Epidemiology

The intervention study
This training will address the intervention – or experimental study design. For this exercise, you use the dataset ‘Cognition’. The definition of cognition covers all processes necessary in order to be able to process information such as attention, concentration, and memory. You are going to analyze the effect of vitamin B12 and folate supplementation blood levels of vitamin B12, folate, methylmalonic acid, as well as on the cognitive functioning of elderly people with insufficient vitamin B12 levels at baseline. Participants will be randomized to the following treatment arms: 1) B12 and folate, 2) vitamin B12 only, 3) placebo. The randomization step has the objective to achieve an equal distribution of the baseline characteristics across the three intervention groups. These baseline characteristics include age, gender, methylmalonic acid level (MMA: a sensitive marker of vitamin B12 status) and MMSE score (MMSE: Mini Mental State Examination : indicator of cognitive function).

The dataset includes the following variables:
ppnr participant number
SEX Sex; 1 = male, 2 = female
SEXW Male = man, Female = vrouw
AGED age at baseline
LIVING living status: 1= independent, 2= health care facility home
EDUCATION 1= none, 2=primary school, 3=no secondary school, 4=basic secondary school, 5= avarage secondary school, 6=higher secondary school, 7= university
treatmentn treatment arm: 1 = B12 + folate; 2 = B12; 3 = placebo;
MMSE Mini-Mental State Examination: cognitive test to measure dementia
B12_V1 Vitamin B12 (=B12) concentrationat screening (=_V1)
FA_M_V1 Folate(=FA_M) concentration at screening (=_V1)
HCY_V1 homocysteine (=HCY) concentrationat screening (=_V1)
MMA_V1 Methylmalonic acid (=MMA) concentration at screening (=_V1)
B12_V2 Vitamin B12 concentratiesat baseline (=_V2)
FA_M_V2 Folat concentration at baseline (=_V2)
HCY_V2 Homocysteine concentration at baseline (=_V2)
MMA_V2 Methylmalonicacid concentration at baseline (=_V2)
B12_V4 Vitamin B12 concentration at end of study (=_V4)
FA_M_V4 Folaat concentrationat end of study (=_V4)
HCY_V4 Homocysteine concentrationat end of study (=_V4)
MMA_V4 Methylmalonzuur concentrationat end of study (=_V4)
attention_V2 attention score at baseline (=_V2)
execfn_V2 executive function score at baseline (=_V2)
memory_V2 memory score at baseline (=_V2)
praxis_V2 praxis score at baseline (=_V2)
speed_V2 speed score at baseline (=_V2)
attention_V4 attention score at end of study (=_V4)
execfn_V4 executive function score at end of study (=_V4)
memory_V4 memory score at end of study (=_V4)
praxis_V4 praxis score at end of study (=_V4)
speed_V4 speed score at end of study (=_V4)

Preparation of the data
Description of the study population:
1. Check the number of participants in this study and the number of variables of the dataset
2. Enter the characteristics of the total study population and the three individual intervention groups on the reply form.
3. Discuss whether the randomizationprocedure workswell, judging from the distribution of the characteristics of age, gender, vitamin B12, and MMSE score between the three intervention groups?
Studying the effects of supplementation on blood levels and cognitive function:
4. Calculate the absolute (= _V4 – _V2) change in vitamin B12 (B12), folate (FA_M), and MMA (MMA) concentrations after supplementation with placebo, vitamin B12, and a combination of vitamin B12 and folate. Enter the number of participants available for analysis within each treatment arm.
5. Did this intervention the intended effect on the initially low vitamin B12 concentrations?
6. What can you say about the compliance of the participants in this study?
7. Calculate the change in attention, processing speed, and memory after supplementation with a combination of vitamin B12 and folate, vitamin B12, and a placebo. Also fill in the number of available analysis participants per intervention group. What is your conclusion?
8. Test whether the change in cognitive functions in the vitamin B12 + folate group and the vitamin B12 group differ statistically significantly compared to the changes observed in the placebo group.
9. What is your final conclusion?
Response Form Practical Epidemiology BGZ3001
Trainer: Simone Eussen
Week 1: Intervention studies
Name student: …………………………………..
Student numberr: …………………………………..

1. Description of study population
Question 1 Number of participants:
Number of variables:
Question2 Total population Intervention arm:
(n=) B12 + folate (n=) B12 (n=) Placebo (n=)
age*
sex (% female)
MMSE*
Vitamine B12_V2*
Folaat_V2*
MMA_V2*
Question 3 Did the randomisation have the desired outcome?
*average±sd
Q2: Total population: analyze > descripive statistics > descriptives > select variables > paste
Per intervention group: split file, organize items by groups > idem

2. Effect of supplementation on blood levels and cognitive performance
Question 4 Changes in B12, folateand MMA concentrations
Intervention arm
Vitamine B12 + folaet Vitamine B12 Placebo
N Absolute change N Absolute change N Absolute change
B12
Folate
MMA
Q4:Transform > compute data
Question5 Did this intervention have the intended effect on the initially low vitamin B12 concentrations? Explain your response.

Question6 What can you say about the compliance of the participants in this study?
Question7: Mean changes (95% confidence interval) of cognitive performance Conclusion
Interventiegroep
B12 + folate (n=) B12 (n=) Placebo (n=)
Attention
Speed
memory
Q7: 1) Transform > compute data
2) Data > split file > treatment domain
3) Analyze > compare means > paired ttest > options 95%CI

Question8 Mean difference (95%CI) relative to placebo
B12 vs. placebo B12+folaat vs. placebo Vraag 9: Final conclusion
Attention
Speed
memory
Q8: 1) Data > split file > domain
2) Compare means > independent sample ttest, dcognition = testvar, treatment = grouping, define groups

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