Methods of Human Health Assessment Final

cross-sectional study

A study in which a representative cross section of the population is tested or surveyed at one specific time.

cross-sectional study strengths/weaknesses

• Quick, inexpensive, and safe for participants

• may be subject to bias- difficult to create even groups

• Cannot determine cause-and-effect relationships

longitudinal study

a study that observes the same participants on many occasions over a long period of time

longitudinal study strengths/weaknesses

Changes in the outcome variable cannot be attributed to differences between individuals

Eliminates risk of recall bias

Often time-consuming and expensive

Requires commitment and effective resources

Any potential insights from the study can take a long time to be discovered

Participants dropping out is common

observational study

observes individuals and measures variables of interest but does not attempt to influence the responses

observational study strengths/weaknesses

Less hypothetical- captures what people are actually doing (not what they say they will do)

The observer is a human with their own bias- one cannot know what the subject is thinking

No randomization, possible confounding bias

Case-control study

A type of epidemiologic study where a group of individuals with the diseases, referred to as cases, are compared to individuals without the disease, referred to as controls

case-control study strengths/weaknesses

Great for rare diseases/outcomes

Subjects are identified for the study based on their outcome status prior to study

Inexpensive, quick to conduct, and require fewer subjects

Often depend on past records or subjects' memories

Difficult to identify controls

Study is not blind (potential bias with selection)

prospective cohort study

A research study that follows over time groups of individuals who are alike in many ways but differ by a certain characteristic and compares them for a particular outcome.

retrospective cohort study

participants already have a known disease or outcome, and the study looks back to try and determine causation

cohort study strengths/weaknesses

Group sizes can be large

Provide insights into possible relationships between variables

Do not require extensive variable control

Timing of events can be obtained

Less expensive than RCTs

Not randomized and studies may be lengthy

Difficult to control for variables, and often not blind

Outcomes may suggest correlative relationships, but not causative relationships

Randomized Controlled Trial (RCT)

a research study using a true experimental design

RCT strengths/weaknesses

Provides best evidence for given treatment

Able to determine cause-and-effect relationships

Requires a large amount of variable control

May create an artificial environment that may not be generally representative

Randomization techniques used for selection

Sample sizes may be small and RCTs depend on compliance

Possibility of attrition

Can be expensive

Side effects can be dangerous

Correlation vs. Causation

• Causation indicates that one event is the result of the occurrence of an event

• Correlation means there is simply a relationship between variables

Two variables may have a casual relationship, but it is impossible to conclude which variable affects the other

Validity

the extent to which a test measures or predicts what it is supposed to (accuracy)

Reliability

consistency of measurement

feasibility

the state or degree of being easily or conveniently done

sensitivity to change

ability to detect a change when true behavior change occurs

Blood flow though the heart

O2 poor blood -> superior and inferior vena cava -> right atrium -> tricuspid/right AV valve -> right ventricle -> pulmonary valve -> pulmonary trunk -> pulmonary arteries -> lungs -> O2 rich blood -> pulmonary veins -> left atrium -> bicuspid/left AV valve -> left ventricle -> aortic valve -> aorta -> rest of body

5 major functions of the cardiovascular system

1. Delivers O2 and nutrients to cells in the body

2. Removes CO2 and metabolic waste products from cells in the body

3. Transports hormones from endocrine glands to their target receptors

4. Supports body temp. regulation and blood's buffering capability to control pH

5. Maintains proper fluid balance and helps prevent infection from invading organisms

SA node

where electrical activity originates in the heart

Parasympathetic innervation of the heart

Vagus nerve

-carries impulses to SA and AV nodes

-releases Ach, hyperpolarizes cells

-decreases HR and force of contraction

-decreases HR below intrinsic HR (100bpm)

Sympathetic innervation of the heart

Sympathetic cardiac nerves

-carries impulses to SA and AV nodes

-releases NE and facilitates depolarization

-increases HR and force of contraction

-release of epi from adrenal medulla can have similar effect

-increases HR above intrinsic HR during physical/emotional stress

Effect of endurance training on the heart

Elite athletes may have very low resting HRs (35 bpm) due to high vagal tone

Cardiac output

the total volume of blood ejected from the heart per minute

Q = SV x HR

Typical CO = 4.2-5.6 L/min

average CO = 5 L/min

Stroke volume

SV = EDV - ESV

EDV = end diastolic volume

ESV = end systolic volume

Measuring HR

Use ECG, pulse, or HR monitors/watches

-pulse can be measured at radial or carotid artery (don't use your thumb)

