Disease treated with transcutaneous auricular vagus nerve stimulation combined with betahistine Mesylate: A randomized controlled trial

BACKGROUND

Meniere Disease is a clinical condition defined by hearing loss, tinnitus, and aural fullness symptoms, there are currently no any medications approved for its treatment.

OBJECTIVE

To determine whether taVNS as an adjunctive therapy could relieve symptoms and improve the quality of life in patients with Meniere disease.

METHODS

In this Single-center, single blind, randomized trial, participants were assigned to transcutaneous auricular vagus nerve stimulation (taVNS) group and sham taVNS group. The primary outcome measures comprised Tinnitus Handicap Inventory, Dizziness Handicap Inventory, Pure Tone Auditory, Visual analogue scale of aural fullness. Secondary outcome measures comprised the 36-Item Short Form Health Survey, video head impulse test, and the caloric test.

RESULTS

After 12 weeks, the THI (-11.00, 95%CI, -14.87 to -7.13; P < 0.001), DHI (-47.26, 95%CI, -50.23 to -44.29; P < 0.001), VAS of aural fullness (-2.22, 95%CI, -2.95 to -1.49; P<0.01), and Pure Tone Thresholds (-7.07, 95%CI, -9.07 to -5.06; P<0.001) were significantly differed between the two groups. In addition, SF36(14.72, 95%CI, 11.06 to 18.39; P < 0.001), vHIT (RD, 0.26, 95 % CI, -0.44 to -0.08, RR, 0.43, 95 % CI, 0.22 to 0.83, P < 0.01), and the caloric test (RD, -0.24, 95 % CI, -0.43 to -0.04, RR, 0.66, 95 % CI, 0.44 to 0.95, P = 0.02) have significant difference between two group, respectively.

CONCLUSIONS

These findings suggest that taVNS combined with Betahistine Mesylate relieve symptoms and improve the quality of life for patients with Meniere Disease. taVNS can be considered an adjunctive therapy in treatment of Meniere Disease.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05328895.

Psychological and social support associations with mortality and cardiovascular disease in middle-aged American Indians: the Strong Heart Study

PURPOSE

Our study examined psychosocial risk and protective features affecting cardiovascular and mortality disparities in American Indians, including stress, anger, cynicism, trauma, depression, quality of life, and social support.

METHODS

The Strong Heart Family Study cohort recruited American Indian adults from 12 communities over 3 regions in 2001-2003 (N = 2786). Psychosocial measures included Cohen Perceived Stress, Spielberger Anger Expression, Cook-Medley cynicism subscale, symptoms of post-traumatic stress disorder, Centers for Epidemiologic Studies Depression scale, Short Form 12-a quality of life scale, and the Social Support and Social Undermining scale. Cardiovascular events and all-cause mortality were evaluated by surveillance and physician adjudication through 2017.

RESULTS

Participants were middle-aged, 40% male, with mean 12 years formal education. Depression symptoms were correlated with anger, cynicism, poor quality of life, isolation, criticism; better social support was correlated with lower cynicism, anger, and trauma. Adjusted time-to-event regressions found that depression, (poor) quality of life, and social isolation scores formed higher risk for mortality and cardiovascular events, and social support was associated with lower risk. Social support partially explained risk associations in causal mediation analyses.

CONCLUSION

Altogether, our findings suggest that social support is associated with better mood and quality of life; and lower cynicism, stress, and disease risk-even when said risk may be increased by comorbidities. Future research should examine whether enhancing social support can prospectively reduce risk, as an efficient, cost-effective intervention opportunity that may be enacted at the community level.

Psychometric properties of Short Form-36 Health Survey, EuroQol 5-dimensions, and Hospital Anxiety and Depression Scale in patients with chronic pain

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This large-sample item response theory-based evaluation assessed the measurement properties of SF-36, EQ-5D, and hospital anxiety and depression scale for chronic pain patients in clinical settings.

