Methods of Human Health Assessment Lab Final

Cross-Sectional Study

collected in a single point in time and cross examines two things like young and old

-relatively quick and easy to conduct

-multiple outcomes and exposures to measure

Cons

- Need large sample size and hard to determine cause and effect relationship

- Lack any information on timing of exposure and outcome relationships and include only prevalent cases

Longitudinal Study

repeated data collected for same subjects over an extended amount of time

Pros:

-can determine patterns since you are looking at the same group over time

Cons:

-time consuming​

-need l​arge sample size

Cohort

identify a group of patients who are already taking a particular treatment or have a shared exposure, follow them over time

Cons

Not as reliable as randomized controlled studies, since the two groups may differ in ways other than in the variable under study

Example: ID a group with a disease and you follow the group for a specific amount of time to see what happens

Observational Study

Draws inferences from sample populations where the independent variable is not under control of the researcher

Case Control Study

Patients who already have a specific condition are compared with people who do not have the condition

"Case vs. Control"

Pros:

-inexpensive and less time-consuming

Cons:

-can be difficult to lay exposures out

Randomized Control Trials

Introduce a treatment or exposure to study its effect on real patients while limiting bias through randomization

Gold standard research design

-single-blind or double-blind

-washes out population bias

Cons:

-very expensive and volunteer only

-hard to maintain subjects to due being invasive

Correlation

Negative (inverse) correlation: when correlation is below 0 and strong is close to -1

Positive correlation: Above 0 and strong is close to 1

Validity

Accuracy; ability of instrument to measure what it is intended to measure

Example: if we were told we were taking a test on nutrition and given a physics test... not valid

Causation

Controls the outcome of something else... one exposure or treatment variable causes a specific outcome

Example: lightening causes thunder

-determined by randomized control trials

With regard to biomedical research, what kind of study can demonstrate causality?

A randomized controlled trial is a planned experiment and can provide sound evidence of cause and effect.

Ex. Baseline data for the group would be recorded to determine the effect of treatment with drug X. One part of the cohort would serve as the experimental group and the second group would serve as a control who would not be administered drug X but would be monitored the same as the experimental group.

Why does correlation not imply causation?

Showing a statistical relationship does not mean that one factor necessarily caused the other.

Reliability

Ability of instrument to repeat measurement (and be similar if not same)

Feasibility

How easy it is able to be accomplished

Sensitivity to change

Detection of an effect that involves change in an outcome due to intervention or developmental effects is mediated by the ability of measures to accurately assess change, a characteristic that is variously termed "responsiveness" or "sensitivity to change"

Ability of instrument to detect changes due to intervention

Describe the anatomy of the heart and blood flow through the heart

Right Heart: Pulmonary circulation

Pumps deoxygenated blood from the body to the lungs

Superior and inferior vena cava→ right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary arteries -> lungs

Left Heart: Systemic circulation

Pumps oxygenated blood from the lungs to the body

Lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta

What are the five major functions of the cardiovascular system?

- Deliver oxygen & nutrients to tissue

- Temperature regulation/fluid balance

- pH balance (Acid/base balance)

- Hormone delivery

- Disease protection/healing

Where does electrical activity originate in the heart?

Impulse originates at the SA node of the heart

Sympathetic nervous system

-carries impulses to SA and AV nodes

-release norepinephrine and facilitates depolarization which increases heart rate

Parasympathetic nervous system

-reaches heart via vagus nerve and carries impulse to SA and AV nodes

-releases acetylcholine that hyperpolarizes the cells and decreases heart rate

How does endurance training affect the parasympathetic input to the heart?

Low resting HR

Elite endurance athlete: 35 beats/min (due, in part,

to high vagal tone)

What is Cardiac Output and what is a typical range?

HR x SV = Q (cardiac output) Total volume of blood pumped from heart per minute

Resting cardiac output ~4.2 to 5.6 L/min

Stroke volume

Volume of blood pumped in one heartbeat

SV = EDV-ESV

EDV = amount of blood remaining in LV at the end of diastole

ESV = amount remaining in LV after systole

How is heart rate measured and what is a typical range?

Measured using electrocardiogram, pulse, or heart rate monitors

-typical range 60-100 bpm

What is tachycardia?

HR > 100 bpm

Define bradycardia

HR < 60 bpm

How do you quickly estimate Max HR?