Typical resting HR

60-100 bpm

Tachycardia = HR > 100 bpm

Bradycardia = HR < 60 bpm

Max HR = 220-age

Measuring blood pressure

Measured with a sphygmomanometer and stethoscope

Can also use automated sphygmomanometer

Normal BP vs Hypertension

Normal SBP = < 120mmHg

Normal DBP = < 80mmHg

Prehypertensive SBP = 120-129mmHg

Prehypertensive DBP = < 80mmHg

Hypertensive SBP = >130mmHg

Hypertensive DBP= >80mmHg

AHA recommendations for hypertension

-eat a well-balanced diet that is low in salt

-limit alcohol

-enjoy regular PA

-manage stress

-maintain healthy weight

-quit smoking

-take medications properly

-work with your doctor

Importance of assessing dietary intake

Can be used to make associations between intake and disease or risk

Used in diet/health intervention research

Can be used in clinical settings

24 hr dietary recall

-interviewers should be trained in probing methods (5-step multiple pass)

-low participant burden

-very quick to administer

-recalls are usually unannounced, not likely to alter intake

-minimal problems relying on memory

-participants are generally willing to respond

-most accurate method of dietary assessment with correct methodology

-multiple recalls are needed to get a better typical intake

-under- and over-reporting errors can occur

Food intake records/diaries

-individuals should use measuring cups, scale, or diagrams

-does not rely on memory

-can serve as self-monitoring tool and motivation to improve dietary habits

-can be simpler logistically to administer

-individuals must be literate, motivated, and trained

-recording should be on typical days

-more burdensome for participants

-not realistic to use for large population studies

-provides info on recent diet, not past history

-people may alter eating habits while recording

Food Frequency Questionnaire (FFQ)

-relatively simple to administer by researcher or self

-could be scanned for analysis

-can be modified or expanded to adapt to different populations

-cost-effective and can be used in large samples

-may be more representative of usual dietary intake over longer time periods

-less precise

-often will underestimate caloric intake and overestimate micronutrient intake

Common problem with self-reported dietary intake

Possibility of under-reporting

-can be intentional if individual does not want to report consuming socially undesirable foods

-can be unintentional if forgotten items

Assumption for working with human tissues/fluids

-Assume that ALL blood is positive for HIV, HBV, and HCV

-Assume that ALL other human fluids/tissues are also positive

-Assume that ALL individuals are carrying these disease organisms

Handling human tissues/fluids

-Avoid skin contact with blood and other potentially infectious materials

-Avoid eye, nose, and mouth contact with blood and other potentially infectious materials

-Avoid punctures/sticks with contaminated sharp objects

Urinalysis

the examination of urine to determine the presence of abnormal elements

-minimally invasive

-tests for diabetes, UTIs, pregnancy, etc.

-reliable indicator of hydration status

-can be assessed by cloudiness and color

Urinary specific gravity

The density of urine as compared to water; the greater the solute in urine, the higher is its specific gravity

-typically between 1.003-1.030

-higher USG values can indicate dehydration

-values closer to 1.00 indicate adequate hydration

Biomarker

must be: valid, reliable, and sensitive to change

Examples: urinary sodium excretion, sugar intake

Blood glucose importance

Can be used to diagnose diabetes, prediabetes, hypoglycemia, and metabolic syndrome

Diabetes mellitus

a group of metabolic disorders characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both

-T1D: insulin is not made/secreted

-T2D: insulin resistance

Prevalence rates of diabetes

Overall prevalence in the US is 9%

Among adults, 12%

Adults 65+, 25%

High prevalence among American Indian, Alaskan Natives, Blacks, and Hispanics

About 1 in 3 Americans has prediabetes

Measuring blood glucose

Fasting blood glucose (FBG) after 12 hour fast

-snapshot of BG

-does not represent overall BG

2 hr oral glucose tolerance test (OGTT): glucose drink given to determine insulin sensitivity

-only indicates insulin resistance

HbA1C indicates concentrations over past 8-12 weeks

-better picture of long-term BG

complications with diabetes

Glaucoma

Kidney disease

Neuropathy

Hearing loss

Gum disease

Stroke

Impaired circulation

Diabetes Prevention Program findings

we can reduce our risk of T2D by:

