Psychometric testing of the Determinants of Salt-Restriction Behaviour Questionnaire in people of Chinese ancestry: a methodological study

High dietary salt consumption is a global health issue and the cause of many non-communicable diseases including hypertension and renal disease [1, 2]. Dietary salt restriction is an effective primary and secondary preventive measure for hypertension [3‐5]. Currently, the World Health Organization (WHO) recommends a maximum daily salt consumption for healthy adults of 5 g (g) per day [1]. However, many adults consume higher than the recommended amount in their daily diets [6, 7]. This may be associated with cultural practices and personal food taste preferences.

A sociology study in 2011 estimated that more than 40 million individuals of Chinee descent lived in 148 countries around the world [8]. The 2016 Census found that over 5.1% (1.2 million) of Australians reported Chinese ancestry, and of these, only 25% were born in Australia [9]. An Australian study showed that Chinese immigrants who had resided in Australia for a longer period had more cardiovascular risk factors such as hypertension, diabetes and high cholesterol [10]. For example, the prevalence of hypertension among Chinese female immigrants who had lived in Australia for 30 years or longer was greater compared with those who had lived in Australia for less than 10 years (prevalence ratio = 1.47; p < 0.05) [10].

Recent statistics showed that average salt consumption in China was above 10 g/day [11], in Singapore it was 8.5 g/day [12], in Italy it was 9.0 g/day [13] and in Australia it was 9.6 g/day [14]. It is important to note that most salt consumption studies have focused on the main ethnic groups of the countries in which the studies were conducted. The dietary salt practices and related public health issues in minority population groups such as migrants are less explored. Further, the effects of Westernisation on food selections may influence non-Westerners’ dietary selections, leading to an increase in overall salt consumption. In general, dietary practices are often affected by multiple factors including personal preferences and cultural inheritance. Therefore, it is important to study the salt-related knowledge and perceptions of and perceived barriers to following a low-salt diet of the target Chinese population group.

Evidence showed that there was a close relationship between salt consumption and blood pressure [15]. With an increase of 2.5 g (1 g of sodium) in daily salt consumption increased the blood pressure by 2.11/0.78 mmHg and this effect was more significant in people who consumed more than 7.5 g of salt per day [15]. A recent literature review in 2022 suggested that salt-related health education might have positive influences on dietary behavioural changes and Chinese diasporas especially the new migrants might experience linguistic and cultural barriers when they seek dietary advice in their host countries [16]. Little is known about the current landscape and effects of the existing salt-related education and the challenges of reducing salt consumption for preventing hypertension among Chinese diasporas. Given more than 1.2 million (5.1%) Australians reported Chinese ancestry and that salt reduction is an effective preventive strategy for hypertension, there is a pressing need to assess the level of daily salt consumption, perceptions and knowledge in this ethnic group, and whether they continue the dietary practices learnt in their homeland or partially Westernise their meal patterns. The purpose of this study was to translate the original Determinants of Salt-Restriction Behaviour Questionnaire (DSRBQ) from Chinese to English and adapt it to the Chinese Australian context. The original DSRBQ was used in a series of salt restriction behavioural studies in Beijing, China (n = 403 [17], n = 513 [18] and n = 799 [19]). Overall, it has good reliability (Cronbach alpha = 0.757) and validity (accumulative contribution rate = 63.5%). However, it has not yet been adapted and translated into other languages. So, a validated tool is available to investigate the Chinese Australians’ salt-related behaviour and barriers to modify their salt consumption. The findings will inform the healthcare providers in the design of further salt reduction strategies for this population group.

Findings from this study show that both the revised Chinese and translated English versions of the DSRBQ [19] are valid and reliable tools for use with individuals of Chinese ancestry in Australia. The rigorous translation and psychometric-properties-testing ensured the cultural equivalence of the questionnaires. In phase 1 – the Translation equivalence and content relevance study, a total of six items were scored below the acceptable I-CVI level (0.80). As a result, the items were either revised or removed from the questionnaire including the items related to the salt reduction program in Beijing, China. The S-CVI was 0.95 after eight items were removed from the questionnaire, which indicated the DSRBQ had excellent content validity overall [33].

In general, a scale with a Cronbach’s alpha in the range of 0.65 to 0.80 is considered as having an acceptable level of internal consistency [31], but some studies accept lower alpha values of 0.45 and above [34]. Therefore, in the present study, both versions have acceptable levels of internal consistency (0.638 and 0.584 for the English and Chinese versions respectively for the items in Part 2) and test–retest reliability (0.820 and 0.688 for the English and Chinese versions respectively for the items in Part 3). In consonance with the theoretical framework of HBM, all key subscales demonstrated strong correlations and test–retest reliability over time.

