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DASH Diet - Preventive & Social Medicine (PSM)

Definition

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Composition of the DASH Diet

• High in: fruits, vegetables, whole grains, low-fat dairy products, nuts, legumes, poultry, fish
• Low in: saturated fats, cholesterol, red/processed meats, sweets, sodium

Food Group Servings (per day/week):

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Blood Pressure Lowering Effect

Specific Trial Evidence:

• Original 8-week feeding trial: DASH diet reduced SBP/DBP by 5.5/3.0 mmHg compared with the usual US diet
• 6-month behavior change trials: DASH combined with other nonpharmacologic recommendations reduced SBP by ~4 mmHg and DBP by 0.6 mmHg vs. advice-only
• Low-sodium DASH: In adults with SBP ≥150 mmHg, the low-sodium DASH diet produced profound reductions of ~20.8 mmHg in SBP
• With good adherence in clinical practice: expect ~5 mmHg SBP reduction in hypertensives and 2-3 mmHg in normotensives (Harrison's Principles of Internal Medicine, 22nd Ed.)

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DASH + Sodium Restriction (DASH-Sodium)

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Clinical Indications in PSM

• Prehypertension (BP 120-129/<80 mmHg) - lifestyle counseling encouraged
• Stage 1 hypertension (130-139/80-89 mmHg) - primary management
• Stage 2 hypertension (≥140/90 mmHg) - combined with pharmacotherapy

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Beyond Blood Pressure - Additional Health Benefits

• Systolic and diastolic BP
• Total cholesterol and LDL cholesterol
• Body weight and fat mass
• Blood glucose / glycemic control
• Serum inflammatory markers

• Decreased incident CVD: RR 0.80 (95% CI 0.76-0.85)
• Decreased CHD incidence: RR 0.79 (95% CI 0.71-0.88)
• Decreased stroke incidence: RR 0.81 (95% CI 0.72-0.92)

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Key Nutrients in DASH Diet (Mechanism of Action)

• High potassium - counters sodium-induced vasoconstriction
• High calcium (from low-fat dairy) - vasodilatory effect
• High magnesium (from nuts, legumes, grains)
• Low sodium (when combined)
• High fiber and antioxidants from fruits and vegetables
• Low saturated fat - improves endothelial function

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PSM Perspective - Community Application

• The DASH diet components can be purchased at regular supermarkets without need for specialty or higher-priced food products
• It can be customized to meet cultural preferences, individual dietary needs, and lifestyle
• Can be combined with other interventions: weight loss, sodium reduction, increased physical activity
• Behavior change is most successful when patients accept the need, receive counseling, and have adequate socioeconomic support
• Older adults and higher SES groups tend to show greater adherence and success

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Summary Mnemonics / Quick Recall for Exams

• Full form: Dietary Approaches to Stop Hypertension
• BP reduction: 8-14 mmHg systolic (highest among dietary interventions)
• Key features: High fruits/vegetables (8-10 servings), low-fat dairy, whole grains, low saturated fat, low sodium
• First-line for: Prehypertension and Stage 1 hypertension
• Added benefit of low-sodium DASH: up to ~20.8 mmHg reduction in high-baseline SBP

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Genetic Counseling

Definition

• Interpretation of family and medical histories
• Risk assessment
• Education
• Counseling to promote informed choice and adaptation to the risk or condition

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Goals of Genetic Counseling

1. Make a correct diagnosis - often involving laboratory/genetic testing to find pathogenic variants
2. Recommend appropriate treatment and management, including specialist referrals
3. Help the affected person and family understand and come to terms with the nature and consequences of the condition
4. Empower patients to inform other family members of their potential risk
5. Offer testing to provide the most precise risk assessments for other family members
6. Explain approaches available to modify risks

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Who Provides Genetic Counseling?