220 - age

How is Blood pressure measured?

Measured using mercury sphygmomanometer (gold standard), aneroid sphygmomanometer, or automated sphygmomanometer

What is normal systolic blood pressure?

90 - 119

Define normal diastolic range

60 to 79

What is pre-hypertensive range for blood pressure?

systolic = 120-139

diastolic = 80 to 89

Define the BP range for hypertension

140/90

systolic > 140

diastolic > 90

What does the American Heart Association recommend, for the prevention and treatment of high blood pressure?

Eat a well-balanced, low-salt diet

Limit alcohol

Enjoy regular physical activity

Manage stress

Maintain a healthy weight

Quit smoking

Take your medications properly

Work together with your doctor

Why do we assess dietary intake?

- National nutritional monitoring

- Health practitioner counseling

- Diet/health intervention research

- Identifying high-risk groups or geographical areas for disease or food assistance needed

- Evaluate changes in food/agricultural policy and how it is affecting the population

- Assess the progress of health initiatives

- Nutritional education research

24-hour dietary recall

trained interviewer obtains info on all items consumed in the past 24 hours, info can be entered directly into computer or written, face-to-face or via telephone usually visual aids are used to estimate quantities, often done for 3 days within a 2 week period, includes weekends and weekdays

24-hour dietary recall strengths

-low subject burden (less than 20 min)

-unlikely to alter eating behaviors

-participants are usually willing to respond to interviewer

-minimal memory problems

considered one of the best methods for assessing usual dietary intake if multiple recalls are obtained

24-hour dietary recall weaknesses

-does rely on memory some (less than FFQs)

-one recall alone is not able to estimate usual intake of one person

-interviewers should occur on multiple days of the week and seasons of the year (time consuming)

-can be challenging to get complete data on all participants

-under-reporting/ over reporting errors

Food intake records/diaries

subjects record all foods and beverages consumed for 3-4 days, must weigh, measure, or estimate portion sizes, should be provided with 2D portion diagrams, requires that subjects be instructed in how to keep their food intake record

Food intake record strengths

-does not rely on memory

-may be a motivation tool for those in weight loss studies

-can be logistically easier for researchers

food intake record weaknesses

-subjects must be motivated, literate, and trained in the procedure

-recording period must be typical days for the subject (avoid vacations, illness)

-labor-intensive (subject, study personnel) .. not realistic for most large-population studies

-provides info on current diet, not past history of foods consumed

Diet Histories (less common)

provides info on usual diet over an extended period of time with 4 steps

1. collect general data about health habits

2. questions about eating habits

3. crosscheck data with more specific questions

4. 3-day food record

diet history strengths

practical in clinical setting

diet history weaknesses

not used often.... not practical for research

Food Frequency Questionnaire (FFQ)

often used in large epidemiological studies, based on a list of selected foods, assumes long-term diet is more important than dietary intake during a few specific days

FFQ strengths

-simple to administer, self-administered

-can be scanned for analysis

-may be modified or expanded to adapt to changes in the food supply or for different populations

-cost effect.... large samples

-may be more representative of usual intake

FFQ weaknesses

- less precise: must choose from pre-determined portion sizes and foods

- must be validated first in a representative sample of the population of interest

- must be checked by study personnel when self-administered ... missed questions or incomplete questionnaires

- often thought to underestimate kcal intake and overestimate micronutrient intake

-least representative of daily intake

Common self reporting problems

- Under-reporting: normally because of forgotten foods or "sin foods", varies with age, gender, and body composition

--> more of a problem in women than men

- self-reported say what you want to hear or change habits to seem better

When working with human fluids, what should you always assume about a sample?

Always assume a sample is contaminated. This should make you much more careful with the sample

Urinalysis

A routine clinical urine assessment that can detect disease and other conditions

- Tests for UTIs, pregnancy, diabetes

- Primarily tests for urine specific gravity biomarker indicating hydration status

Urinary Specific gravity

Evaluation of water balance and kidney function

Typical range = 1.003 to 1.030

Values closer to 1.00 indicate better hydration status & more dilute urine, while those higher than 1.030 indicate dehydration.

Glycosuria

glucose in the urine

SIADH

syndrome of inappropriate antidiuretic hormone

Decreased values of urinary specific gravity

Relative hydration

What is a Biomarker?