In comparison with the previous validation study [18], our study successfully recruited a unique group of participants, who were young (mean = 35, SD12.9) and single (59.6%, n = 87) and had no hypertension-related medical conditions (n = 121, 82.3%). Of this group, 18.5% (n = 27) of the participants were born outside the Greater China region, such as the United Kingdom or Malaysia. The average age of the participants in our study was more than 20 years younger than participants in the previous study in China. As Chen & Liao [18] recommended, preventive options could be offered to those who are relatively young but at risk of hypertension due to high dietary salt consumption. So, the participants in our study are highly likely to benefit from measures for the primary prevention of hypertension. This validation study showed that both the Chinese and English questionnaires have acceptable psychometric properties, indicating that the questionnaires are suitable and appropriate for this ethnic group, and the findings can inform nurses of the specific dietary-salt-related health behaviour risks and barriers for individuals of Chinese ancestry when they modify their dietary practices.

The validated questionnaire has general demographic items followed by items about self-awareness of hypertension and health behaviour associated with dietary salt intake. The item-to-total correlation was used to measure the correlations between an item and the total score [35]. The acceptance range of the correlation value is from 0.3 to 0.7 [35]. The item-to-total correlation showed that items 1 to 3 in Part 2, which are related to knowledge of the daily maximum salt consumption, long-term health effects of salt and diagnostic criteria for hypertension, were below 0.3 in both versions. Although there was a marked improvement in the Cronbach’s alpha results when these three items were deleted, these items should be accepted and considered as very sensitive indicators for testing salt-related knowledge. This is because most participants could not correctly answer the essential knowledge items, and some of the responses were ‘I don’t know’. According to a previous psychometric testing study [36], people from different areas may have different levels of salt-related knowledge. Our participants were from very diverse backgrounds, which also reflected on the composition of the Chinese Australian population group. From a content point of view, if people do not know the recommended daily salt intake amount, hypertension diagnostic criteria and impact of salt on human health, they would not perceive excessive salt intake to be a health threat or take action to minimise the risks of hypertension. They are more likely to continue their current dietary salt habits, and adherence to maintaining a low-salt diet is likely to be suboptimal. Therefore, items 1 to 3 in Part 2 should remain in the questionnaire.

Cronbach coefficient alpha and ICC were used to assess the internal consistency and test–retest reliability for the Likert items (Part 3). All six subscales in both versions exceeded the recommended Cronbach alpha value of 0.70 at T1 [35, 37]. At T2, two subscales (perceived the benefits of using a measuring spoon in the English version and perceived barriers in the Chinese version) had Cronbach alpha values of 0.660 and 0.657 respectively. Although these values were below the recommended 0.70, the values were still above the acceptable level of 0.65 [31]. These results indicate strong overall internal consistency of the full scale. The ICCs for each subscale in Part 3 exceeded the suggested value of 0.40 [38]. Therefore, all Likert items/subscales were deemed to have sufficient test–retest reliability.

Construct validity was not conducted in this study. This was because no similar instruments could be used to compare with the findings from DSRBQ. The original DSRBQ has been rigorously validated and extensively used in China. It has good reliability (Cronbach alpha = 0.757) and validity (accumulative contribution rate = 63.5%). Gunawan & Marzilli [26] reported that construct validity may not be necessary if the translation process was accurate. In this study, the back-translation method and a translation equivalence evaluation completed by expert panel members were used to ensure the translation accuracy. So, the authors believed that the adapted DSRBQs had adequate construct validity.

In summary, the findings from this study indicate that both the Chinese and English versions of the DSRBQ [18] have sufficient validity and reliability to measure the dietary salt-related knowledge and health behaviours of people of Chinese descent. This questionnaire has the potential to identify the educational needs of clients as well as the roles of nurses in promoting and educating, using salt restriction as a method for primary and secondary prevention of hypertension for people of Chinese descent who are living in the Western world. Some health behavioural items (items 11 to 15 in Part 1) and knowledge items (items 4 to 6 in Part 2) have the potential to be removed to make the questionnaire more concise and able to be completed in a shorter period. This notion warrants further investigation into the content of the relevance of these items and their contribution to the overall questionnaire.

The validated DSRBQ can be used in people from a Chinese cultural background living in Australia. Further testing of the questionnaire could be performed with a different cohort as the questionnaire may be adapted for use with other Chinese or Asian diaspora groups. The validated DSRBQ will assist nurses to collect relevant data to develop a culturally based nursing assessment tool and interventions for individuals of Chinese descent who reside in a country where Chinese cultural practices are employed by a minority.

The DSRBQ has been revised and translated into English. The psychometric testing results indicate that both the English and Chinese versions have acceptable validity and reliability. The tools can be used in people from a Chinese cultural background living in Australia. With further testing, the tools may have potential for use with other Chinese or Asian diaspora groups. The findings from the tools will provide evidence about the health risks and education needs associated with dietary salt consumption in this population group. Such evidence will assist stakeholders to develop cultural appropriate community-based interventions to reduce salt intake for Chinese diaspora groups.