• Genetic counselors (most common in US, Canada, UK)
• Physicians with genetics expertise
• Genetic nurses

• Referring physicians
• Diagnostic laboratories
• Patients and families

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Common Indications for Genetic Counseling

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Genetic Counseling Case Management Steps

1. Contracting

• Goal-setting and alignment with the consultand

2. Clinical History

• Family history (pedigree construction)
• Medical and developmental history
• Personal and familial genetic testing results
• Laboratory, radiologic, and additional assessments

3. Risk Assessment and Counseling

• Natural history of the condition
• Inheritance patterns and recurrence risk

4. Shared Decision Making

• Genetic testing options and considerations
• Review of management and treatment options
• Referral to appropriate medical providers

5. Psychosocial Considerations

• Psychosocial assessment and support
• Focused counseling
• Connection to community, advocacy, and support resources

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Risk Assessment - Core Component

• Aids in identifying patterns of inheritance
• Establishes rapport with patient and family
• Distinguishes genetic risk factors from environmental ones
• Determines medical surveillance for at-risk relatives

Types of Risk Estimation:

• Autosomal recessive carrier couple: each pregnancy carries 1-in-4 (25%) risk for the affected state
• This risk is independent for each pregnancy (previous unaffected children do not lower the next child's risk)

• Based on population data rather than Mendelian laws
• Example: spina bifida (multifactorial) - recurrence risk ~4% after one affected child
• Example: Down syndrome (trisomy 21) - recurrence risk ~1%, but substantially higher if a parent carries a Robertsonian translocation

• Used when genotypes of key family members are unknown
• Takes prior probability and modifies it based on additional pedigree information
• Essential for X-linked conditions when determining carrier status in women

X-linked Lethal Conditions - Carrier Frequency:

• Carrier frequency in females = 4μ (where μ = mutation rate)
• 2μ by inheritance, 2μ by de novo mutation

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Psychosocial Considerations in Genetic Counseling

• Emotional, cognitive, familial, social, economic, and cultural beliefs

• Grief, guilt, shame, isolation, frustration
• Anxiety and depression related to chronic management

• Ongoing psychosocial assessment throughout the patient's lifespan
• Help during periods of new challenges and transitions
• Identification of individualized resources and support
• Referral for psychotherapy when needed

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Prenatal Genetic Counseling

• Integral part of prenatal testing (Chapter 18 of Thompson & Thompson)
• Part of newborn screening programs
• Covers: amniocentesis, chorionic villus sampling, NIPT, maternal serum screening

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Genetic Counseling for Psychiatric Disorders

• Better understanding of etiology and risk in the family
• Psychological support related to familial risk
• Discussion of the limited role of parenting in causing/preventing psychiatric disorders
• Increased empowerment and self-efficacy
• Early symptom identification and early intervention
• Facilitated meaning-making and coping

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Ethical Principles in Genetic Counseling

1. Non-directiveness - the counselor provides information without directing the consultand toward a specific decision
2. Autonomy - supporting the individual's right to make their own informed decisions
3. Informed consent - before any genetic testing
4. Confidentiality - of genetic information
5. Beneficence / Non-maleficence - acting in the patient's best interests
6. Justice - equitable access to genetic services

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PSM Perspective - Public Health Importance

• Primary prevention: Carrier testing, preconception counseling, avoidance of consanguinity
• Secondary prevention: Prenatal diagnosis, newborn screening programs
• Tertiary prevention: Early management of diagnosed genetic conditions, emergency letters for metabolic crises

• High consanguinity communities (↑ autosomal recessive conditions)
• Advanced maternal age programs (↑ chromosomal anomalies)
• Hereditary cancer syndromes (BRCA, Lynch syndrome surveillance)
• Inborn errors of metabolism - emergency letters with diagnosis and required emergency treatment for conditions like fatty acid oxidation disorders, urea cycle disorders, organic acidurias

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Summary for Exam

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Measles (Rubeola) - Epidemiology, Clinical Features, and Prevention