Recent research has highlighted a need for the psychometric evaluation of instruments targeting core domains of the pain experience in chronic pain populations. In this study, the measurement properties of Short Form-36 Health Survey (SF-36),EuroQol 5-dimensions (EQ-5D) and Hospital Anxiety and Depression Scale (HADS) were analyzed within the item response-theory framework based on data from 35,908 patients. To assess the structural validity of these instruments, the empirical representations of several conceptually substantiated latent structures were compared in a cross-validation procedure. The most structurally sound representations were selected from each questionnaire and their internal consistency reliability computed as a summary of their precision. Finally, questionnaire scores were correlated with each other to evaluate their convergent and discriminant validity. Our results supported that SF-36 is an acceptable measure of 2 independent constructs of physical and mental health. By contrast, although the approach to summarize the health-related quality of life construct of EQ-5D as a unidimensional score was valid, its low reliability rendered practical model implementation of doubtful utility. Finally, rather than being separated into 2 subscales of anxiety and depression, HADS was a valid and reliable measure of overall emotional distress. In support of convergent and discriminant validity, correlations between questionnaires showed that theoretically similar traits were highly associated, whereas unrelated traits were not. Our models can be applied to score SF-36 and HADS in chronic pain patients, but we recommend against using the EQ-5D model due to its low reliability. These results are useful for researchers and clinicians involved in chronic pain populations because questionnaires' properties determine their discriminating ability in patient status assessment.

The health-related quality of life of Indigenous populations: a global systematic review

PURPOSE

Indigenous conceptions of health have been shown to differ from that of their non-Indigenous counterparts. As a result, there remains uncertainty over the appropriateness and value of using existing health-related quality-of-life (HRQoL) instruments in Indigenous communities. The objective of this review was to identify studies that either measure the HRQoL of an Indigenous population or validated a measure used to elicit the HRQoL in an Indigenous population.

METHODS

A systematic review of the published literature was conducted to (1) investigate the extent to which HRQoL instruments are used in Indigenous populations; (2) to identify which instruments have been validated in which populations; and (3) to identify which instruments have been tailored for use with Indigenous populations.

RESULTS

Forty-one studies were included in the review. Only three of the 41 studies utilised Indigenous-specific instruments. The remainder (38 studies) utilised generic population or disease-specific instruments. Four studies found specific HRQoL instruments to be valid in these populations and 32 estimated the HRQoL of an Indigenous population. The limited examples of Indigenous-specific instruments highlighted the potential importance to the HRQoL of these populations of domains that lie outside of traditional measures including social and community domains as well as domains relating to culture, diet and land use on top of more traditional HRQoL domains.

CONCLUSION

Ensuring that the HRQoL of Indigenous populations is being appropriately measured is vital to prioritising available resources to the most effective interventions. HRQoL instruments present an opportunity to directly elicit and incorporate Indigenous preferences and conceptions of health into these decisions. Further work is required in the field to ensure that this potential is realised.

Detecting short-term change and variation in health-related quality of life: within- and between-person factor structure of the SF-36 health survey

Background

A major goal of much aging-related research and geriatric medicine is to identify early changes in health and functioning before serious limitations develop. To this end, regular collection of patient-reported outcome measure (PROMs) in a clinical setting may be useful to identify and monitor these changes. However, existing PROMs were not designed for repeated administration and are more commonly used as one-time screening tools; as such, their ability to detect variation and measurement properties when administered repeatedly remain unknown. In this study we evaluated the potential of the RAND SF-36 Health Survey as a repeated-use PROM by examining its measurement properties when modified for administration over multiple occasions.

Methods

To distinguish between-person (i.e., average) from within-person (i.e., occasion) levels, the SF-36 Health Survey was completed by a sample of older adults (N = 122, M_age = 66.28 years) daily for seven consecutive days. Multilevel confirmatory factor analysis (CFA) was employed to investigate the factor structure at both levels for two- and eight-factor solutions.

Results

Multilevel CFA models revealed that the correlated eight-factor solution provided better model fit than the two-factor solution at both the between-person and within-person levels. Overall model fit for the SF-36 Health Survey administered daily was not substantially different from standard survey administration, though both were below optimal levels as reported in the literature. However, individual subscales did demonstrate good reliability.

Conclusions

Many of the subscales of the modified SF-36 for repeated daily assessment were found to be sufficiently reliable for use in repeated measurement designs incorporating PROMs, though the overall scale may not be optimal. We encourage future work to investigate the utility of the subscales in specific contexts, as well as the measurement properties of other existing PROMs when administered in a repeated measures design. The development and integration of new measures for this purpose may ultimately be necessary.