Refers to surrogate endpoints which may be used to predict health outcomes

3 types: RCP

Recovery Biomarker?

Excretion relates to intake

ex. urinary Na, K, N

Predictive biomarker

incomplete recovery, but correlated with intake

ex. urinary sucrose, fructose

3 characteristics that make a good biomarker

- Valid

- Reliable

- Sensitive to change

Why would we be interested in a patient's blood glucose levels?

• Blood glucose assessment can be used in many ways - such as:

Diagnose diabetes, prediabetes, hypoglycemia, and the Metabolic Syndrome.

Forms of Diabetes

A group of disease characterized by high blood glucose concentration resulting from defects in insulin secretion (type 1), insulin action (type II) or both (type II)

Difference in Type 1 and Type 2 diabetes

Type 1 diabetes (T1D), insulin is not made/secreted. Type 2 diabetes (T2D) is a progressive condition, which typically begins with insulin resistance (i.e., the pancreas produces insulin but the cells are resistant to the action of insulin)

Prevalence rates of diabetes and pre-diabetes in US

• The prevalence of prediabetes in the US population is ~30% (1 in 3 people)

• The overall prevalence of diabetes is about 9%. Among adults (18+ years), this rises to ~12%. As you can see in this recent report from the CDC (Table 1), the prevalence of diabetes rises with advancing age. Of those aged 65 years and older, ~25% have diabetes

Fasting blood glucose

Blood glucose measured after 12 hr fast

Hard on patient to be fasted, does not show how body responds to glucose intake

2 hour oral glucose tolerance test (OGTT)

First takes fasting glucose then glucose challenge is given (75g) and blood is drawn 2 hours after challenge

Glycosylated hemoglobin

HbA1c

- An indicator of blood glucose concentrations over the past 8-12 weeks, thus it is used to assess blood glucose control in T2D.

- The units are %, and the principle behind this measurement is that glucose binds to hemoglobin in a concentration-dependent manner

- Healthy people have an HbA1c of 4-6%, and the goal for someone with T2D is below 7%

Casual blood glucose (CBG)

Blood glucose is taken at any time of day, without regard to fasting status

What are some of the complications associated with uncontrolled diabetes?

- Higher risk of glaucoma, kidney disease, neuropathy (i.e., nerve damage, hearing loss, gum disease, and stroke

- Impaired circulation, and result in limb amputations.

According to the results of the Diabetes Prevention Program (DPP) study, how can we reduce our risk of type-2 diabetes? What were some of the key findings of this study?

- Risk can be reduced by exercising 150 min/week & reducing calorie intake by 500-1000 calories a day and reducing fat intake

- The DPP approach included modest weight loss (7%) and 150 minutes of physical activity per week. This risk reduction was greater than a comparison group, which was given the drug metformin.

- The ability of intensive lifestyle modification to reduce diabetes risk (by 58%)

Metabolic syndrome key factors and definition

A condition which is characterized by the presence of three or more cardio-metabolic abnormalities:

1. Visceral obesity/abdominal obesity (determined by waist circumference)

2. low HDL-cholesterol concentration

3. elevated triglyceride concentration

4. elevated blood pressure

5. elevated fasting glucose concentration

Describe coronary heart disease (CHD). What happens to the heart when CHD goes uncontrolled for a long period of time?

Disease involving the network of blood vessels surrounding and serving the heart.

-when plaque builds up in arteries can cause MI

-manifested in clinical end points of myocardial infarction and sudden death

If uncontrolled for a long time can result in such plaque build-up, and hence difficulty pumping blood, that a myocardial infarction occurs

What are the positive and negative risk factors for CHD?

Positive (inc. risk):

Smoking

Hypertension (>140/90)

Low HDL cholesterol (HDL-C; <40mg/dL)

High total and LDL cholesterol (LDL-C)

Family h​istory of CHD

Age (>45, men; >55, women)

Diabetes, prediabetes

Lack of physical activity

Overweight/obesity

Unhealthy diet

Stress

Negative (dec. risk):

HDL >60mg/dL

How is CHD different from cardiovascular disease (CVD)? Why do we care about CVD and CVD risk factors?

