There were 417 responses to the survey. Responses were screened for data quality including for potential duplicate responses and lack of engagement, with 18 responses removed for incomplete data or having a completion time less than half the median completion time. Responses were forced, so there were no missing data. After inspecting the included data (n = 399) for multivariate normality, five outliers were removed. The included sample (n = 394) were a mean age of 45.8 years old (SD 15.73). The majority of participants reported to not have any personal or professional end-of-life care experience (n = 243, 61.7%). A minority reported to have personal end-of-life care experience, considering themselves (n = 10, 2.5%) or a close person (n = 37, 9.4%) to be in the last few years of life, or reporting to have been bereaved in the last two years (n = 67, 17%). A minority reported to have professional end-of-life experience, either working or volunteering with people at end of life (n = 41, 10.4%) or individuals experiencing grief or bereavement (n = 27, 6.9%) or having attended training on helping people with dying, grief or bereavement (n = 29, 7.4%). Table 1 shows the other medical and socio-demographic information for this sample.

Table 1 Medical and socio-demographic characteristics of sample (n = 394)Dimensionality

ML estimation method with bootstrapping was used to provide a more accurate estimation of standard errors in relation to p values and confidence intervals. The Bollen-Stine bootstrap p was used as an alternative to χ2 [39]. The bootstrapping sample was 250, with 95% confidence interval as recommended by Nevitt and Hancock [40].

The first model specified was the 29 items loading on to their 8 respective factors as per the original model reported in the initial development of the DLI [13]. This refers to 4 subscales, two of which have their own 2 subscales; 1. Practical Knowledge including the (i) ‘Talking Support’ subscale and (ii) ‘Doing hands on care’ subscale, 2. Experiential Knowledge, 3. Factual Knowledge and 4. Community Knowledge including (i) ‘Accessing Help’ subscale and (ii) ‘Support Groups’ subscale. This model was a good fit of the data; χ2 (369) = 822.12, p < 0.001, Bollen-Stine bootstrap p = 0.004, Q = 2.23, CFI = 0.94, RMSEA = 0.07 (90% CI, 0.050-0.061), SRMR = 0.07. There were no items with low factor loadings (< 0.40), and no modification indices suggesting significant cross-loadings (> 0.30). A second model was specified to test whether the inclusion of a new item in the Factual Knowledge subscale (‘I know the contribution the funeral home staff can make at end of life’) impacted model fit. This replaced an original item (‘I know about the contribution the cemetery staff can make at end of life’) as it was deemed more culturally appropriate for UK respondents. There was a slight reduction in terms of the model fit for this second model but this model was still a good fit on the majority of indices; χ2 (369) = 871.69, p < 0.001, Bollen-Stine bootstrap p = 0.004, Q = 2.36, CFI = 0.93, RMSEA = 0.07 (90% CI, 0.054-0.064), SRMR = 0.07. Nonetheless, the factor loading of the new item (Q24) was greater (0.71) than the original item (0.63), with the reliability and factor loading of the Factual Knowledge subscale on the death literacy latent variable remaining largely consistent. Modification indices, however, showed a degree of variance shared between the new item and another item on the same subscale (‘I know how to navigate funeral services and options’). In a third model, the new replacement item was retained (‘I know about the contribution the cemetery staff can make at end of life’) and its error term was co-varied with the item (‘I know how to navigate funeral services and options’). This resulted in overall model fit indices superior to the initial specified model; χ2 (368) = 812.83, p < 0.001, Bollen-Stine bootstrap p = 0.004, Q = 0.2.21, CFI = 0.94, RMSEA = 0.07 (90% CI, 0.050-0.061), SRMR = 0.07. The path diagram for this final model is presented in Fig. 1. The final 29 items of the DLI measure validated for UK context, their beta weights (β), that is their factor loadings, as well as, the proportion of variance in the latent construct explained by that item (r2) are reported in Table 2.