-modest weight loss

-reduced calorie intake of 500-1000 kcals/day

-reduced dietary fat intake

-add resistance training (not in study)

Risk reduction greater in DPP than in group given metformin drug

Metabolic syndrome

A syndrome marked by the presence of usually three or more of a group of factors

-high blood pressure

-abdominal obesity

-high triglyceride levels

-low HDL levels

-high FBG

that are linked to increased risk of cardiovascular disease and Type 2 diabetes

Visceral obesity is central feature

Risk factors: overweight/obesity, insulin resistance, race/gender, age

Coronary heart disease (CHD)

damage to the heart from the complete or partial blockage of the arteries that provide oxygen to the heart

manifested in clinical endpoints of myocardial infarction and sudden death

CHD vs CVD

CHD is one FORM of CVD

CVD refers to a variety of conditions affecting the heart and vascular system

CVD includes: CHD/CAD, congestive heart failure, stroke, peripheral vascular disease, hypertension

Dyslipidemia are CHD/CAD risk factors

CVD is the leading cause of death in the US

Positive and negative risk factors for CHD

Positive risk factors:

-smoking

-hypertension (>140/90)

-low HDL cholesterol (<40 mg/dL)

-high total and LDL cholesterol (>130 mg/dL)

-family history

-age (>45 men, >55 women)

-diabetes/prediabetes

-lack of PA

-overweight/obesity

-unhealthy diet

-stress

Negative risk factors:

-high HDL cholesterol (>60 mg/dL)

"good" vs "bad" cholesterol

"Good" cholesterol is HDL

"Bad" cholesterol is LDL

Optimal ranges for total cholesterol, LDL, and HDL

Total: <200 mg/dL

LDL: <100 mg/dL

HDL: >60 mg/dL

Why is LDL bad?

transports cholesterol around body and deposits it in the arteries

Can lead to accumulation in the sub-endothelial space, which can lead to atherosclerosis

Injury caused by hypertension and/or elevated LDL -> inflammatory response -> formation of a lesion -> develops into fatty streak -> fatty streak grows as platelets and monocytes adhere -> oxidized LDL can accumulate -> fatty streak develops into plaque -> fibrous cap forms over plaque, which can occlude vessel or rupture

How can we improve our cholesterol?

Reduce saturated fat intake, and replace it with PUFA or MUFA (do not replace with refined carbs or trans fats)

Maintain healthy diet, reduce intake of refined carbs, avoid excessive alcohol intake

Saturate fat intake of 5-6% total calories

Sodium intake < 2400 mg/day

Framingham risk score

this screening estimates the 10 year risk of having a CHD event.

Includes factors like age, total cholesterol, smoking hx, HDL, SBP, gender, diabetes, known vascular disease

Energy balance

We can measure or estimate expended number of calories

Weight gain occurs when energy intake exceeds expenditure

Weight loss occurs when energy intake is less than expenditure

Components of total energy expenditure

Daily total energy expenditure (TEE):

-Resting energy expenditure (REE) 65-75% of TEE

-Thermic effect of food (TEF) 5-10% TEE

-Energy expenditure of PA (EEPA) 15-30% of TEE

EEPA is the most variable component (determined by duration/intensity)

Primary determinants of REE

REE is the sum of metabolic rates of individual organs and tissues

Factors: body size, body composition, rage, age, sex, hormonal status, fever

Fat-free mass (FFM) contributes more to REE than fat mass

Methods for assessing energy expenditure

Direct calorimeter measures heat production

Indirect calorimeter measures O2 consumption and CO2 production (RER)

-whole room calorimetry (subject stays in room for 24 hrs; air is pulled through the room at known rate and analyzers measure fraction of O2 and CO2 in air)

-metabolic hood (takes about 45 min)

-handheld instrument (takes about 10 min)

RER and RQ

-RER (Respiratory Exchange Ratio) is the ratio of the volume of CO2 exhaled and the volume of O2 inhaled

- RQ (Respiratory Quotient) is measured at the tissues and is the content of CO2/O2 in the blood

RER indicates proportion of fats or carbs being oxidized

Resting RER with mixed diet is about 0.85

Falls between 0.70-1.0

Caloric equivalent

The number of kilocalories produced per liter of oxygen consumed

Depends on RER

Anthropometry

Assesses body dimensions in terms of: length, breadth, circumference, or skinfold thickness

