The world is experiencing demographic revolution, with the number of the elderly population increasing dramatically(1). China has also marched to an ageing society; at the end of 2006, there were about 104·2 million people over 65 years of age, which accounted for 7·9 % of the total population(2). Ageing is accompanied by physiological, psychological, social as well as economic changes, which determine that the elderly population may become vulnerable to inadequate nutrition(Reference Chen, Schilling and Lyder3, Reference Brownie4). The terms ‘malnutrition’ and ‘undernutrition’ tend to be used interchangeably in the literature. Within the present paper, the term malnutrition refers primarily to undernutrition.
Malnutrition is especially harmful for older adults. Not only does it contribute to many non-specific symptoms commonly observed in older adults, such as chronic fatigue, a feeling of ill health and poor appetite(Reference Manandhar5), but also it is a major risk factor for illness, hospitalization, poorer recovery, poorer quality of life, longer stay in hospital(Reference Visvanathan, Macintosh, Callary, Penhall, Horoitz and Chapman6), increased cost of health resources, more complications, increased morbidity and mortality(Reference Chen, Schilling and Lyder3).
However, nowadays malnutrition is frequently unrecognized and untreated(Reference Kelly, Tessier, Cahil, Morris, Crumley and McLaughlin7). Because of different settings, methods and operational indicators, different prevalences of malnutrition and risk of malnutrition have been reported. As assessed by the Mini Nutritional Assessment (MNA), the prevalence of malnutrition in community older adults (n 14 149) was 0–8 % and the risk of malnutrition was 8–76 %(Reference Guigoz8). Furthermore, in the UK, McWhirter and Pennington(Reference McWhirter and Pennington9) reported that 40 % of patients admitted to hospital from the community were malnourished and most were discharged with worse nutritional status than when they entered, establishing a vicious circle and adding a further group of malnourished individuals to the community. Older adults in the Chinese community still have poor nutrition knowledge and attitude as well as behaviour(Reference Zeng, Huang, Ying, Chen, Luo and Shuai10); doctors and nurses also lack awareness of the prognostic significance of undernutrition and knowledge regarding nutrition assessment and management(Reference Nightingale and Reeves11).
Functional capacity is recognized as the sixth vital sign and the most universally accepted indicator of health status in older adults(Reference Bierman12). Functional independence determines the ability of elders to be productive, which was also identified by them as their main criterion of well-being and quality of life(Reference Hellstrom and Hallberg13). In China, it is especially important for older adults to preserve functional ability, as they often make significant contributions to family welfare and income via their involvement in tasks such as child care and food preparation, thus freeing younger adults for wage earning. The level of functional ability has a considerable impact on the way elders are treated and respected(Reference Kikafunda and Lukwago14).
Over the past decades, researchers have reported some sociodemographic factors to have direct or indirect impact on elder nutrition(Reference Chen, Schilling and Lyder3–Reference Manandhar5, Reference Kikafunda and Lukwago14–Reference Callen and Wells21). Dependency in activities of daily living was frequently reported to influence the nutrition of geriatric patients or frailer elderly(Reference Castel, Shahar and Harman-Boehm22); functional decline also impacted the nutrition of free-living elders although the Instrumental Activities of Daily Living Scale (IADL) was not used as a systematic criterion(Reference Wylie, Copeman and Kirk18, Reference Wikby and Fagerskiold19, Reference Callen and Wells21).
Older adults in the community should be assessed for risk of malnutrition before severe changes in weight and blood biochemistry occur(Reference Guigoz8). However, in China where primary health service care has just started, only BMI tends to be used to identify underweight(Reference Stookey, Zhai, Zohoori and Popkin20) and the risk of malnutrition among community older adults is largely unavailable. A Chinese study(Reference Fei, Cheng, Shi and Cao23) investigated the risk of malnutrition among retired Shanghai residents, but did not identify its risk factors. Evidence of functional effect on the nutrition of Chinese community older adults also has not been established.
We are frequently called upon to support people within the community rather than in institutional facilities. Awareness of the possibility of malnutrition in community older adults is important, especially as those at risk of malnutrition – if identified – respond well to intervention, which may reverse its course. Effective manipulation of any problem necessitates identification and analysis of risk factors. Therefore, the aims of the present study were to: (i) examine the levels of nutritional and functional status; (ii) identify the relationships between nutrition and other variables (demographic characteristics, functional status); and (3) explore the predictors contributing to poor nutrition for older adults.
