I. Theories of I. Theories of AgingAging

Biological Theories of AgingPsychological Theories of AgingPsychosocial Factors and Aging

Theories of Aging (cont.)Theories of Aging (cont.)Aging process along with biological and

psychological change and social interaction. There are many theories of aging which describe and interpret the aging process.

However, Bengtson and associates (1999) pointed out two reasons of the lack of integration in theories of gerontology.

1) three different aspects of age (page 43)2) models and theories are not clearly

distinguished.

Biological Theories of AgingBiological Theories of AgingGenetic Theories1.Programmed cell death2.Stochastic process3.DNA repair mechanisms Molecular/Cellular Theories of Aging1.Oxidation2.Lipofuscin3.Heat shock proteinsSystem-Level Theories1.Homeostasis2.Wear-and-tear theories3.Stress

Biological Theories of Aging (cont.)Biological Theories of Aging (cont.)

Genetic Theories1.Programmed cell death (PCD) - the

process of PCD that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, loss of cell membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation.

Biological Theories of Aging (cont.)Biological Theories of Aging (cont.)

Apoptosis is one mechanism for the destruction of cells that have proliferated for specific purposes, such as T-cells in the immune system, and need to destroyed after accomplishing their tasks.

In humans, the number of times somatic cells can replicate is partially regulated by the telomere length.

Apoptosis may be a necessary process to get rid of damaged and cancerous cells (Campisise, 2001)

Biological Theories of Aging (cont.)Biological Theories of Aging (cont.)

2. Stochastic Processes (replication error)Hayflick (1996) stated that there may be

a limited times a cell can replicate without error. This function of random (or stochastic) error is a part of aging process.

DNA is susceptible to damage by a host of environmental factors, such as chemical agents (air pollution, smoking), and radiation, and internal processes such as oxidation.

Biological Theories of Aging (cont.)Biological Theories of Aging (cont.)

3. DNA repair mechanismsIn the process of replication, the are

several different checkpoints through which the cell checks the integrity of the DNA strands. If an error is caught, replication is stopped so that repairs can made.

Biological Theories of Aging (cont.)Biological Theories of Aging (cont.)Molecular/Cellular Theories of Aging1. Oxidation – Free radicals or reactive

oxygen species (ROS) are molecules that are generated during the oxidation process in cell. They are unstable and may interfere with the function of other molecular in the cell.

• The concentration of free radicals increases with age (Sohal & Weindruch, 1996) on page 49.

Biological Theories of Aging (cont.)Biological Theories of Aging (cont.)2. Lipofuscin – accumulated waster products in

aging cells. These waster products normally are disposed via liposomal enzymes, but impaired in aging cells. Lipofuscin blocks cell proliferation and induces cell death, and may be associated with Alzeimer’s disease.

3. Heat shock proteins (HSPs) – having cellular repair mechanism and decelerating aging process. HSPs protect cells from stress and oxidative process by regulating enzymatic processes necessary for repair and apoptosis; others refold damaged proteins into their configuration; they play a major roles in the inflammatory and immune process.

Biological Theories of Aging (cont.)Biological Theories of Aging (cont.)• System-level theories

1. Homeostasis – stability in intra- and extracellular environmental conditions, such as pH balance, blood, pressure, heart rate, temperature, and fluid balance. Homeostasis is a dynamic balance and requires communication among the various organ systems and is largely regulated by the autonomic nervous system via the neuroendocrine system.

It becomes harder to maintain homeostasis as we age: 1) a decline in the production of hormones; 2) the target organs become less responsive; 3) the target organs synthesize less than optimal amount of its product.

Biological Theories of Aging (cont.)Biological Theories of Aging (cont.)2. Wear-and-tear theory – this theory may not

hold for most organ systems. A phrase in gerontology is “Use it or lose it”. Many systems such as cardiovascular system, need regular and moderate exercise to maintain function, and intellectual stimulation may be necessary to the maintenance of cognitive function. However, skeleton joints may be an exception.

3. Stress – is a feeling that's created when we react to particular events. It's the body's way of rising to a challenge and preparing to meet a tough situation. It could be a over-stress or moderate stress.

Psychological Theories of AgingPsychological Theories of AgingThe flowchart in Fig. 3.1 (next slide) presents the intellectual history of the major theories of adult development and traces the origins of the major schools and their development from classical to modern theories.

