The Gerontology Research Programme (GRP) in the National University Singapore's Department of Psychological Medicine, was formed to coordinate and facilitate the conduct of multi-disciplinary research on in a wide range of research on ageing and health. The establishment of the Singapore Longitudinal Aging Cohort will provide a large community-based cohort of elderly subjects for observational studies with useful clinical applications. Research synergy is achieved in terms of pooling multi-disciplinary expertise, and combining genetic, biological, environmental, behavioural, social, clinical, and health services approaches to gerontological research.
The SLAS is the principal longitudinal cohort study in GRP. The SLAS is a community-based longitudinal epidemiologic study that aims to increase the understanding of ageing and health, and the factors that influence the ageing process. SLAS seeks to identify the cognitive, biomedical, lifestyle and behavioral, as well as psychosocial risk and protective factors that affect the transition from healthy ageing to functional impairment, illness and death. Participants recruited into SLAS are community-dwelling seniors, aged 55 and above, from various areas in Singapore. Participants are approached door-to-door, are provided detailed information regarding their participation, and are required to provide informed consent before enrollment into the study. The study procedure includes a baseline survey upon enrollment, and participants are revisited on a 3-yearly basis thereafter. Enrolled subjects provide baseline data through structured interviews, physician assessments, laboratory testing, and self-reports of conditions, symptoms, and risk behaviors. Data in the study is collected by trained research staff and nurses. The information to be collected include: Outcomes: Primary Outcomes 4 Main Primary Outcomes 1. Mild cognitive impairment and cognitive functioning 2. Frailty 3. Depression, anxiety (Mood disorder I) 4. Successful and healthy ageing Basic screening followed by diagnostic tests. Cognitive domain functioning. Particpants are screened fro cogntve impairment using global cognitive tests (MMSE and MOCA). An exhaustive neuropsychological assessment battery is also conducted to assess specific cognitive domain functioning of participants. Selected participants that meet screening criteria, thus indicating the presence of possible cognitive impairment, undergo further testing to determine their cognitive functioning status (cognitively normal, mild cognitive impairment, cognitive decline, or dementia), as diagnosed by a panel of geriatricians, in accordance with the DSM-IV-TR criteria for dementia (1), and the MCI Working Group of the European Consortium on Alzheimer's disease criteria (2). Frailty assessment. A battery of measures, including self-report, physical assessments and anthropometric measures, is administered to measure the frailty status of the individuals, in accordance with the Fried et al.'s phenotype criteria (3). Psychiatric assessment. Several self-reported questionnaires are administered to measure the symptomatology of common psychiatric disorders such as depression, among others. Selected participants that meet screening criteria, thus indicating the presence of possible psychiatric disorders, would undergo further testing to determine their mental health state, in accordance with the DSM-IV-TR criteria (1). Successful and healthy ageing. Successful and healthy ageing is determined by a number of self-reported and objective measurements of health which aim to reflect the overall and physical health, cognitive, emotional and social well-functioning (inclusive of life engagement and life satisfaction) of the individual. Secondary Outcomes Physical domain functioning. Self-reported measures as well as physical assessments would be conducted to measure physical functioning, disability and independence in activities of daily living among participants. Health, health services utilization. Data regarding the history of chronic medical conditions and falls, medication use, use of hospital and primary care services and self-rated health. Quality of Life. Self-reported measures would be conducted to measure the quality of life amongst the participants. Mortality. The date of death of participants would be recorded, as well as assessing the Singapore National Registry of Diseases Office (NRDO). Respiratory functioning. Data regarding respiratory functioning would be collected via a spirometry test. Risk and protective factors: Socioeconomic and demographic variables. Information regarding the age, gender, educational status and household income would be collected from the participants via self-report. Medical history. Information regarding the history of selected medical and mental disorders would be collected from the participants via self-report. Biological determinants. Biological specimens (blood and urine) will be analyzed for constituents of interest (e.g. micronutrients, lipid and glucose levels, among others). Pharmacological determinants. The use of pharmacological agents such as anti-inflammatory, cholesterol-lowering and other drugs will be recorded via a self-report measure. Nutrition. Participants would be assessed on their nutritional status and dietary consumption (NSI screening, MNA screening, food frequency, 2-day food diary). The dietary records are analyzed for nutrients of interest and phytochemicals such as B12, B6, folate, curcumin, and other nutritional supplements. Lifestyle and health risk behaviors. Lifestyle behaviors measured would include physical, leisure and social activities engagement duration and frequency. Health risk behaviors measured include the body mass index and other anthropometric measures, smoking, customary physical activity, social and productive activities and alcohol use among participants. Psycho-social data. Self-reported questionnaires are administered to measure life satisfaction, personality, religiosity, social support and asocial network connections for select participants.