Methodology
Design, setting and subjects
A cross-sectional, descriptive correlation design was utilized. A convenience sample of 162 older adults was recruited from a community of a city in central China. There are about 26 489 resident households and 75 315 permanent residents in the local community. The residents could receive health-related services from large-scale hospitals or a local health service centre or nearby health service stations; of those nine stations, five were authorized for data collection. Selection criteria included older adults who were: (i) living in the community; (ii) 65 years old or over; (iii) able to stand for weight measurement; (iv) able to communicate with the investigator; and (v) had no cognitive impairment. Each eligible older adult was introduced to the investigator by the community health-care providers. Within the area every station serviced, data were gathered in the health station or activity centre or community hall; only a few were collected in the homes of participants who were receiving home care.
Data gathering lasted from July to September, 2007. Based on a power analysis using a moderate effect size (R 2 = 0·13), a power of 0·80 and a significance level of 0·05, a sample size of 110 participants was needed(Reference Polit and Beck24). One hundred and seventy-five older adults met the criteria, eight refused to participate and five dropped out during the process.
Measurements and instruments
A demographic data questionnaire asked the participants about age, gender, marital status, living status, education level, personal monthly income and chronic medical conditions suffered.
The MNA, created by Guigoz et al.(Reference Guigoz, Vellas and Garry25), was used to assess nutritional status for older adults. The eighteen items can be divided into four parts: (i) anthropometric measurement (BMI, mid upper-arm circumference (MUAC), calf circumference (CC), weight loss); (ii) global assessment; (iii) dietary assessment; and (iv) subjective assessment. It eliminates the need for more invasive tests to measure blood biochemical indices. The total score (maximum, 30) can be used to classify older adults as malnourished (<17), at risk of malnutrition (17–23·5) or nourished (>23·5). Reported internal consistency is 0·83, test–retest reliability is 0·89(Reference Bleda, Bolibar, Pares and Salva26). In the present study, the reliability α was 0·798. The investigator received permission from the copyright holder, Nestlé Nutrition, to use the MNA.
The IADL, developed by Morris et al.(Reference Morris, Carpenter, Berg and Jones27), was used to assess functional ability. It asks older adults about their performances concerning seven tasks: (i) meal preparation; (ii) ordinary housework; (iii) managing finances; (iv) managing medications; (v) telephone use; (vi) shopping; and (vii) transportation. The possible responses to the specific tasks are: ‘independent’ (=0), ‘some help’ (=1), ‘full help’ (=2) and ‘by others or activity did not occur’ (=3). Total score ranges from 0 to 21, 0 means completely independent and higher scores indicate more dependency. The average inter-assessor reliability was 0·77(Reference Morris, Fries, Steel, Ikegami, Bernabei and Carpenter28). The reliability α for the present study was 0·888. Permission to use the IADL was obtained from the copyright owner, interRAI Corporation.
The two instruments were originally written in English; they were first translated into Chinese, then back-translated into English and the back-translated version was checked against the original English version by a native English speaker prior to use in the study.
Anthropometric measurements consisted of height, weight, CC and MUAC. Measurements were taken by the investigator throughout to minimize intra-interviewer variation and strictly adhered to the anthropometric measurement manual. For the twelve older adults with severe spinal curvature, knee heights were measured and equations especially relating to Chinese older adults were utilized to estimate stature(Reference Li, Tang, Wong, Lui, Chan and Dai29):
BMI was calculated as weight (kg)/[height (m)]2; BMI classification for adults of the Asia-Pacific Region was used(30).
Procedure and ethical considerations
Permission for data collection was obtained from the administrators of the community and the five health stations. Each potential participant was informed that their involvement was completely voluntary. Once oral informed consent was obtained, the questionnaires were administered. History and information were obtained from participants as well as health providers, supplemented by reviewing health files. Considering the potential existence of illiteracy, weak eyes and inadequate understanding, the researcher only read out the specific items without giving further explanation to avoid introducing bias. Anonymity and confidentiality were respected.
Data analysis
Descriptive statistics were used to address the levels of nutritional and functional status. To analyse the relationships, Spearman’s correlation was utilized since some variables were nominal. Stepwise multiple regression analysis was conducted to identify the best predictors. All data were entered into the SPSS statistical software package version 15·0 (SPSS Inc., Chicago, IL, USA) for analysis and a value of P < 0·05 was considered significant.