Psychological Theories of AgingPsychological Theories of AgingClassic Theories1.Ontogenetic models2.Sociogenic modelsCurrent Theories1.Life course theory2.Goal-oriented models3.Postformal operations4.Conscious development

Psychological Theories of Aging (cont.)Psychological Theories of Aging (cont.)Classic Theories1.Ontogenetic models – posit that development

stems from internal forces and consists of stages that are universal, sequential, and irreversible. In these models, change is discontinuous, and characterized by qualitative changes.

a.Erikson (1950) modified Freud’s psychosexual theory of early childhood to a psychosocial model that extended from birth through late life.

b.Jung (1933) focused on adult development, believing that adolescents and young adults develop a persona.

Psychological Theories of Aging (cont.)Psychological Theories of Aging (cont.)2. Sociogenic models – focus on life

course with reference to gender, social class, culture, and cohort, and focus on change in adulthood that varies as a function of social roles and historical context or timing events.

a. Disengagement theory – posits a mutual withdrawal between the individuals and society as one ages.

b. Active theory – argues that more active the older person is, the greater life satisfaction.

Psychological Theories of Aging (cont.)Psychological Theories of Aging (cont.)Current Theories:

Most current theories take some sort of middle ground between strict sociogenic and ontogenetic stands, but they do so with varying emphases on the context, individual goals, and the individual’s choice or ability.

1. Life course theory – Elder (1998) has developed a life course theory which examines the ways in which cohort and historical periods affect the life course structure of individuals (Ex on page 58).

Psychological Theories of Aging (cont.)Psychological Theories of Aging (cont.)2. Goal-oriented models – assume that older

individuals have fewer resources, they must select the goals or activities the wish to pursue and optimize their performance by devoting resources to those particular goals.

3. Postformal operations – more complex cognitive development in adulthood. Not only do people become more cognitively complex with age, but they also may become more emotionally complex. However, the emotional complexity may decrease in late life. Why?

Psychological Theories of Aging (cont.)Psychological Theories of Aging (cont.)4. Conscious development – a

growing sense that adult development is something that individuals do, not something that simply occurs. The development in adulthood consists of increasing mindfulness with three characteristics: 1) the continuous creation of new categories; 2) openness to new information; and 3) an implicit awareness of more than one perspective.

Psychological Theories of Aging (cont.)Psychological Theories of Aging (cont.)Interrelationships among theories: Early theories of adult development

tended to focus on one aspect of adult development, such as personality or social, whereas contemporary theories tend to emphasize multiple influences.

Most current theories emphasize some sort of conscious choice in developmental process. Some theories posit the opportunity for conscious choice as an outcome of developmental processes.

Psychosocial Factors and AgingPsychosocial Factors and Aging

Factors affecting health in late-life:1. Genetic factors may have 0 – 40%

contributions to health.2. Other factors may have 60 – 100%

contributions to health. However, psychological, social and physical health are tightly intertwined.

3. Psychological factors: 1) Personality A and B. 2) How and what we think affect our

health.

II. Understanding II. Understanding Change in Aging Change in Aging

ResearchResearchBasic DefinitionsAge-Related DesignsStatistics for Assessing ChangeStatistics That Predict Change

Basic DefinitionsBasic DefinitionsTwo basic questions in research with

statistical analysis:a. Is there a difference between two or more

groups on a given (dependent) variable?b. Is there an association between two or

more variables?

However, these two types of questions may be asked in different way (page 66).

Different statistical methods may be used to answer these two types of research questions.

Basic Definitions (cont)Basic Definitions (cont)Continuous variables:

Interval (numbers) – numbers that share the characteristics of ordinal and nominal measures but also have the characteristics of equal spacing between categories, such as temperature scales.

Ratio (numbers) – numbers that have all the characteristics of interval numbers but also have an absolute 0 point, such as incomes.

Categorical variables: Nominal (numbers) – numbers used to name attributes of a variable in category, such as male and female.

Ordinal (numbers) – numerical values that assign an order to a set of observation, such as health condition ranked from 1 = very poor to 5 = excellent.

Basic Definitions (cont)Basic Definitions (cont)Bivariate – two variables.Multivariate – more than two variables. Partial correlation – controls for one

variable a, when correlating two other variables (b with c), example on page 68 (education, a, income, b, and health, c)

Regression equation – cause and effect relationship between dependent variable and independent variable(s).

Structural equation modeling (SEM) – simultaneously estimates the relationships among several variables.