-Anthropometry and body composition are used to assess nutritional status, proper growth in infants/children, outcome of nutritional or other interventions, effects of disease or trauma, or risk or chronic disease

Essential body fat

the minimum amount of body fat necessary for the proper protection of internal organs

-includes fat associated with CNS, bone marrow, cell membranes, and internal organs

Higher in females because it also includes fat in mammary glands and pelvic region

Males: 2-4%

Females: 10-12%

BMI ranges

BMI = weight (kg) / height^2 (m^2)

Underweight = < 18.5

Normal = 18.5-24.9

Overweight = 25.0-29.9

Obesity I = 30.0-34.9

Obesity II = 35.0-39.9

Obesity III = >40.0

Importance of BMI

Reverse causality (many people lose weight due to illness before death)

Overweight/obesity are associated with increased mortality risk

Excess weight is a strong risk factor for developing T2D and CVD

Major limitation: does not account for body composition; individuals with a lot of muscle mass will be misinterpreted as overweight

Converting BMI units

1 inch = 0.0254 meters

1 pound = 0.45392 kg

Body shapes and health outcomes

Lower body/gynoid/pear shape is associated with better health outcomes

Upper body/android/apple shape is associated with more adverse health outcomes

Many of the complications and risks associated with adiposity are more closely related to abdominal fat than obesity

Methods for assessing body composition

Skinfolds

Hydrostatic weighing (first method)

Plethysmography (air displacement/BodPod)- new gold standard

DEXA

Bioelectrical impedance (BIA)

Compartment models of body composition

2-compartment: FM and FFM

3-compartment: bone mass, FM,FFM

4-compartment: FM, total body water (TBW), bone mass, residual mass

5-compartment: adipose tissue, skeletal muscle, bone mass, blood mass, remaining tissue mass

Hydrostatic weighing

Uses 2-compartment model

-body density = body mass/volume

-assumes invariant density of FFM and FM from person to person

-person must blow out all residual lung volume

BodPod Air Displacement

Uses 2-compartment model

-body density = body mass/volume

-assumes invariant density of FFM and FM from person to person

-actually measures pressure changes with injection of air of known volume into chamber

-large body volume displaces air in chamber, resulting in bigger change in pressure

-high cost, and still assumes constant density of FM and FFM

Bioelectrical Impedance Analysis (BIA)

Uses 2-compartment model

A method of assessing body composition by running a low-level electrical current through the body.

DEXA

Uses 3-compartment model

-dual-energy x-ray absorptiometry

-most attenuation through bone, least through FM

Relationship of feasibility and validity

Generally a strong negative relationship between the feasibility of a PA assessment and its validity

As feasibility increases, validity tends to decrease, and vice versa

Least vs most valid method of PA assessment

Least valid: questionnaire

Most valid: doubly labeled water (DLW)

Pedometers vs. Accelerometers

Pedometers:

-tend to be more feasible and less valid than accelerometers

-counts steps/day

-can be used to categorize clients into PA groups

-objective, inexpensive, easy to use, moderate validity, interpretable

-have specific targets for Ex Rx

-don't capture all PA, and are not direct minutes of PA or EE

-limited reactivity

Accelerometers:

-differentiate between walking and running

-use equations to predict EE, time spent being active

-record number of bouts of activity

-high validity and reliability

-sensitive to change, non-reactive

-acceptable cost (kind of)

Steps/day recommendation

10,000 steps/day

-equates roughly to recommended amount of moderate PA (30 min/day)

-exact number was random (nice, round number that is easy to remember)

MET

metabolic equivalents that correspond to kcals burned

1 MET = 3.5 mL O2/kg/min

can be used to describe activity intensity

Electrical path through the heart

SA node, internodal atrial conduction tracts, AV node, Bundle of His, L and R bundle branches, Purkinje fibers

electrical activity measured by ECG

Einthoven's triangle

the triangle around the heart formed by the bipolar limb leads

shape forms an inverted triangle with the heart at the center that produced zero potential when summed

Components of ECG wave

P wave = depolarization of R/L atria

QRS complex = R/L ventricular depolarization

T wave = ventricular repolarization

PR interval = time interval from onset of atrial depolarization to onset of ventricular depolarization