Study Type
OBSERVATIONAL
Enrollment
6,183
National University of Singapore
Singapore, Singapore
Dementia and Mild Cognitive Impairment (MCI) Subtyping (Clinical diagnosis of different stages of Dementia)
Dementia and MCI is determined by clinical case conference adjudication where geriatric and psychiatric clinicians convene to determine the diagnosis of a case, utilizing the data from (i) Mini Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) (4-5); (ii) Clinical Dementia rating scale: a 5-point scale used to characterize 6 cognitive and functional domain performance: Memory, Orientation, Judgment \& Problem Solving, Community Affairs, Home \& Hobbies, and Personal Care (6). Information to make each rating is obtained through a semi-structured interview of the patient and a reliable informant (e.g. family member). A higher score indicates increased severity of cognitive impairment; (iii) Informant Questionnaire of Cognitive Decline in the Elderly (IQCODE) - reliable informants report on the cognitive state of the participant (7); (iv) a scale on self-reported subjective cognitive difficulties; and (v) a neuropsychological assessment battery (described below).
Time frame: 20 years - once every 3-4 years
Global and specific domain cognitive functioning ability (Measuring of Global and Specific domain of Cognitive functions)
MMSE (4) and MoCA (5) - 30 items, total scores range from 0-30, higher scores indicate better cognitive functioning. A cut-off of a score of =\<25 is determined as screening positive for cognitive impairment. Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) (8) - measures immediate memory, visuospatial ability, language, attention, delayed memory, and a global cognitive functioning score (a summation of domain scores). A neurocognitive battery measures immediate and delayed memory/learning, visuospatial ability, language, attention, and executive functioning. All domains are calculated by weighted averages of age and education adjusted scores. Tests: (i) Digit Span forward and backwards tasks (9); (ii) Rey's Auditory Verbal Learning Test (10); (iii) Story Memory Test (11); (iv) Brief Visuospatial Memory Test - Revised (12); (v) Boston Naming Test (13); (vi) Clock Reading Test; (viii) Colour Trials 1 and 2 (14); (ix) Block Design task (9).
Time frame: 20 years - once every 3-4 years
Frailty (Measuring the physical and Cognitive Frailty)
Physical frailty was assessed by scores (1 = present, 0 = absent) for five components (shrinking, weakness, slowness, exhaustion, and low Physical Activity (PA)) proposed by Fried et al (3), with the following operational modifications: (i) Shrinking was defined by unintentional weight loss of 4 kg or more in the past 6 months, or BMI less than 18.5 kg/m2, or calf circumference of 31 cm or less. (ii) Weakness was assessed by knee extension strength task in kilogram. (iii) Slowness was assessed by a gait speed test (15). (iv) Exhaustion was measured as a summed score of 3 questions (1-5), "Did you have lots of energy/feel tired (reverse-scored, rs)/worn out (rs)?" (16). A score of \<10 was used to denote exhaustion. (v) Low PA was measured by the LASA PA scale, with those falling below the local gender-specific lowest quintile deemed as low PA (17). Participants are categorised by their total scores as robust (score = 0), pre-frail (score = 1-2), and frail (score = 3-5).