Basic Definitions (cont)Basic Definitions (cont)Research designs (experiment)

1. Experimental design – randomization, control and manipulation.2. Quasi-experimental design – control and manipulation. 3. Non-experimental – has none of these three characteristics, naturalistic.

Research designs (subjects)1. Between subject designs (between groups)2. Within subject designs (within groups)

Research question

What design to employ?

Non-experimental

Quasi-experimental

What entities, phenomena, or

variables to study

What type of data to collect?

From whom (or what) to collect data?

At what time points to collect data

In what setting to collect data

Under what condition to collect data?

Single instance

Non-comparative

Retrospective

Figure 7.4 Principal design features (shaded elements) of the Low Back Pain Study (from Sim, J. & Wright, C. (2000). Research in Health Care: Concepts, Designs and Methods. Nelson Thomes Ltd., Cheltenham, United Kingdom)

)

Cross-sectional

Group study

Comparative

Qualitative Quantitative

Naturalistic

Control

Longitudinal

Prospective

Controlled

RandomizationManipulation

Experimental

Research question

What design to employ?

Non-experimental

Quasi-experimental

What entities, phenomena, or

variables to study

What type of data to collect?

From whom (or what) to collect data?

At what time points to collect data

In what setting to collect data

Under what condition to collect data?

Single instance

Non-comparative

Retrospective

Figure 7.4 Principal design features (shaded elements) for quasi-experimental Study (same source).

Cross-sectional

Group study

Comparative

Qualitative Quantitative

Naturalistic

Control

Longitudinal

Prospective

Controlled

RandomizationManipulation

Experimental

Research question

What design to employ?

Experimental Non-experimental

Quasi-experimental

What entities, phenomena, or

variables to study

What type of data to collect?

From whom (or what) to collect data?

At what time points to collect data

In what setting to collect data

Controlled

Under what condition to collect data?

RandomizationManipulation

Single instance

Non-comparative

Longitudinal

RetrospectiveProspective

Figure 6.5 The Rheumatoid Arthritis Study (shaded). It is debatable whether or not the setting for a study such as this should be classed as ‘naturalistic’. Although the situation in which a questionnaire is completed may be a natural one. The process of responding to items on a questionnaire is somewhat unnatural one (same source).

Cross-sectional

Group study

Comparative

Qualitative Quantitative

Naturalistic

Control

Age-Related DesignAge-Related DesignMany studies of the effects of aging use

quasi-experimental design. Because it is nor possible to randomly assign people to different ages.1. Cross-sectional designs – which compare different age groups at one point in time for the studies of age difference. Example?2. Longitudinal designs – which follow people over a certain period (years or decades) of time for the studies of age-related changes. Examples?

Age-Related Design (cont.)Age-Related Design (cont.)

Sequential designs in Table 4.2 (next slide):1. Cohort-sequential designs – can examine age and cohort effects, but confound period.2. Cross-sequential designs – can examine cohort and period effects, bout confound age. 3. Time-sequential designs – can examine age and period effects, but confound cohort.

Age-Related Design (cont.)Age-Related Design (cont.)

In summary, in two of three sequential designs, Parker and Aldwin (1997) had significant age effects but no cohort and period effects. They concluded that the increase in mastery in early adulthood is an age or developmental effect not restrict to a particular cohort or time period.

Statistics That Predict Change (cont.)Statistics That Predict Change (cont.)

Two point designs – researchers want to use baselines data at time 1 to predict some outcome at time 2.

Multiple regression equation:y1 = a + b1x1 + b2x2

Residualized regression equation:y2 - y1 = a + b1x1 + b2x2

Statistics That Predict Change (cont.)Statistics That Predict Change (cont.)Relative risk is a ratio of the probability of the event

occurring in the exposed group versus a non-exposed group.

Consider an example where the probability of developing lung cancer among smokers was 20% and among non-smokers 1%. This situation is expressed in the 2 × 2 table to the right.

Here, a = 20, b = 80, c = 1, and d = 99. Then the relative risk of cancer associated with smoking would be

ratio nonexposed

ratio exposed (RR)Risk Relative

Risk Disease status

Present

Absent

Smoking a = 20 b = 80

Non-smoking

c = 1 d = 99

20)991/(1

)8020/(20

)/(

)/(

dcc

baaRR

Statistics That Predict Change (cont)Statistics That Predict Change (cont)

Analyzing multiple-point longitudinal data

1. Fixed effect model in Figure 4.6

2. Random effect model in Figure 4.7