Methods

Study design: Cross-sectional comprehensive one phase surveys of all residents aged 65 and over living in one or more geographically defined catchment areas in each country.

Catchment areas and sample registration: For urban catchment areas predominantly middle-class or professional areas with high-income earners were avoided. Rural catchment areas were defined by low population density, and traditional agrarian lifestyle. Catchment area boundaries were precisely defined. Mapping was carried out to identify and locate all households, which were allocated household IDs. Households were enumerated to identify possible eligibles (aged 65 and over). Age (and therefore eligibility) was formally determined on revisit for interview. Household and participant details were stored in secure databases. These contained names, addresses, ID numbers, and contact details for neighbours, key informants and friends to facilitate tracing for follow-up. Precision calculations indicated that an overall sample of 2,000 per centre would allow estimation of a typical dementia prevalence of 4.5% with a precision of +/-0.9%. Rural and urban samples of 1,000 each will allow estimation of the same prevalence with a precision of +/-1.2%.

Training/Preparation: Each centre had a project coordinator and 4-10 interviewers. These were generally lay graduates, although Cuba and China used medical doctors. All researchers were rigorously trained in a) study protocol and procedures, b) standard structured interviewing techniques, c) a specific two day training for the Geriatric Mental State structured clinical mental status assessment and the neurological/physical examination; video training materials were provided. Field interviews were regularly checked and supervised. A standardized operating procedures manual covers every aspect of the training and field procedures. All assessments were carefully translated into the relevant local languages (Ibero-American Spanish, Brazilian Portuguese, Tamil and Mandarin).

Assessments:

Interviews were generally carried out in participants' own homes. This was a comprehensive one phase survey - all participants receive the full assessment, lasting approximately 2-3 hours.

1) Outcome - The diagnosis of dementia.
Our previously published 10/66 dementia diagnosis algorithm (1) requires

1. A structured clinical mental state interview, the Geriatric Mental State, which applies a computer algorithm (AGECAT) (2), identifying organicity (probable dementia), depression, anxiety and psychosis and,
2. A cognitive test battery comprising a) the Community Screening Instrument for Dementia (CSI'D) COGSCORE (3) (incorporating the CERAD animal naming verbal fluency task), and b) the modified CERAD 10 word list learning task with delayed recall (4) and
3. An informant interview the CSI'D RELSCORE (3) (10), for evidence of cognitive and functional decline

To allow DSM IV diagnoses and dementia subtype diagnoses also to be applied we include

1. an extended informant interview, the History and Aetiology Schedule - Dementia Diagnosis and Subtype (HAS-DDS) (5), providing more detailed information on onset and course of a possible dementia syndrome
2. the NEUROEX, a brief fully structured neurological assessment with objectified quantifiable measures of lateralising signs, parkinsonism, ataxia, apraxia and primitive 'release' reflexes (6,7).

Final dementia diagnoses is made in two ways. The main dementia outcome ('10/66 Dementia' is defined as those scoring above a cutpoint of predicted probability of DSM IV Dementia syndrome (9) from the logistic regression equation developed in the 10/66 international pilot study, using coefficients from the GMS, CSI-D and 10 word list learning tasks (1). The second approach involves the direct application of research diagnostic criteria for DSM IV and for the following dementia subtype diagnoses; NINCDS-ADRDA Alzheimer's disease criteria (10), NINDS-AIREN vascular dementia criteria (11), and Lewy Body Dementia (12).

2) Blood sample protocol
Fasting blood samples were sought from all participants in all centres other than India, China and Nigeria. 15mls of blood was drawn and distributed as follows;

• one 5ml plastic EDTA for haematology and DNA extraction or storage,
• one 2.5-3ml Fluoride Oxalate bottle for glucose,
• the remainder (approx 8ml) to a clot bottle for biochemistry.

Samples were transferred immediately to the laboratory for haematological and biochemical analysis. Serum obtained from centrifuging the clot sample was divided into aliquots and fresh frozen at -20C. For the DNA collection, in Cuba and Venezuela the EDTA samples are processed and DNA extracted immediately. In Dominican Republic the EDTA sample is frozen at -20C. In Peru, Argentina and Mexico blood is collected onto FTA Elute (Isocode) cards.

3) Genotyping
DNA will be extracted and stored from all seven centres. APOE genotyping will be conducted on all samples, and 60 SNPs informative for African/European ancestry admixture (13) will be genotyped from centres where admixture is relevant (Cuba, Dominican Republic, Mexico, Peru and Venezuela). With 60 SNPs that have average 40% information content for ancestry, we shall be able to estimate three-way individual admixture proportions with a standard error of less than 0.1.