Construct validity of the SF-12 among American Indian and Alaska Native people using two known scoring methods

OBJECTIVE

This study evaluated the construct validity of the 12-Item Short Form Survey Instrument (SF-12) in a cohort of American Indian and Alaska Native (AIAN) people. We evaluated two scoring methods to determine their utility in this population.

METHODS

Participants (N = 11,127) were aged 18 and older, self-identified as AIAN, and had complete SF-12 interview data. Physical and mental health summary scores were calculated using traditional SF-12 (PCS12 and MCS12) and RAND-12 (PHC and MHC) scoring methods.

RESULTS

Women scored lower than men on the PHC, PCS12, MHC, and MCS12, as did those with more medical conditions versus none. Those aged 55 and older scored lower on the PHC and PCS12 than younger people. There was no difference in the mean MCS12 score by age and for those 31-55 and aged older than 55 for the MHC.

CONCLUSIONS

This study demonstrates the construct validity of the PCS12/MCS12 and PHC/MHC in a cohort of AIAN people.

Validation of the SF-36 in patients with endometriosis

Objectives

Endometriosis presents with significant pain as the most common symptom. Generic health measures can allow comparisons across diseases or populations. However, the Medical Outcomes Study Short Form 36 (SF-36) has not been validated for this disease. The goal of this study was to validate the SF-36 (version 2) for endometriosis.

Methods

Using data from two clinical trials (N = 252 and 198) of treatment for endometriosis, a full complement of psychometric analyses was performed. Additional instruments included a pain visual analog scale (VAS); a physician-completed questionnaire based on patient interview (modified Biberoglu and Behrman—B&B); clinical global impression of change (CGI-C); and patient satisfaction with treatment.

Results

Bodily pain (BP) and the Physical Component Summary Score (PCS) were correlated with the pain VAS at baseline and over time and the B&B at baseline and end of study. In addition, those who had the greatest change in BP and PCS also reported the greatest change on CGI-C and patient satisfaction with treatment. Other subscales showed smaller, but significant, correlations with change in the pain VAS, CGI-C, and patient satisfaction with treatment.

Conclusions

The SF-36—particularly BP and the PCS—appears to be a valid and responsive measure for endometriosis and its treatment.

A review of the measurement properties of the 36-item short-form health survey (SF-36) to determine its suitability for use in an alcohol-dependent population

A psychometric evaluation of the 36-item short-form health survey (SF-36) was undertaken in contemporary studies to assess its suitability for use in an alcohol-dependent population. Three criteria were used to try and determine this: factor analysis, internal consistency reliability and test-retest reliability. Factor analysis revealed that it is mainly consistent with a bidimensional model, internal consistency reliability showed that it consistently provided scores above the recommended threshold and test-retest reliability of the SF-36 highlights that it too provided higher than suggested scores. A conclusion was reached recommending the SF-36 as a reliable screening tool in an alcohol-dependent population, but this is given in caution as no studies were found analysing the instrument in this population.

Assessment of elder mistreatment in two American Indian samples: psychometric characteristics of the HS-EAST and the Native Elder Life-Financial Exploitation and -Neglect measures

Although elder mistreatment among ethnic minorities is increasingly gaining attention, our empirical knowledge of this phenomenon among American Indians remains quite limited, especially with respect to measurement. The Shielding American Indian Elders (SAIE) Project used a collaborative approach to explore culturally informed measurement of elder mistreatment in two American Indian elder samples (a Northern Plains reservation and a South Central metropolitan area). The project sought to investigate the performance characteristics of the commonly used Hwalek-Sengstock Elder Abuse Screening Test (HS-EAST), as well as to examine the psychometric properties of a new measure developed to capture culturally salient aspects of mistreatment in American Indian contexts--the Native Elder Life Scale (NELS). Using methods and samples comparable to those in the literature, the HS-EAST performed adequately in these Native samples. The NELS also shows promise for use with this population and assesses different aspects of elder mistreatment than does the HS-EAST.

Social relationships as a major determinant in the valuation of health states

PURPOSE

To empirically determine the impact of the capacity to sustain social relationships on valuing health states.

METHODS

68 clinical experts conducted a health state valuation exercise in five sites using pairwise comparison, ranking, and person trade-off as elicitation methods. 23,840 pairwise comparisons of a total of 379 health states were analyzed by conditional logistic regression.