Results
Demographic characteristics
The characteristics of the 162 elders are outlined in Table 1. Twenty-eight (17·3 %) had no income and relied totally on adult children or a spouse as their financial source; forty-six (28·4 %) obtained a pension that was lower than the mean pension (812 RMB) in Wuhan centre urban community.
Chronic medical conditions
The number of chronic medical conditions and prevalence of common conditions are presented in Table 2. Only seventeen (10·5 %) participants were free of chronic medical conditions, others suffered one to seven unequally. The most frequent chronic medical conditions were hypertension (51·2 %), bone and joint disease (43·8 %) and digestive system disease (gastritis, peptic ulcer, partial gastrectomy, gallbladder disease, pancreatic insufficiency, chronic hepatitis; 35·1 %).
Classification
The mean MNA score was 23·8 (sd 3·92), 36·4 % (n 59) were at risk of malnutrition, 8·0 % (n 13) were malnourished, the remaining 55·6 % (n 90) were nourished; and 61·7 % (n 100) were functionally independent. The frequencies of points for the individual MNA questions revealed that protein products intake was reduced for 73·5 % (n 119) of elders, while 96·3 % (n 156) took fruits or vegetables with adequate daily amounts; during the past three months, 31·5 % (n 51) suffered stress or acute disease, and food intake declined due to severe (5·6 %, n 9) or moderate (27·2 %, n 44) loss of appetite; 14·8 % (n 24) took more than three prescription drugs daily; 17·3 % (n 28) regarded themselves as malnourished and 35·2 % (n 57) were unable to estimate their nutritional status; 24·7 % (n 40) perceived their health status were poorer than others and 17·3 % (n 28) were unable to give such an estimation.
Tables 3 and 4 summarize nutritional and functional status classification according to BMI and IADL.
Correlations
Table 5 displays the correlations between nutritional status and the independent variables (demographic characteristics, functional status). Age, marital status, education level, personal income, number of chronic conditions and IADL function had significant correlations with MNA score.
MNA, Mini Nutritional Assessment; IADL, Instrumental Activities of Daily Living Scale.
Predictors
Table 6 shows the combination of demographic characteristics and functional status predicting nutritional status according to the MNA. Number of chronic conditions suffered, age, functional status and marital status all entered the regression equation.
MNA, Mini Nutritional Assessment; IADL, Instrumental Activities of Daily Living Scale.
Discussion
Functional status
The current study found that 38·3 % of older adults needed help to deal with at least one activity of daily living, which is similar to the prevalence found in a previous study(Reference Tang, Wang, Zhao, Feng, Chen and Zhang31). The order of items in increasing difficulty of performance was: managing medications, telephone use, managing finances, meal preparation, transportation, ordinary housework and shopping. This was a little different from Tang et al.(Reference Tang, Wang, Zhao, Feng, Chen and Zhang31), who surveyed the IADL function of urban community elders from Anhui province, China, where handling finances resided in the position of the second most difficult with the others being similar. Perhaps this is because the present study excluded those with cognitive problems while the Anhui study did not have such a selection criterion. Cromwell et al.(Reference Cromwell, Eagar and Poulos32) illustrated that handling finances needed more cognitive components and memory, and was even called cognitive IADL.
Participants rated shopping as the most difficult task, which might be due to its complex and multiple procedures. First, elders have to access big supermarkets, some have to pass along uneven pavements and crossings; then in the supermarket, elders could encounter many problems, such as searching, bending or stretching for items; finally, carrying shopping is not so easy for them. Managing medication can be dealt with and encountered the least difficulty; this might be because most older adults have taken medication for decades.