Time frame: 20 years - once every 3-4 years
Depressive symptoms and diagnosis (Measuring of Depressive symptoms and assessment of stages of Depression)
Depressive symptoms are assessed by the 15-item version of the Geriatric Depression Scale (GDS), with a higher score indicating higher depressivity (18). A cut-off score of 5 is used as indicating the presence of depression. Additionally, participants are formally diagnosed by a medically trained research fellow for common mood-related psychiatric conditions using the Structured Clinical Interview for DSM Disorders (SCID) of DSM IV-TR (1), such as Major Depressive Disorder, Minor Depression, Dysthmic Disorder, Mania/Hypomania disorder, Anxiety and panic disorder, Obsessive-compulsive disorder, Post traumatic stress disorder, Psychotic disorder, Mood disorder due to a General Medical Condition and Alcohol abuse disorders, if they screen as positive for depression on the GDS.
Time frame: 20 years - once every 3-4 years
Successful ageing (Measuring the biological, psycho-social and lifestyle factors associated with Successful Ageing)
Successful aging is previously defined (25). Briefly, a score of successful ageing reflects the overall and physical health, cognitive, emotional, social well-functioning, including life engagement \& satisfaction. Physical health and functional well-being was defined as a "good/excellent" self-reported health and IADL independence (20). Cognitive well-functioning and emotional wellbeing was denoted by a minimum MMSE score of 26 (4), and a score below 5 on the GDS (≤5) (18). Social functioning and active engagement in life activities was assessed using a validated questionnaire (26) on participation levels in social, recreational, civic activities, voluntary work, employment/business, and domestic activities. Overall positive life satisfaction was determined using the Life Satisfaction Scale that assessed interest in life, happiness, loneliness, and general ease of living (27). Total summed score ranges from 4 to 18, with the lowest decile indicating a positive life satisfaction.
Time frame: 20 years - once every 3-4 years
Self-reported independent functioning (Measuring the BADL and IADL)
Self-reported Independent Functioning is assessed using the Barthel Index (19) and the Lawton and Brody Instrumental Activity of Daily Living Inventory (20), whereby participants report the degree of dependence on others for several daily and instrumental tasks.
Time frame: 20 years - once every 3-4 years
Physical performance (Measuring the physical performance tests)
Assessed by the Physical Performance Battery which includes the Performance-Oriented Mobility Assessment-Balance and Gait scales (21-22), with a higher score indicating a higher performance in terms of balance or gait; as well as the amount of force displaced in Newtons on a handgrip and knee extension dynamometer. The scores for each of the tests would be combined into a weighted average that reflects overall physical performance.
Time frame: 20 years - once every 3-4 years
Health services utilization (Measuring cost and frequency of health services utilization)
Self-reported frequency of doctor visits over a past 12-month period.
Time frame: 20 years - once every 3-4 years
Quality of life (Measuring the Quality of life SF 12)
Assessed by self-reported scales: (i) EQ5D- 3L - a measure of health-related quality of life that comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. The EQ VAS records the patient's self-rated health on a vertical visual analogue scale (23). (ii) 12-Item Short Form Survey (SF-12) is a 12-item questionnaire used to assess generic health outcomes from the patient's perspective, covering the eight domains of health outcomes: physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional \& mental health (24).
Time frame: 20 years - once every 3-4 years
Mortality (Measuring the risk factors related to mortality)
Date and cause of death data is collected by computerized record linkage with the National Death Registry through the Singapore National Registry of Diseases Office (NRDO).
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Time frame: 20 years
Post-bronchodilation spirometry (Measuring the lung functions tests)
A measurement of lung function which yields the (i) Forced vital capacity - the determination of the vital capacity from a maximally forced expiratory effort; (ii) the FEV1 - volume that has been exhaled at the end of the first second of forced expiration; and the (iii) Peak expiratory flow: The highest forced expiratory flow measured with a peak flow meter. Measurements are made following American Thoracic Society (ATS) criteria for spirometric standardization and procedures, based on the best of four readings, with less than 5% variation in the two best readings. FEV1 is expressed as the percentage of predicted from local norms.
Time frame: 20 years - once every 3-4 years