The Pathogen

• Virus: Measles virus (Rubeola) - member of family Paramyxoviridae, genus Morbillivirus
• Structure: Single serotype, large enveloped RNA virus
• Easily inactivated by dryness, heat, acid, and light
• Only one serotype - facilitates effective vaccine development
• Host range limited to humans - no animal reservoir

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Epidemiology

Transmission

• Route: Inhalation of large-droplet aerosols (airborne + respiratory droplets)
• Infectivity period: Contagion begins before symptoms appear (during prodrome)
• Most infectious: During the prodromal phase (CCC + P)

Contagiousness

• Measles is one of the most contagious infections known
• Basic Reproduction Number (R₀): ~12-18 (among the highest of any infectious disease)
• In a household: ~90% of exposed susceptible individuals become infected
• ~95% of infected people develop clinical disease
• Infectivity rate: 95%

Herd Immunity Threshold

• Requires >95% vaccination coverage to interrupt transmission

Who is at Risk?

Epidemiologic Pattern

• Worldwide distribution
• Endemic: Autumn to spring (indoor crowding)
• Without vaccination: epidemics occur in 1- to 3-year cycles as susceptible populations accumulate
• Incidence peaks in winter and spring
• US: yearly incidence dropped from 300 to 1.3 per 100,000 after vaccination (99.5% reduction)
• Currently: outbreaks in US often initiated by imported cases spreading to unvaccinated individuals

Global Burden

• Still common in developing countries
• Leading vaccine-preventable cause of childhood mortality worldwide
• Case-fatality rate:
  • Developed countries: 0.01-0.1%
  • Endemic areas (sub-Saharan Africa): 5-10%
  • Refugee camps / displaced populations: up to 20-30%
• Pneumonia accounts for 60% of measles deaths

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Clinical Features

Incubation Period

• 7-18 days (commonly 10 days; range 7-21 days)

Phase 1: Prodromal Phase (3-4 days)

Phase 2: Enanthem - Koplik's Spots (Day 2 of prodrome)

• Pathognomonic of measles
• Appear on buccal mucosa opposite the lower molars (also on conjunctiva and vaginal mucosa)
• Described as "grains of salt on a red background" - small bluish-white ulcerations (~1 mm) surrounded by erythema
• Appear ~2 days before the rash (48 hours before rash)
• Last only 24-72 hours (12-48 hours in some sources)
• May be absent if patient presents late in the illness

Phase 3: Exanthem - Measles Rash (Day 4-5)

• Begins behind the ears and on the neck/hairline, then spreads centrifugally downward:
  • Day 1: Face, behind ears, neck
  • Day 2: Trunk and arms
  • Day 3: Legs and feet
• Character: Erythematous maculopapular rash; becomes confluent on face and trunk
• Petechiae may be present
• Patient is sickest on the day the rash appears (fever is highest)
• Rash fades in same order as it appeared (3-4 days after onset)
• May be followed by desquamation, particularly in malnourished children
• Note: Rash may NOT develop in immunocompromised patients (who have the worst outcomes)

Additional symptoms

• Headache, abdominal pain, vomiting, diarrhea, myalgia

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CDC Case Definition of Measles

1. Generalized maculopapular rash of at least 3 days' duration
2. Fever of at least 38.3°C (101°F)
3. Cough, coryza, OR conjunctivitis

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Complications

Respiratory (most common)

Gastrointestinal

• Diarrhea - exacerbates existing undernutrition

Neurological (most feared)

SSPE - Key Details

• Occurs in children infected at <2 years of age
• Progressive course: personality/behavior/memory changes → myoclonic jerks → blindness → spasticity → coma → death (5-15 years after measles)
• Cowdry type A inclusion bodies in neurons
• Abnormally high measles antibody titers in blood and CSF
• Markedly reduced since measles vaccination programs

Immune Suppression (Unique Feature)

• Measles causes profound immunosuppression that lasts weeks to months after recovery
• Mechanism: directly kills T and B cells and monocytes; depresses IL-12 and TH1 responses
• Results in immune amnesia - erases antibody memory to previously encountered pathogens
• Increased susceptibility to other infections (pneumonia, diarrhea) for >2 years after measles
• Suppresses tuberculin skin test (may cause false-negative TST)