RESULTS

Social relationships had a clear monotonic association with perceived disability: the more limited the capacity to sustain social relationships, the more disabling the resulting health state valuations. The highest level of limitations with respect to social relationships was associated with slightly lower impact on health state valuations compared to the highest level of limitations in physical functioning.

CONCLUSIONS

Social relationships showed an independent contribution to health state valuations and should be included in health state measures.

The increased cost of medical services for people diagnosed with primary open-angle glaucoma: a decision analytic approach

PURPOSE

Glaucoma accounts for more than 11% of all cases of blindness in the United States, but there have been few studies of economic impact. We examine incremental cost of primary open-angle glaucoma considering both visual and nonvisual medical costs over a lifetime of glaucoma.

DESIGN

A decision analytic approach taking the payor's perspective with microsimulation estimation.

METHODS

We constructed a Markov model to replicate health events over the remaining lifetime of someone newly diagnosed with glaucoma. Costs of this group were compared with those estimated for a control group without glaucoma. The cost of management of glaucoma (including medications) before the onset of visual impairment was not considered. The model was populated with probability data estimated from Medicare claims data (1999 through 2005). Cost of nonocular medications and nursing home use was estimated from California Medicare claims, and all other costs were estimated from Medicare claims data.

RESULTS

We found modest differences in the incidence of comorbid conditions and health service use between people with glaucoma and the control group. Over their expected lifetime, the cost of care for people with primary open-angle glaucoma was higher than that of people without primary open-angle glaucoma by $1688 or approximately $137 per year.

CONCLUSIONS

Among Medicare beneficiaries, glaucoma diagnosis not found to be associated with significant risk of comorbidities before development of visual impairment. Further study is necessary to consider the impact of glaucoma on quality of life, as well as aspects of physical and visual function not captured in this claims-based analysis.

Dimensionality and summary measures of the SF-36 v1.6: comparison of scale- and item-based approach across ECRHS II adults population

OBJECTIVES

The objective of this study was twofold: 1) to confirm the hypothetical eight scales and two-component summaries of the questionnaire Short Form 36 Health Survey (SF-36), and 2) to evaluate the performance of two alternative measures to the original physical component summary (PCS) and mental component summary (MCS).

METHODS

We performed principal component analysis (PCA) based on 35 items, after optimal scaling via multiple correspondence analysis (MCA), and subsequently on eight scales, after standard summative scoring. Item-based summary measures were planned. Data from the European Community Respiratory Health Survey II follow-up of 8854 subjects from 25 centers were analyzed to cross-validate the original and the novel PCS and MCS.

RESULTS

Overall, the scale- and item-based comparison indicated that the SF-36 scales and summaries meet the supposed dimensionality. However, vitality, social functioning, and general health items did not fit data optimally. The novel measures, derived a posteriori by unit-rule from an oblique (correlated) MCA/PCA solution, are simple item sums or weighted scale sums where the weights are the raw scale ranges. These item-based scores yielded consistent scale-summary results for outliers profiles, with an expected known-group differences validity.

CONCLUSIONS

We were able to confirm the hypothesized dimensionality of eight scales and two summaries of the SF-36. The alternative scoring reaches at least the same required standards of the original scoring. In addition, it can reduce the item-scale inconsistencies without loss of predictive validity.

Factorial structure and cross-cultural invariance of the Oral Impacts on Daily Performances

The issue of cross-cultural construct validation and measurement invariance of the Oral Impacts on Daily Performances (OIDP) questionnaire is important. Using confirmatory factor analysis (CFA), this study evaluated a proposed three-factor structure of the OIDP questionnaire in Tanzanian adolescents and adults and assessed whether this model would be replicated in Ugandan adolescents. Between 2004 and 2007, OIDP data were collected from 1,601 Tanzanian adolescents, 1,031 Tanzanian adults, and 1,146 Ugandan adolescents. Model generation analysis was restricted to Tanzanian adolescents, and the model achieved was tested, without modification, in Tanzanian adults and in Ugandan adolescents. A modified three-factor solution with cross-loadings improved the fit of the OIDP model to the data compared with a one-factor model and the original three-factor model within the Tanzanian [comparative fit index (CFI) = 0.99] and Ugandan (CFI = 0.98) samples. Cross-validation in Tanzanian adults provided a reasonable fit (CFI = 0.98). Multiple-group CFA demonstrated acceptable fit [chi(2) = 140.829, degrees of freedom (d.f.) = 24, CFI = 0.98] for the unconstrained model, whereas unconstrained and constrained models were statistically significantly different. Factorial validity was confirmed for the three-factor OIDP model. The results provide evidence for cross-cultural equivalence of the OIDP, suggesting that this measure is comparable, at least to some extent, across Tanzanian and Ugandan adolescents.