Nutritional status
In the present study, the percentage of malnutrition (8·0 %) and suspected malnutrition (36·4 %) was within the range reported for community-dwelling elders(Reference Guigoz8). Only one Chinese study, conducted in Shanghai(Reference Fei, Cheng, Shi and Cao23), can be used for direct comparison; the corresponding percentage was 1·7 % and 19·1 %, respectively. There are four possible explanations for the striking difference. The first relates to geographical inequalities; there are significant differences in several aspects between Wuhan and Shanghai, and the former is in poorer position. Elia and Stratton(Reference Elia and Stratton15) have stated there is geographical inequality in nutrient status among older adults. Second, 17·3 % of elders of the present study were financially dependent, while all participants in the Shanghai study were retired residents. Kabir et al.(Reference Kabir, Ferdous, Cederholm, Khanam, Streatfied and Wahlin16) have reported that income has a positive correlation with protein and energy intake. Third is the age disparity; age range was 50–89 years (mean 67·5 (sd 9·0) years) for the Shanghai study participants and 65–94 years (mean 74·14 (sd 5·95) years) for the current study. Elia and Stratton(Reference Elia and Stratton15) also demonstrated that older elders were prone to suffer from poor nutrition. Fourth, Wuhan is one of the three ‘stove’ cities in China; the data were collected in the hottest season, and some elders said they had lost their appetite and weight just because of the unbearably hot summer weather.
BMI data revealed that underweight and obesity coexisted in the community, which is in accordance with previous results(Reference Stookey, Zhai, Zohoori and Popkin20, Reference Fei, Cheng, Shi and Cao23). When compared with the national study(Reference Stookey, Zhai, Zohoori and Popkin20), which surveyed the BMI of Chinese elders aged 60 years or over, the underweight rate (14·8 % in present study v. >15 % nationally) and obesity rate (25·3 % v. 24 %) are comparable. Perhaps the economic development of China has stimulated the alteration of food consumption, which buffers or exceeds the influence of age.
The frequency of points for specific MNA items revealed that inadequate intake of protein products was a serious problem and dairy products were not habitually consumed. Some elders were too restrictive in their choice of diet: for instance, because of a cholesterol-restrictive order, they dared not eat eggs at all; most elders with diabetes mellitus said they never felt full but dared not eat. Just as Zeng et al.(Reference Zeng, Huang, Ying, Chen, Luo and Shuai10) reported, we also observed that some elders did not acknowledge the significance of diet and a varied understanding of the components of a healthy diet existed. In some developed Western countries, older adults also strived to achieve a healthy diet(Reference Kearney, Gibney, Livingstone, Robson, Kiely and Harrington33); nevertheless, for Chinese elders with relatively less knowledge, alternative diets and concrete guidelines must be available.
Because many elders (31·5 %) suffered stress or acute disease and so many (14·8 %) took more than three prescription drugs daily, community health professionals should be alert to their psychological well-being and ensure optimal prescribing. Worse, some perceived themselves as malnourished or thought their health status was poorer than others; while some others could not give any such estimation. None the less, Griep et al.(Reference Griep, Mets, Collys, Ponjaert-Kristoffersen and Massart34) demonstrated that self-rated health had a predictive value for MNA score, so appropriate guidelines on nutrition must be provided for the elderly.
Correlations
Education level was positively associated with MNA score, which is comparable with previous findings(Reference Kabir, Ferdous, Cederholm, Khanam, Streatfied and Wahlin16). In China, Zeng et al.(Reference Zeng, Huang, Ying, Chen, Luo and Shuai10) indicated that education was the major factor influencing community elders’ nutrition knowledge, attitude and behaviour. A Ugandan study(Reference Kikafunda and Lukwago14) reported that exposure to nutritional knowledge was a predictor of BMI for older adults. Well-educated elders were knowledgeable about disease and elderly-specific daily diet regulations, which played an important role for their nutritional health.
Personal income was found to be positively related with MNA score, which is in accordance with other literature(Reference Chen, Schilling and Lyder3, Reference Kabir, Ferdous, Cederholm, Khanam, Streatfied and Wahlin16). Chen et al.(Reference Chen, Schilling and Lyder3) reported that low income was related to decreased variety and quantity of food consumed, and financial dilemma could limit purchasing, meal preparation and storage facilities. Low income also influenced consumption of some healthier alternatives which carry a price premium. In China, the disparity between the rich and the poor is increasingly deteriorating(Reference Li35), so China also presents some conditions that are unobservable in the developed nations. In fact, the pension has increased several times and is enough for daily expenditure. Since many young people are laid-off workers with so much economic stress to raise their children, so the pension always contributed substantially to household budgets. Consequently, in those elders experiencing difficult economic circumstances, where food is not deemed a priority, disease may take precedence.