CHD is a disease of the arteries around the heart while CVD is a broader term for a variety of conditions affecting the heart and vascular system. (hypertension, congestive heart failure, peripheral vascular disease, and CHD)

Muscular power

product of strength and speed of movement

muscular strength

maximal force we can generate by a muscle

muscular endurance

ability to sustain repeated muscle actions

isokinetic

same speed

muscular fatigue

decrease in the force or power that the involved muscles can produce

complications of uncontrolled diabetes

-glaucoma = 40% higher chance

-kidney disease -high blood pressure overworks the kidneys

-neuropathy - diabetes causes blood vessels in the feet and legs to narrow and harden

-hearing loss - twice as common in diabetic patients

-increase in gum disease

-stroke = 2-4x higher in diabetic patients

how to reduce the risk of type II diabetes

-intense lifestyle changes can reduce by 58% chance

-modest weight loss

4 categories of metabolic syndrome

-insulin resistance

-impaired fibrinolysis

-hypertension

-dyslipidemia

What is Good cholesterol?

HDL - reverse cholesterol transport

What is bad cholesterol?

LDL - major cholesterol transport protein

Which sub-types of cholesterol are considered good and bad?

HDL is good LDL is bad

Small LDL is considered better than larger LDL if both high in number. However, particle amount being lower is more important than particle size

LDL optimal range

< 100 mg/dL

HDL optimal range

> 60 mg/dL

Total cholesterol optimal range

< 200 mg/dL

Why is LDL bad?

initiated in response to an injury to the artery wall from hypertension, homocystine levels, or from oxidized LDL, the injury triggers an inflammatory response, results in development in a fatty streak, which can then lead to fibrous plaque, and then to advanced plaque, which can then lead to obstructions in the artery

How to improve (HDL) good cholesterol

exercise

weight loss

moderation of alcohol

how to reduce bad cholesterol (LDL)

Exercise

-Tic diet: reduce intake of cholesterol, raising nutrients

-reducing saturated fats < 7% of total calories

-dietary cholesterol <200 mg per day

-consuming plant stanols/sterols at 2 grams per day

-->complete w/ cholesterol because they are poorly absorbed in the guy

-increased viscous, or soluble fiber to 10-25 grams per day

--> soluble fiber reduce macronutrient absorption int he gut and increase SCFA

What information is provided by the Framingham risk score? What variables are used in estimating this risk score?

Used to assess 10-year risk of heart attack

- Systolic blood pressure, TC and HDL-cholesterol values, age, gender, smoker

How to measure energy intake

The number of calories needed to maintain a stable body weight (i.e., energy requirements) can be determined by measuring or estimating the number of calories expended.

By using indirect calorimetry we can determine energy expenditure in order to determine an appropriate intake level

What are the components of TEE? How much (%) does each component contribute to the total? What is the most variable component?

Daily total energy expenditure (TEE) is comprised of three components:

Resting energy expenditure (REE; 65%-75%),

the Thermic effect of feeding (TEF; 5%-10%),

and energy expenditure of physical activity (EEPA; 15-30%) (most variable)

REE/RMR

Resting Metabolic Rate/Resting Energy Expenditure

60-70%

-amount of energy required to support viral organ function at rest

TEE and Fat free mass vs. Fat mass

contributes more to total energy expenditure than fat mass

Determinants of resting energy expenditure

body size

body composition

hormonal status

fever

extreme environmental

temperatures

race

sex

age

exercise

Describe the methods by which we can assess energy expenditure

Direct calorimetry, indirect calorimetry, and Doubly labeled water

Direct calorimetry

Measures heat production

indirect calorimetry

Measures oxygen consumption (VO2) and carbon dioxide production (VCO2)

- When volume of air is known and the expired concentrations of O2 and CO2 are known, EE can be estimated

What is RER?

Ratio of VCO2/VO2 based on measures of respiratory gases and ventilation measured at the mouth measured over a particular time period

-range 0.7-1.0

-lower the RER the more fat oxidation, while higher means more CHO oxidation

-greater than 1.0 RER means hyperventilation, lipogenesis, or post exercise buffered CO2 release

What is the typical range for RER? Why does RER fall within this range? What can RER tell us about fuel utilization?

RER: 0.70 - 1.0

- 0.70 is complete fat utilization (metabolism) for energy

- 1.0 means complete glucose metabolism for energy

RQ

Ratio of VCO2/VO2 measured at the tissue

What is a caloric equivalent?

The corresponding caloric expenditure to a given RER value