The classification systems of the EQ-5D, the HUI II and the SF-6D: what do they have in common?

PURPOSE

EQ-5D, HUI II and SF-6D often produce very different valuations for the same health state. This paper aims at clarifying to what extent this might be caused by differences between the multi-attribute classification systems belonging to these instruments.

METHODS

Subjects were 264 patients of rehabilitation clinics in Mecklenburg-Western Pomerania (44.3% female; mean age 49.1) who completed the EQ-5D, the HUI II and the SF-36 (the basis of the SF-6D). After scaling with principal component analyses for categorical data, each attribute of each classification system was regressed on the classification systems of the other two instruments, and all attributes together were subjected to ordinary principal component analysis with varimax rotation.

RESULTS

Adjusted multiple R(2) for regression analyses ranged from 0.01 to 0.57. The HUI II attribute 'sensation' and the SF-6D attribute 'role limitation' are virtually unrelated to the remainder. All other attributes of all three instruments can be predicted by each other. EQ-5D and HUI II focus distinctly more on physical functioning than SF-6D.

CONCLUSION

Although all three classification systems have a lot in common, they differ so much that EQ-5D, HUI II and SF-6D would produce different valuations even if these valuations were determined according to the same principle.

Health-related quality of life and help seeking among American Indians with diabetes and hypertension

OBJECTIVE

To evaluate the Health-Related Quality of Life (HRQoL) of American Indians with diabetes, hypertension, or both conditions using the SF36; and to explore how the HRQoL is associated with help seeking among American Indians with and without these chronic conditions.

METHODS

We analyzed data obtained from respondents with diabetes and/or hypertension who participated in a large epidemiological study of two culturally distinct American Indian tribes. Comparison data were provided by an age, gender, and tribe matched sample from the same study who did not report either condition.

RESULTS

The respondents with both diabetes and hypertension had the lowest HRQoL on all eight subscales of SF36. Confirmatory factor analysis (CFA) showed that the assumption of equivalent factor loadings for participants with and without diabetes and/or hypertension was not satisfied. Biomedical service use was significantly associated with the SF36 physical health factor in those with hypertension only. Help seeking from traditional healers was significantly negatively related to physical factor scores for all the respondents except those with diabetes only.

CONCLUSIONS

Participants with comorbid diabetes and hypertension had worse HRQoL. The relationships between HRQoL and different types of help seeking varied depending on the comorbidity status of the respondents.

Oral health behavior among 25-year-old-Norwegian adults: factor structure, factorial invariance over time and trends

BACKGROUND

Exploratory factor-analytical studies suggest that health behaviors are multidimensional, leading to hypotheses that such behaviors are bi- or tri-dimensional. This study applies confirmatory factor analysis (CFA), to semi-longitudinal data and provides new information about the factor structure of oral health-related behaviors among 25-year-old Norwegians. The purposes of the study were to (1) evaluate the factor structure of oral health behaviors and its invariance over time, (2) assess temporal changes in patterns of oral health behaviors and in their socioeconomic distribution between 1997 and 2007.

METHODS

Simple random samples of 1190 residents born in 1972 and 8000 residents born in 1982 were drawn from the populations of three counties in Western Norway in 1997 and 2007. Structured questionnaires were mailed to the eligible participants. After one reminder, 735 (58% women, response rate 62%) and 1509 (63.3% women, response rate 19%) replied.