Age had a significant negative correlation with MNA score, which is similar to a prior study(Reference Elia and Stratton15). Brownie(Reference Brownie4) demonstrated that ageing was associated with distinct changes in body composition and gastrointestinal function, which might reduce motility rates and disrupt digestion or absorption. Chen et al.(Reference Chen, Schilling and Lyder3) and Brownie(Reference Brownie4) also reported the that ability to observe, smell and taste food decreased with ageing. Reduced sensitivity but elevated taste threshold for all taste modalities occurs frequently, with sweet and salty tastes declining first; thus elders can only taste sour or bitter flavour, which may affect their desire for food. Chapman et al.(Reference Chapman, MacIntosh, Morley and Horowitz36) showed that ageing was associated with increased satiety factors and a reduced feeding drive.
The widowed were predisposed to suffer from poor nutrition, which is comparable with previous reports(Reference Chen, Schilling and Lyder3, Reference Wylie, Copeman and Kirk18, Reference Hansson, Jones, Carpenter and Remondet37). Spouses act as a social support and provide the long-term partnership associated with food, including meal preparation and companionship at meal times(Reference Wylie, Copeman and Kirk18). Hansson et al.(Reference Hansson, Jones, Carpenter and Remondet37) reported the widowed might have difficulty in forming new attachments, in coping and caring about life, and might tend to suffer the consequences of depression and malnutrition. Wylie et al.(Reference Wylie, Copeman and Kirk18) also showed that the elderly changed their food intake or ate less as a result of the death of their spouses. For a recently widowed elder who has not been responsible for shopping and cooking, the situation could be worse.
As suggested in prior literature(Reference Brownie4, Reference Wikby and Fagerskiold19, Reference Callen and Wells21), the number of chronic medical conditions that each elder suffered had a significant negative correlation with MNA score. There are two main relevant reasons(Reference Schenker38). First, disease is accompanied with tissue repair and an increased activity of body defence mechanisms, which means increased nutrition requirements; notwithstanding, illness is often associated with a decreased desire for food. Second, elders suffering multiple chronic conditions tend to take various medications, which probably contribute to adverse drug reactions and drug-induced malnutrition. Hanlon et al.(Reference Hanlon, Schmader, Rudy and Weinberger39) stated that community-dwelling older Americans took an average of 2·7–4·2 prescriptions and over-the-counter medications. Griep et al.(Reference Griep, Mets, Collys, Ponjaert-Kristoffersen and Massart34) even reported that the number of medications that elderly take was the best predictor of MNA score. The mechanisms include hindering of appetite, nutrient absorption, metabolism and excretion.
The current study suggested there was no significant correlation between living status and MNA score. In contrast, Visvanathan et al.(Reference Visvanathan, Macintosh, Callary, Penhall, Horoitz and Chapman6) reported living status was an independent predictor of MNA score. Perhaps this arises because most studies analysed the impact of living alone on elder nutrition, whereas the present study explored the relationship between nutrition and whether they were living with children or not. Those having a house and living separately could prepare meals according to their preference and taste, and the meal time is more flexible.
Functional dependency influences elder nutrition through limiting diet availability and accessibility. Callen and Wells(Reference Callen and Wells21) determined that those community elders with higher functional ability had more help to maintain nutritional health, and difficulty with transportation was a significant barrier while the ability to shop was an important aid in maintaining good nutrition. McCormack(Reference McCormack40) and Wylie et al.(Reference Wylie, Copeman and Kirk18) reported that incapability of transportation could impinge on social interaction and impede participation in socialization of eating patterns, which could result in deterioration of social networks and indirectly impact on nutrient intake. In the current study, some also complained they could not pursue their interests and pleasures because of transportation limitation. What is worse, according to Chinese tradition, elderly parents should live with the son and daughter-in-law and was supported, whereas daughters are concerned about parents more. If their daughters are living in the same city, independent elders can go to their daughters’ frequently and enjoy favourite food that is specially prepared. Reliance on others to shop will result in less availability to fresh food(Reference Wylie, Copeman and Kirk18), especially among Chinese elders who are always are shy to ask somebody buy what they want to eat, only drop the idea. In Wuhan city, supermarket chains do not offer a free delivery service, which in Western countries functionally limited elderly could enjoy. Some specific diseases may compromise the ability of elderly persons to prepare meals, which also impacted the meal size they took(Reference Wylie, Copeman and Kirk18); moreover, especially nowadays that children are the priority, elders’ preference and taste were often overlooked, the food was seldom prepared in line with their expectation and their willingness to eat diminished. Schenker(Reference Schenker38) even described that budgeting skills could influence the nutrition of community older adults.