Atypical Measles

• Occurs in those who received older killed/inactivated measles vaccine and then exposed to wild-type virus
• More abrupt, intense presentation
• Rash more prominent in distal areas (not cephalocaudal)
• Possible vesicles, petechiae, purpura, or urticaria

Mortality in Special Populations

• Malnourished + vitamin A-deficient children: up to 60% mortality
• US: only 0.1% mortality

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Diagnosis

• IgM: marker of primary infection (absent after reexposure/revaccination)
• Collect specimens during prodrome and up to 1-2 days after rash appears

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Treatment

• No specific antiviral therapy for measles
• Supportive: hydration, antipyretics
• Prompt antibiotics for secondary bacterial infections (pneumonia, otitis media)

Vitamin A (WHO Recommendation)

• Vitamin A markedly reduces morbidity and mortality
• Ribavirin: anecdotal reports in pregnant/immunocompromised patients; not conclusively proven

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Prevention

1. Passive Immunization (Post-Exposure Prophylaxis)

• Human immunoglobulin (Ig) given after exposure
• Within 72 hours: usually prevents infection in immunocompetent
• Up to 6 days after exposure: still prevents or modifies disease

• Children <1 year of age
• Immunocompromised persons (including HIV)
• Pregnant women

• Immunocompetent: 0.5 mL/kg IM (maximum 15 mL)
• Immunocompromised / pregnant: 400 mg/kg IV

2. Active Immunization (Vaccine)

Vaccine Type

• Live attenuated vaccine (Schwarz or Moraten variants of Edmonston B strain)
• Moraten strain ("more attenuated Enders") licensed 1968 in the US; genetically identical to Schwarz strain
• Edmonston-Zagreb vaccine: widely used internationally (passaged in human diploid cells)
• Combined forms: MMR (Measles-Mumps-Rubella) and MMRV (+ Varicella)

Cold Chain Requirements

• Reconstituted vaccine loses potency rapidly
• Inactivated by light and heat
• Loses ~50% potency at 20°C and almost all potency at 37°C within 1 hour of reconstitution
• Strict cold chain maintenance mandatory

Immunization Schedule

• Recommended age: 9 months (in developing countries/high-risk areas) or 12-15 months (in low-risk settings)
• Two-dose schedule recommended (second dose usually at 15-18 months or at school entry)
• Antibodies appear 12-15 days after vaccination; peak at 1-3 months

Vaccine Effectiveness

• Duration of immunity: several decades (possibly lifelong)
• Secondary vaccine failure rate (10-15 years post-vaccination): ~5%
• Decreasing antibody does not mean loss of protection - secondary immune response occurs on re-exposure

Vaccine Safety

• Fever (up to 39.4°C) in 5-15% of seronegative recipients
• Transient rash in ~5%
• Mild transient thrombocytopenia: 1 per 40,000 MMR recipients
• MMR and autism: Multiple large epidemiologic studies and systematic reviews have conclusively refuted any causal association; the original 1998 paper was retracted

Contraindications to Live Measles Vaccine

• Severe immunodeficiency (T-cell defects) - risk of progressive pulmonary/CNS infection from vaccine virus
• HIV with severe immunocompromise
• Pregnancy
• Note: Routine measles vaccination IS recommended in HIV-positive children who are not severely immunocompromised (given severity of wild-type measles in these children)

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Eradication Prospects

• Measles eradication is theoretically possible (single serotype, humans only reservoir, effective vaccine)
• More challenging than smallpox: requires higher population immunity (>95%), more skilled vaccinators, difficult containment (infectious before rash)
• New technology: Microarray patches (MAPs) for vaccine delivery - Phase 1/2 trial (Gambia, 2023) showed similar seroconversion rates to subcutaneous injection (92.9-100% vs 89.7-100%)

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PSM Summary - Key Numbers

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