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CVD > Guided paper > Flashcards

Guided paper Flashcards

1
Q

Background

A

Background

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2
Q

What is the association between CV health and cognitive performance?

A
  • Increased CV health is associated with greater cognitive performance
  • Many risk factors associated with CV health are also risk factors for cerebrovascular health e.g. hypertension – high blood pressure
  • Problem is the reduction of blood flow to brain
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3
Q

What do flavonoids do in the body?

A

increase endothelial function and decreased BP –> increased peripheral blood flow and cerebral blood flow –> which causes (respectively) decreased CVD risk and decreased cerebrovascular disease risk

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4
Q

What is good about polyphenols in cocoa?

A

Beneficial for vascular health, high levels, particularly flavanols within nonfat solids of cocoa

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5
Q

Where are polyphenols in the highest concentrations?

A

o Larger concentrations (5-fold) in DC than MC

o WC contains limited as comprises butter extracted from cocoa liquor and is devoid of non-fat cocoa solids

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6
Q

What have flavanols been associated with?

A

antioxidant and anti-inflammatory effects, reductions in platelet reactivity, aggregation, and adhesion which all promote healthy vascular function and reduce the risk of cardiovascular mortality

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7
Q

What has past research found?

A

flavanol-rich cocoa produce substantial favourable effects on brachial artery (major blood vessel of upper arm) FMD

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8
Q

What does enhanced FMD of brachial artery indicate?

A

is good and can indicate cardiovascular health
o Shechter et al (2014) found <11.3% FMD means pps are more likely to have CV risk factors (higher FMD is better)
o Higher FMD means larger dilation and is partially due to release of NO

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9
Q

What might improved cerebrovascular endothelial function do?

A

reduce the risk of stroke and enhance cognitive function

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10
Q

Objective

A

Objective

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11
Q

What did Marsh et al want to assess?

A

acute effects of consuming different types of chocolate [DC (80% cocoa), MC (35% cocoa), and WC (contained only cocoa fats)] on endothelial and cerebrovascular function in postmenopausal women

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12
Q

What did Marsh et al hypothesise?

A

acute consumption of DC results in improved vascular function, including increased brachial artery FMD and cerebrovascular responses to a standardized cognitive challenge, compared with the consumption of MC.

Also, did not hypothesize changes would be apparent in any measures after the consumption of WC.

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13
Q

Methods

A

Methods

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14
Q

Summarise the methods

A

using a counterbalanced within-subject design, compared acute impact of consumption of energy-matched chocolate containing 80%, 35%, and 0% single-origin cacao on vascular endothelial function, cognition, and cerebrovascular function in 12 healthy postmenopausal women

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15
Q

Describe the participants?

A
  • 12 healthy postmenopausal women
    o mean age 57.3 +/- 5.3 years
    o mean BMI 24.6 +/- 4.6 (normal)
  • Those who smoked, were taking prescribed medications, or previous diagnosis of any cardiovascular disease or cognitive disorder were excluded
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16
Q

Describe the design?

A
  • Repeated-measures crossover design, each participant attend 4 separate laboratory each at the same time of day
  • Familiarisation session, then 3 experimental treatments (order counterbalanced for any order effect)
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17
Q

Describe the chocolate?

A
  • Matched energy content of chocolate between treatments by feeding participants 85 g WC, 87 g MC, and 84 g DC , providing a total of 2099 kJ under each condition
  • Flavonoids (mg/kg) 370 WC, 980 MC, 3600 DC
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18
Q

What happens in the familiarisation session?

A
  • PPS arrive in morning after overnight fast
  • Instructed to complete a food diary and abstain from caffeine, alcohol, chocolate, and vigorous physical activity during the 24 h before each subsequent session.
  • Body mass and height recorded, participants were fitted with a TCD (transcranial doppler: noninvasive ultrasound) to measure baseline resting cerebral blood flow velocity (CBFv: blood supply to brain and speed) for 5 min (no stimulus, eyes open)
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19
Q

Describe the need for a food diary?