Fig. 1

Path diagram of DLI final model

Table 2 The Death Literacy Index, internal consistency, and descriptive statistics of 8 subscales, and psychometric properties of 29 final scale itemsInternal consistency

The Cronbach’s alpha for each subscale were between α = 0.76 and α = 0.93, with the Omega coefficient between ω = 0.78 and ω = 0.93 (see Table 2), evidencing good internal consistency without homogeneity. All item to total correlations met the minimum criteria of r > 0.30.

Construct validityConvergent validity

Convergent validity can be evidenced with significant moderate positive associations between the subscales/DLI total score and objective knowledge of the death system, between the DLI and death competence (Coping with Death Scale; [14]), and between the DLI and actions relating to death and dying in the family and community (see Table 3) as hypothesised. Overall, more than 75% of the results are consistent with the predefined hypotheses in terms of direction of the effect (H1, H2 & H3). However, the strength of the correlation was not as expected and was weak for the subscales/DLI total score for the majority of constructs, apart from death competency where moderate correlations as hypothesised were observed.

Table 3 Convergent validity and discriminant validity of the Death Literacy Index (r)Known groups validity

Known groups validity was assessed for individuals identifying as having professional expertise in end-of-life care or bereavement, professional training, or lived experience. Due to a low number of participants identifying as being in the last years of life (n = 10), this subgroup was not assessed. Table 4 shows that all roles, apart from being a carer of someone who is at the end of life, are related to higher mean scores on all the DLI subscales in comparison to individuals identifying with none of the ‘expert’ roles in line with hypothesised findings (H4). The eta-square statistics show that the strength of these relationships was either medium to large on the subscales, and large for the DLI total score. Individuals identifying as a carer of someone at the end of life report significantly higher levels of death literacy on the majority of subscales and the DLI total score, however all effect sizes were small.

Table 4 Known-groups validity of the death literacy indexDiscriminant validity

There was a significant negative association between the majority of the DLI subscales/DLI total score and loneliness (Short Revised UCLA Loneliness Scale; [18]) (see Table 3) in line with what was predicted (H5). However, the eta-square statistics show the strength of these relationships were weak overall and not the moderate associations expected.

Interpretability

Interpretability was assessed using the individual raw data for each subscale, i.e. the item totals of participants’ scores. The participant’s total score on each subscale represented the total possible range for all subscales (see Table 5). There was no evidence of floor or ceiling effects on DLI total score, or the majority of subscales except for ‘Factual Knowledge’. Using the criterion of > 15% of respondents achieving the lowest possible score, there is some evidence of a floor effect for this subscale.

Table 5 Median, range, interquartile range and floor and ceiling effects of the Death Literacy IndexUK population DLI benchmarks

The scaled mean scores for each of the subscales and the DLI total score is reported for the UK population (see Table 6). Individuals from the UK appear to have high levels of experiential knowledge and the ability to talk about death and dying, relative to other subscales.

Table 6 Scaled mean scores for the UK on DLI and its subscalesRelationship between DLI and demographic variables

In relation to demographic variability in the DLI, the majority of demographic variables were either non-significant or reported weak effect sizes (see Table 7), demonstrating little variability in DLI to be explained by demographics. The following demographic variables were not significantly associated with the DLI at the 0.05 significance level; gender, highest level of education, employment status, annual household income, relationship status, caring for dependent adults, having a chronic mental illness, and belief in an afterlife. Due to small subgroup size, associations could not be explored for individuals with terminal illness.

Table 7 Summary of significant relationships between demographic variables and the death literacy index

The eta-square statistic for age reports a moderate effect size. Post hoc analysis using the Games-Howell criterion for significance indicated a positive relationship with age, with the DLI mean score higher for > 58 year olds (M = 3.11, SD = 0.77) than in 38–47 year olds (M = 2.76, SD = 0.69) or 28–37 year olds (M = 2.61, SD = 0.52), and the DLI mean score higher in 48–57 year olds than 28–37 year olds. The relationship with age was however not linear, with 28–37 year olds reporting a lower DLI mean score than 18–27 year olds (M = 2.90, SD = 0.61).