RESULTS

A correlated three-factor model with cross-loadings showed a better fit than a two-factor model to both the 1997 sample: chi(2)/df = 2.1, CFI = 0.95, RMSEA = 0.03 and the 2007 sample: chi2/df = 3.1, CFA = 0.95, RMSEA = 0.04. Multiple-group CFA showed an acceptable fit for the unconstrained model, CFA = 0.95, RMSEA = 0.03, and no statistically significant difference in fit between the unconstrained and constrained models (P = 0.739). Multiple binary logistic regression with three sum scores based on the behavioral factors sugar intake, drug use and oral health-enhancing behavior revealed that the odds ratios for frequent sugar intake (OR = 0.6, 95% CI: 0.5-0.8) and oral health-enhancing behavior (OR = 0.6, 95% CI: 0.5-0.7) were less in 2007 than in 1997. Drug use remained stable over time (OR = 0.9, 95% CI: 0.7-1.1). Educational differences in sugar intake observed in 1997 had leveled off in 2007.

CONCLUSION

A three-factor structure fitted the data in 1997 and 2007 and the factor structure was invariant over time. This suggests that oral health behaviors should be addressed jointly in oral health promotion programs.

A randomized trial of a CAM therapy for stress reduction in American Indian and Alaskan Native family caregivers

PURPOSE

Although it is widely recognized that caregivers of individuals with dementia experience elevated stress that places them at increased risk for health problems, little is known about how caregiving stress may be alleviated among underserved ethnic minority populations. The purpose of this study was to compare a complementary and alternative medicine therapy, polarity therapy (PT), to an enhanced respite control condition (ERC) to reduce stress and depression and improve quality of life for American Indian (AI) and Alaskan Native family caregivers.

DESIGN AND METHODS

Forty-two AI family caregivers of individuals with dementia, living on and off reservations in the Pacific Northwest, were randomized to an 8-session trial of PT or ERC. PT is a touch therapy that uses gentle pressure on energy points and biofields to help the client achieve physiological relaxation. ERC included respite care for the person with dementia and a choice of activities for the caregiver. Average age of caregivers was 50 years (range 27-69 years); 90% were women; 52% daughters, 10% wives, 7% sons, and 31% other relatives. Outcome assessments administered at baseline and posttreatment included caregiver perceived stress, depression, quality of life, sleep quality, worry, and physical health.

RESULTS

PT participants improved significantly more than ERC participants on stress (p = .01), depression (p = .045.), bodily pain (p = .02), vitality (p = .03), and general health (p = .01).

IMPLICATIONS

These results indicate that the delivery of PT to AI dementia family caregivers is feasible and culturally acceptable and may be an important approach to reducing stress, depression, and pain.

A randomized trial to increase physical activity among native elders

OBJECTIVE

Physical inactivity is common among older populations and American Indians. Our objective was to compare two methods for increasing physical activity and walking among American Indian elders.

METHODS

We conducted a two arm randomized trial to increase physical activity in 125 American Indians aged 50-74 years at the Seattle Indian Health Board in 2005. Participants were randomized into either an activity monitoring (N=63) or activity monitoring with a pedometer (N=62) arm over a six-week period. Outcomes included self-reported physical activity and well-being, and the 6-min walk test.

RESULTS

There were no group differences in self-reported physical activities and well-being. The 6-min walk test yielded no between-group differences. All participants increased the frequency of leisure walking (p<0.01), frequency of all exercise-related activities (p<0.01), frequency of moderate-intensity exercise activities (p<0.01), and improved weekly caloric expenditure for all exercise activities (p<0.05) by the end of the trial.

CONCLUSIONS

Pedometers did not confer enhanced performance on the physical activity outcomes beyond those achieved through self-monitoring. Physical activity can be promoted among at-risk groups in a brief, inexpensive manner in primary care. Exercise prescription and culturally relevant enhancement strategies may optimize physical activity outcomes for elder American Indians.

MOS-SF 36

The objective was to study the construct validity of the MOS SF-36 (Medical Outcome Study, short form questionnaire, version of 36 items) using structural equation modeling (SEM). Despite the widespread use of the questionnaire, several problems with the measurement model have been shown in the past, and it is highly disputable whether the computation of two component (summary) scales according to the published algorithm is a valid condensation. The SEM was conducted with the data of N = 2,874; the SF-36 was part of a questionnaire given prior to acupuncture treatment. The results indicated poor construct validity of the proposed structure of the first and second order factor solutions. First and foremost, contrary to the algorithm stated in the manual, the two component scales are not uncorrelated. Second, the overall fit of the original measurement model does not reflect the data structure very well. The current measurement model is discussed and starting points for revisions are provided.