A

o FD to record type, portion size, and timing of ingested food and beverages so these could be replicated in the 24 h before each subsequent experimental session
o Meaning prior energy intake matched within subjects between treatments; mean total daily energy intake, quantity of carbohydrates, fats, and proteins consumed determined

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20
Q

What happens in the experimental treatment

A
  • 3 hours long, 1 week apart, same time as familiarisation, after overnight fast and replication of food diary
  • baseline measures of resting blood pressure, resting CBFv and endothelial function (FMD)
  • 15 mins for choc consumption (blindfolded)
  • 30 mins passive rest in temp controlled lab
  • blood pressure, CBFv and endothelial function (FMD) repeated and neuromuscular coupling assessed
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21
Q

Describe the outcome measures: Assessment of vascular endothelial function (which is interface of blood stream and vessel wall)

A

Brachial artery endothelial function was assessed using FMD at baseline and 80 min after chocolate consumption

22
Q

Describe the outcome measures: Assessment of resting cerebrovascular perfusion

A

o CBFv assessed using TCD
o Middle cerebral artery flow velocities measured bilaterally for 5 min (PPS in rested state devoid of stimulation (told to focus on blank whiteboard)
o Measurements were obtained in this way before and 60 min after chocolate consumption

23
Q

Describe the outcome measures: Assessment of neurovascular coupling and cognition

A

o Neurovascular coupling assessed as response of CBFv to increased neural activity induced by cognitive computer-based tasks
o To minimize the learning effect within each treatment, responses during cognitive tasks assessed during the familiarization laboratory visit, these served as baseline data
o Collected 60 min after choc consumption in the experimental treatments

24
Q

Describe the outcome measures: Assessment of blood pressure

A

Beat-to-beat continuous arterial pressure and heart rate traces were recorded for the duration of all sessions

25
Q

Statistical analysis how was effect of choc consumption on outcome measures (FMD, resting CBFv, and responses to CogState testing), assessed before and after consumption?

A

compared between experimental conditions using 2-factor repeated- measures ANOVA

26
Q

When was 2-factor repeated measures ANOVA performed?

A

After changes in cerebrovascular velocity and conductance calculated by subtracting values after administration from baseline values

27
Q

What can be said about the sample size?

A
  • Sample size of 10 individuals would provide >90% power, to detect a 1.4% change in FMD (1% difference in FMD is associated with a clinically meaningful)

o 90% chance of the test having significant results.

o A high statistical power means that the test results are likely valid.

o (higher power = lower chance of type 2 error: accepting null hypoethesis when alternative hypothesis is true)

28
Q

Results: Cerebral blood flow responses before and after chocolate

A
  • measured in 10 pps
  • No significant difference between baseline CBFv, MAP (mean arterial pressure) and cerebrovascular conductance (CVC = CBFv / MAP) between 3 conditions
  • When CBFv data before and after choc compared, interaction effect and main effects for chocolate and time were evident
    o T tests showed significant decreases for MC (p=0.008) and DC (p=0.001)
  • Significant interaction and time effect for CVC data before and after consumption
    o CVC significantly decreased with MC (p=0.018) and DC (p=0.001)
  • No difference for WC with CBFv and CVC
29
Q

Results: MAP and heart rate before and after chocolate

A
  • MAP: no difference at baseline between all 3 and also before and after all 3
  • Heart rate: no difference at baseline between all 3 and also before and after all 3
30
Q

Results: Neurovascular coupling and chocolate

A
  • No significant differences in any of 7 CogState measures when choc conditions compared
  • Cerebrovascular responses (CBFv, MAP, CVC) to 7 cognitive tests assessed from familiarisation to 60 mins after each choc
31
Q

Results: Neurovascular coupling and chocolate - CBFv

A

o 1-factor ANOVA revealed significant differences between conditions in response to cognitive tests (p=0.001)
o T tests show significant decrease during cognitive battery after ingesting WC (p=0.029), MC (p=0.001) and DC (p<0.001) compared with familiarisation
o Also significantly decreased after MC (p=0.048) and DC (p<0.001) consumption compared with WC

32
Q

Results: Neurovascular coupling and chocolate - CVC

A

o After accounting for blood pressure, change in CVC significant between conditions (p=0.001)
o T tests show decrease during cognitive battery after MC (p=0.022) and DC (p=0.003) but not WC
o Also significantly decreased after MC (p=0.006) and DC (p=0.008) consumption compared with WC

33
Q

Results: Neurovascular coupling and chocolate - MAP

A

No sig diff

34
Q

Results: Vascular endothelial function: brachial FMD responses to chocolate

A
  • FMD recorded in all 12 before and 80 mins after choc
  • No difference in baseline FMD between conditions
  • Significant interaction effect between data before and after choc
  • No differences in FMD after WC or MC but significant increase with DC (p=0.002)
  • DC caused higher % of FMD than WC or MC in 9/12
35
Q

Conclusions

A

Conclusions

36
Q

What can be said regarding FMD?

