Study design, settings and sample
The 10/66 DRG has carried out a series of repeated cross-sectional surveys in Cuba, Dominican Republic, Peru, Venezuela, Brazil, Mexico, Puerto Rico, China, and India with the aim of understanding the health of older people with dementia in low and middle-income countries. This was conducted in older residents aged 65 years and over and their caregivers, living in eleven geographically defined urban and rural catchment area sites. Details of study methodology and protocols for the 10/66 DRG have been described elsewhere [21]. A full assessment was conducted for all eligible older individuals if they, or their kin, agreed to participate in the survey. The assessment covers a background socio-demographic, health and risk factor interview, a structured clinical mental state assessment, and physical examination.
The present study was based from the 10/66 baseline data from catchment area sites in seven low and middle-income countries including; Cuba, Dominican Republic, Peru, Venezuela, Mexico, China, and Puerto Rico, conducted between February 2003 and June 2009 (in 2003–2006 for Cuba; in 2003–2004 for Dominican Republic; in 2005–2007 for Peru; in 2004–2006 for Venezuela; in 2005–2007 for Mexico; in 2003–2005 for China; and in 2006–2009 for Puerto Rico). The study sites consisted of urban and rural areas. The boundaries of each catchment area were precisely defined, and households were assigned an identification number. Each household was then systematically visited to identify all household members aged 65 years and over who were eligible to participate in the survey. The specific details of the data of each country were have been published elsewhere [22]. The total sample of households with older people from the seven countries was 11,717.
Selected households and participants
This study defined a main caregiver as a person who provides most ‘hands on’ care or the family member who is the main ‘organisational’ caregiver. Data from 1348 households, where the main caregiver provided care for one older person diagnosed with dementia or without dementia in the household, were included in the current analysis. In order to test the research hypotheses, the sample households were classified into two categories; (i) younger caregiver households (where the main caregiver of the household was aged 64 years or lower), and (ii) older caregiver households (where the main caregiver of the household was aged 65 years or over).
Measures of caregiver mental health
Psychological morbidity was assessed through Self-Reporting Questionnaire (SRQ). The questionnaire has been widely used in different populations. There are 20 items covering symptoms of depression, anxiety, and somatised distress [23]. The SRQ detects the presence of non-psychotic psychological symptoms over the past two weeks. It yields a total score that ranges from 0 to 20. Recommended by the WHO [24], higher scores indicating higher psychological morbidity with a cut-off score ≥ 8 is identified as psychological morbidity (coded as 1), whereas scores of less than 8 were coded as 0 for non- psychological morbidity.
Care burden was measured using the Zarit Burden Inventory (ZBI) which is widely cited in caregiver burden literature and has been translated and validated allowing for international comparisons. It was used in the 10/66 pilot studies of the listed countries of this study, strong psychometric properties and cultural relevance were found [18]. The ZBI consists of 22 items including; health, psychological well-being, social life, finances, and the relationship between the caregiver and the older person, with each item being evaluated using a 5-point Likert scale [25]. The cut-off scores from 41 to 88 indicates “a high burden” (coded as 1), and the scores below 41 signify “a low burden” (coded as 0) [25, 26].
Measures of covariate variables
Guided by the Pearlin Stress Process Model [27] and the Yates Stress Process Model [28]. The study sought to control for potential factors including household characteristics, older people’s health status, and socio-demographic status of the caregivers and caregiving hours. These were entered into the model analyses as potential confounding factors, since these variables might affect caregiver’s psychological distress and care burden.
1. Household characteristics
Household size refers to number of household members of the older people household. It is often associated with considerable mental health due to long term care for older people in the household [29].
Number of assets in household out of a possible total list of seven (television, fridge/freezer, mains water, mains electricity, telephone, plumbed toilet, plumbed bathroom) is a proxy of socioeconomic status of the household since it represents more permanent status than does either incomes or consumption [30].
2. Older people’s health status
Dementia refers to the presence of dementia according to the 10/66 Dementia Diagnostic assessments (the CERAD 10-word list recall task, the Community Screening Instrument for Dementia; CSI-D, and the Geriatric Mental State examination; GMS) or DSM-IV dementia criteria. Presenting dementia either measured by the three 10/66 assessments or the DSM-IV was coded as 1, and 0 for non-presence dementia assessed by both measurements.
Functional dependency is the severe difficulty performing basic Activities of Daily Living; ADLs (eating, dressing, toileting, bathing, and walking) assessed by the WHO-DAS developed by WHO. This measure has shown promise in predicting disability level of older people affecting care burden [31]. The severe difficulty with three or more basic ADL was coded as 1, and 0 for the severe problem with lower than three.
Behavioural problems is the severity of 12 behavioral problems including presence of delusions, hallucinations, agitation/aggression, depression, anxiety, irrational euphoria, apathy, disinhibition, irritability, motor disturbance, disruptive nighttime behavior, and adverse appetite/eating change. The measurement is based on the Neuropsychiatric Inventory-Questionnaire (12NPI-Q) score, administered to the main caregiver.
3. Socio-demographic characteristics of the caregivers and caregiving hours
Sex refers to sex of the main caregiver. Sex difference is mentioned frequently in the literature, it is related to kinship role and perception of stress and caregiver burden [32].
Marital status refers to the marital status of the main caregiver at the time of the survey. Theory and empirical findings suggest that there is a relationship between marital status and stress or mental health [33, 34]. It was coded for this analysis as a partnership (currently married or cohabiting) versus non-partnership (single /widowed/divorced/separated).
Education level is the highest level of completed education of the main caregiver. Caregivers with a relatively low education could be assumed to report a higher burden [35]. In this study, it was categorized into primary or lower and higher than primary.
Caregiving hours is the time spent on assisting the older person with ADLs (eating, dressing, toileting, bathing, communicating, using transportation, looking after one’s appearance, and supervising) by the main caregiver in the last 24 hours. The more confining the caregiver task, the more likely that it will create adverse mental health consequences for the caregiver [36, 37].
Statistical Analyses
Descriptive analysis was employed to define the sample, to analyse the distribution of the background variables, and to explore the quantitative level of variables. Tests of significance were performed to examine the association between the household and caregiver background variables, and the health status variables of the older persons with caregiver age group using chi-square tests or Mann-Whitney U tests.
The main strategy for analysis was to apply multivariate models based on binary logistic regression to investigate the effects of caregiver age upon psychological morbidity and care burden. The first model was unadjusted model. All covariate variables (household size, number of household asset, caregiver sex, caregiver marital status, caregiver education, cognitive impairment of older person, functional dependency of older person, behavioral problem of older person, caregiving hour) were controlled in the second model. An odd ratio (OR) and 95% confidence interval (CI) were presented to determine whether a caregiver age is a risk factor for psychological morbidity and care burden, and to compare the magnitude of the effect of caregiver age on the psychological morbidity and care burden. Meta-analysis was performed to obtain pooled estimating one overall OR and 95% CI of the analyses from the different countries, using the inverse-variance weighted (fixed-effect) method. All statistical analyses were performed using STATA/SE 14.0 (StataCorp, Texas, USA).