QRS duration = duration of ventricular depolarization

QT interval = duration of ventricular depolarization and repolarization

RR interval = duration of ventricular cardiac cycle

Positive wave deflection (ECG)

Electrical impulse that travels TOWARDS the electrode produces an upright (positive) deflection

-if current flows in same direction as axis of lead, ECG stylus is deflected strongly upwards

-if current flows obliquely to axis of lead, stylus deflection is less strong

-if current flow is perpendicular to axis, there is no deflection

Negative wave deflection (ECG)

Electrical impulse that travels AWAY from the electrode produces a downward (negative) deflection

-if current flow is in opposite direction to axis of lead, stylus is deflected strongly downward

-if current flows obliquely in opposite direction of axis, stylus deflection is less strong

-if no current flow, no deflection of stylus

Respiratory Sinus Arrhythmia (RSA)

variability in heart rate in synchrony with breathing

-R-R interval is shortened during inspiration and prolonged during expiration

-normal variant can be seen in athletes with increased vagal tone

R-R method for HR

1500 / R-R mm (# of small boxes)

Graph paper method for HR

start with R on thick line, and the next 6 thick lines represent HRs of 300, 150, 100, 75, 60, & 50 bpm

estimate HR based on where next R wave lands

6 sec method for HR

number of ECG complexes in a 6 second interval (30 thick lines) multiplied by 10

BEST for irregular rhythms

VO2 max

Maximum oxygen uptake; most oxygen used when working the hardest you can

A measure of the functional capacity of the cardiorespiratory system

Predicts all-cause mortality

Sets upper limit for submaximal work, and can be useful for exercise Rx

Useful for assessing impact of disease status

VO2 max ranges

Sedentary college-aged female: 35-40 ml/kg/min

Sedentary college-aged male: 40-45 ml/kg/min

Joan Benoit (Olympic marathon champion): 78.6 ml/kg/min

Bjorn Daehlie (Olympic cross-country skier): 94 ml/kg/min

5 factors that affect VO2 max

1. Age- decreases in VO2max with age due to age-related reductions in PA levels

2. Gender- about 20% lower in women

3. Level of conditioning- maximum level is reached within 8-18 months of heavy endurance training

4. Specificity of training- the closer the training is to the sport, the greater the improvement in the sport

5. Heredity- accounts for as much as half the variation if VO2max and the individual's response to training

6. Altitude- decreases as altitude increases due to reduction in partial pressure of O2

Absolute vs relative VO2

Absolute: L/min or mL/min

-used when we measure VO2max on cycle ergometer when weight is supported

Relative: ml/kg/min

-used when we measure VO2max when weight is not supported

Measuring VO2max

Maximal exercise testing involves measuring maximal O2 consumption using a treadmill or cycle ergometer with the use of indirect calorimetry

Submaximal testing is often used to predict VO2max because it is easier and does not require the expensive equipment to measure gas fractions and ventilation

Key assumptions for submaximal exercise testing

-Max HR for a given age is uniform (220-age)

-Linear relationship between workload and VO2 (assumes that O2 consumptions of a specific workload is always the same)

-Linear relationship between HR and workload/O2

-A steady-state HR is obtained for each given exercise workload

-Mechanical efficiency (VO2 at a given work rate) is the same for everyone

-HR will vary depending on fitness level between subjects at any given workload

Variables involved with VO2 testing

Positive linear relationship between workload and VO2

Positive linear relationship between HR and VO2

HR is lower at any submaximal workload in endurance-trained state

Heart rate reserve (HRR)

HRR = HRmax − HRrest

5 criteria for a valid VO2max test

1. Plateau in O2 consumption of <150 ml/min with increasing workload

2. Achievement of age-predicted maximal HR

3. RER > 1.1

4. RPE = 17-20

5. Plasma lactate concentration >8.0 mmol

3 of these must be met

Fick equation

VO2 = Q x a-vO2 difference

O2 consumption depends on blood flow (cardiac output) and O2 extraction (difference in arterial and venous O2 content)

Resting VO2:

250 ml/min = 5000 ml/min x (20-15 ml/100 ml)

Maximal VO2:

4560 ml/min = 30,400 ml/min x (20-5 ml/100 ml)

Muscle strength

maximal force that can be generated by a muscle or muscle group

Muscular power

amount of work being done in a movement divided by the time it takes to perform (explosiveness)

-product of strength and speed

-sports: weightlifting, football, gymnastics