Epidemiological Basis of the Hygiene Hypothesis

Question 1

Define Epidemiology (3)

Answer 1

Study of:

1. Distribution of disease
2. Determinants of disease
3. Application of study to control health/manage patients

Question 2

Describe the difference between prevalence and incidence

Answer 2

Prevalence: overall number of diseased individuals within a population at a specific time point

Incidence: Rate of new cases of the disease within a population over specific time period

Incidence to prevalence relationship varies depending on the nature of the disease: Resolving: not much effect of I on P. Non-curable: I contributes to P

Question 3

According to ISAAC, 1998, asthma (wheeze or whistling in the chest in 13-14 yr olds) is more prevalent in: (3)

Answer 3

1. Developed countries
2. Western >> former east
3. English speaking countries

Question 4

Name four broad categories of factors affecting the increase in asthma prevalance

Answer 4

1. Prenatal environment
2. Birth
3. Early childhood environment
4. Adult environment

Question 5

Define the burden of disease

Answer 5

Defined as financial cost, mortality, morbidity. Often measured with QALYs and DALYs, both of which quantify YLDs

QALYs: Quality-adjusted life years; DALYs: Disability-adjusted life years; YLDs: Years lost due to disease

Question 6

Describe some examples of prenatal factors affecting asthma

Answer 6

Maternal smoking

Maternal diet (BMI, fats, anti-oxidants)

Maternal exposure to pollution (allergens)

Maternal stress

Question 7

Describe some examples of adulthood factors affecting asthma

Answer 7

Occupation

Exposure to pollution

Diet

Smoking

Oral contraceptive, HRT, change in hormones (menarche/menopause)

Question 8

Describe some examples of birth factors affecting asthma

Answer 8

Birth weight

Mode of delivery

Question 9

Describe some examples of childhood factors affecting asthma

Answer 9

Allergen exposure (pets, endotoxins, damp, mould)

Infection

Exposure to pollutants

Diet (breast-feeding)

Question 10

Define the hygiene hypothesis theory

Answer 10

The idea that less infections in early development leads to an increased risk of developing autoimmune and allergic diseases

Question 11

Hygiene Hypothesis observation:

• Children exposed to older/other children get _____ infections
• Children with exposure to older/other children get more infections from _____ variety of sources
• Children attendin daycare get more infections than those who do not BUT only makes a difference if the child comes from a _____ family

Answer 11

Hygiene Hypothesis observation:

• Children exposed to older/other children get more infections
• Children with exposure to older/other children get more infections from wide variety of sources
• Children attendin daycare get more infections than those who do not BUT only makes a difference if the child comes from a small family