4) Principal exposures - environmental
This information was elicited from participants; with informants also interviewed for those with communication difficulties arising from dementia, severe mental illness, deafness or mutism.

4.1 Sociodemographic status

1. Age, living circumstances (complete list of coresidents with ages and relationships), marital status, education, literacy, religion affiliation and practice, community social activity, social support, social network
2. Socio-economic status - best occupation (self and spouse), current occupational status, income and sources of income, household assets index, food insecurity
3. Migration status - rural or urban residence across the life course.

4.2 Health Status

1. Self reported global health,
2. Self-reported diagnoses (stroke, diabetes, hypertension, heart disease, hypercholesterolaemia, TB, malaria, and cystercicosis) and treatments for these conditions,
3. A self-reported list of 12 commonly occurring physical impairments (14),
4. Activity limitation and participation restriction measured by the WHO-DAS II (15), developed by the WHO as a culture-fair assessment tool for use in cross-cultural epidemiological and health services research,
5. Direct physical assessments - pulse rate, systolic and diastolic resting blood pressure (average of two, sitting and standing), waist circumference, waist/hip ratio, walking test (5 metres walk, turn and return - timed and paces counted),
6. Reproductive status (for women) - menarche, menopause, reproductive period, number of children

4.3 Biological assessments

1. Physical assessments - pulse rate, systolic and diastolic resting blood pressure (average of two, sitting and standing), waist circumference, waist/hip ratio, leg length, height, skull circumference, walking test (5 metres walk, turn and return - timed and paces counted),
2. Haematological tests - full blood count (haemoglobin, haematocrit, differential, MCV, MCH, MCHC),
3. Biochemical tests - fasting glucose, fasting total cholesterol and sub-fractions, triglyceride, albumin, total protein.

These data collected allow us to identify metabolic syndrome according to the criteria proposed by the Third Report of the National Cholesterol Education Program (NCEP - ATP III): presence of three or more of the following; 1. Central obesity as measured by waist circumference: Men > 40 inches, Women > 35 inches. 2. Fasting triglycerides >= 150 mg/dL. 3. HDL cholesterol: Men < 40 mg/dL, Women < 50 mg/dL. 4. Blood pressure >= 130/85 mmHg. 5. Fasting glucose >= 110 mg/dL

4.4 Risk exposures

1. Specific dementia risk factors - head injury with loss of consciousness, family history of dementia, previous depression,
2. Lifestyle and cardiovascular risk factors - alcohol use (volume and frequency currently and before the age of 60), lifetime smoking (never, ever and current smokers and pack year calculation), diet (intake of fish, meat and fruit and vegetables; food insecurity), exercise and activity levels now and in earlier life.

5) Measures of care arrangements, and impact of providing care on caregivers.
These measures have been refined and validated in the 10/66 group's pilot studies (16,17).

1. Economic impact was assessed using the Client Service Receipt Inventory (18), a comprehensive assessment of direct and indirect economic costs for mental health services, adapted for use in the developing world. It elicits information on type and cost of accommodation, income (from all sources) for the person with dementia and the principal caregiver, the occupation of the caregiver, the extent to which the caregiver had cut back on or stopped work in order to provide care, unpaid care provided by family or others, paid care inputs and their costs, and the use (and associated costs) of a variety of health care services; hospital services (inpatient and outpatient); government community health services (general practitioner, nurse, community health worker, other health worker); private doctor; dentist; time and duration of visits, out of pocket costs for the consultations and medications, time taken to travel, cost of travel,
2. Practical impact - contact time between caregiver and cared for person (19), whether or not care was being provided. Time spent by the caregiver in the last 24 hours in specific caregiving activities (20); communicating, using transport, dressing, eating, looking after one's appearance, and supervising,
3. Caregiver perceived strain - the Zarit Burden Interview (ZBI) (21-23) with 22 items that assess the caregiver's appraisal of the impact their involvement has had on their lives,
4. Caregiver mental health (the Self Reporting Questionnaire 20) (24),
5. Behavioural and Psychological symptoms of dementia - the Neuropsychiatric Inventory (NPI-Q) (8).

Data management: All data is entered using EpiData (version 2.0) software. The data entry systems incorporate conditional skips, and interactive checking of data consistency. We have prepared English and Spanish versions. They can be used to administer the interviews direct from a laptop computer, or to enter data collected using pen and paper. Data is extracted into SPSS, and all processing (cleaning, processing of derived variables and running of 10/66, DSMIV dementia and other diagnostic algorithms) is carried out using SPSS batch files. The end result is a cleaned, processed and labelled data set that can be exported into other statistical programs for further analysis.

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