Functional independence also has impacts on elders’ personal values, interpersonal relationships and emotions, which might indirectly influence nutrition under the special Chinese culture. Wikby and Fagerskiold(Reference Wikby and Fagerskiold19) narrated that independence was a personal value and self-esteem for older adults an important factor stimulating their willingness to eat. Kikafunda and Lukwago(Reference Kikafunda and Lukwago14) stated that elder functional dependency influenced the way they were treated and respected, thus perhaps deteriorating the family relationship. In Chinese culture, it is especially apparent that the harmonious interpersonal relationship which is most difficult to establish is the one between mother-in-law and daughter-in-law, and conflicts always exist. Elder dependency means less contribution and more burden to the family, which is prone to exacerbate conflicts; the daughter-in-law would blame the elder doing nothing, just sitting and eating, argue with them and even be impolite to them, which was the most important and frequent source of elder negative mood in China. On the other hand, Wikby and Fagerskiold(Reference Wikby and Fagerskiold19) reported that rapport relationship with relatives brought elder positive mood, which made them feel satisfied, loved and relaxed, thus they enjoyed food and eating.
Jette et al.(Reference Jette, Feldman and Douglass41) found that community elders with physical disability had worse oral health relative to those with better functional ability, in that it affected elders’ ability to maintain oral hygiene and limited their accessibility to dental check-up and treatment. Visvanathan and Ahmad(Reference Visvanathan and Ahmad42) proposed that oral health problems could result in dietary intake reduction and alteration of food choices.
Predictors
The number of chronic medical conditions suffered, age, functional status and marital status were found to be the best predictors of elders’ nutritional status. That number of chronic conditions could predict nutrition is comparable with previous studies(Reference Visvanathan, Macintosh, Callary, Penhall, Horoitz and Chapman6, Reference Callen and Wells21). That age predicts nutrition is similar to prior literature(Reference Keller43), which demonstrated that increasing age was a predictor of undernutrition for long-term elderly in care. Functional dependency as a predictor is consistent with a prior study(Reference Wojszel44) reporting functional dependency on the IADL to be a predictor of low MNA score. That marital status predicts nutrition is in accordance with another study(Reference Kwon, Suzuki, Kumagai, Shinkai and Yukowa45) indicating that loss of spouse was a significant predictor of dietary variety decline for community older adults.
Limitations and future research
Several limitations of the present study require acknowledgement. First, the study was conducted only in a single community with relatively small sample size and a non-random sampling was used, which limits the generalization of the results. Second, the cross-sectional nature of the data does not allow examination of causal relationships. Third, the instruments were originally developed in a Western culture, which means that they may not be culturally sensitive to China. Future research is needed to improve data collection through random sampling, utilizing a larger and more diverse sample throughout China, developing locally relevant tools, and using a longitudinal design to infer causal relationships. Continued research is also needed to develop appropriate and concrete nutrition education and intervention programmes.
Conclusions and implications
In conclusion, the current study contributes additional knowledge about the nutritional and functional status of community older adults in China. It showed that a large proportion was at risk of malnutrition, although confirmed malnutrition was not apparent, and some elders could not live independently in the community. Not only did some demographic characteristics appear to be related with nutrition, functional status also was correlated with nutrition among elders. The best predictors were the number of chronic conditions suffered, age, functional status and marital status.
The findings present a challenge and call for the attention of primary health-care professionals, as well as relevant and significant others, to care for nutritional problems in elders. The findings may lead to targeted, cost-effective intervention according to the best predictors for the rapidly growing ageing population in China.
Acknowledgements
Sources of funding: The study was funded by the Research Grant from the HOPE School of Nursing, Wuhan University, China.
Conflict of interest declaration: None declared.
Authorship contributions: study design – Y.-H.H. and S.-J.L.; data collection – Y.-H.H. and Y.-L.Z.; data analyses – Y.-H.H.; manuscript preparation – Y.-H.H. and S.-J.L.
Acknowledgements: We thank all staff of the five health service stations and all participants for their contributions to our study.