A
  • FMD increased after DC not WC or MC
    o Acute DC consumption increased FMD by 2.4%, which is potentially associated with clinically significant reductions in cardiovascular events
    o Could be due to higher conc of plasma flavanols which have been shown to activate endothelial NO synthase and increase NO production and bioavailability
37
Q

What can be said regarding cognitive function outcomes?

A
  • Cognitive function outcomes did not differ between conditions however cerebral blood flow responses during cognitive tasks significantly lower after DC and MC, not WC

o Consistent decreases in CBFv and conductance after high conc of cocoa (not WC)

o Infers sustained performance in the face of diminished blood flow and hence oxygen

o Based on findings, flavanol mediated NO production in presence of chocolate with high cocoa conc may modify cerebral metabolism and decrease O2 demand in active brain regions.

38
Q

MAIN CONCLUSION

A

SO consumption of chocolate with high concentrations of cocoa can enhance vascular function and increase cerebrovascular efficiency in postmenopausal women

39
Q

Strengths: other studies

A
  • Results correspond with previous acute studies that observed 3-4% increase after DC and 0-2% decrease after WC
  • Agrees with study with differing conc of flavanols in cocoa beverage form that found no effect on performance in cognitive task
40
Q

Strengths: design

A
  • Matched for energy unlike other studies
  • Disclosed nutritional composition
  • Decreases in CBFv persisted after normalising for concurrent blood pressure change, cannot be attributed to impact on systemic hemodynamics
  • The first to control type, composition and energy content of chocolate used (manufactured specifically for study), conditions counterbalanced, PPS blinded, fasted, avoid certain foods, food diary
  • Use of single origin cacao bean ensured constituents (e.g. flavonoid breakdown – catechin, epicatechin and proanthocynanin conc) were consistent
  • Techniques of assessment of peripheral ad cerebral vascular responses well validated
41
Q

Strengths: PPS

A
  • Is postmenopausal so avoids confounding impact of menstrual cycle on vascular endothelial responses in younger women

o Premenopausal women have a lower incidence of cardiovascular disease, which may partly be due to a protective effect of estrogen (higher when younger) on endothelial function

Excluded other risk factors

42
Q

Strengths: conflicts of interest

A
  • No conflicts of interest as chocolate purchased at full cost
43
Q

Weaknesses: other studies

A
  • Contradicts Sorond et al who found no change in elderly after cocoa beverage, BUT could be due to different populations or methodology e.g. no different conc of cocoa or a control.
  • Contradicts Field et al who found DC increased cognitive performance of young adults compared to WC BUT did not assess conc responses and likely to have used differing cocoa beans with different polyphenols
44
Q

Weaknesses: design

A
  • TCD limitations of not deriving diameter measures and using velocity as surrogate for flow
45
Q

Weaknesses: PPS

A
  • Is postmenopausal women so can only be applied to them

- Relatively small sample size (e.g. could be individual genes), although conc response findings internally consistent

46
Q

Weaknesses: applications

A
  • Should not encourage excess consumption as impact of repeated acute treatment not established
47
Q

Weaknesses: conflict of interest

A
  • Large proportion (62%) of published studies on impact of chocolate on cardiovascular endpoints are funded by chocolate confectionary industry
48
Q

Weaknesses: other limitations

A
  • Could be in the food matrix or individual genes
49
Q

Further research?

A
  • Further to address flavanol mediated NO production in presence of chocolate with high cocoa conc may modify cerebral metabolism and decrease O2 demand in active brain regions.
  • Focus on additional measurements including MRI based cerebral blood flow and arterial diameter measures
50
Q

Why postmenopausal women?

A
  • At risk of CVD, stroke and cognitive decline
  • Premenopausal women have a lower incidence of cardiovascular disease, which may partly be due to a protective effect of estrogen (higher when younger) on endothelial function

CVD (12 decks)

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