Measuring age effects

Question 1

Measuring effect of age

Answer 1

Very difficult bc you can’t manipulate age.
- typically the chronological age is used
- majority use cross-sectional design, comparing different age groups in participants that are as similar as possible.
- Some use longitudinal, test multiple times in same person.

Question 2

Cross-sectional design

Answer 2

Age effect derived from differences between persons
who were born in different years/decades.

Downside:
- you don’t actually measure ageing, but age differences.

• Age effect could be due to cohort; effects of generations. Cohorts have different common experiences that may influence their development.

Question 3

Longitudinal desing

Answer 3

Changes between T1 and T2 (or T3, T4 etc.) reflect actual effect of age, so better to estimate effect of passage of time

Rare; very time consuming and expensive

Downsides;
- Often the lesser performing drop out
- Test-retest effects
- Findings may not generalize to other cohorts

Age effects are typically smaller in longitudinal compared to cross-sec

Question 4

Problems with both designs

Answer 4

1. Recruitment bias
   those with poorer health or poorer wealth less likely
   to participate in research, meaning the sample is not representative of population
2. Misclassification bias
   persons in early stage neurodegenerative
   disease misclassified as healthy, may lead to overestimation of age effect