Geographic variation of GI diseases.
R. Fielding Department of Community Medicine, HKU
Learning objectives
• Discuss the relationship between diet & GI disease, giving at least two examples to illustrate this • Give meaningful examples of relationships between poverty & disease & realistic estimates of the scale of the problems arising from this • Give at least two examples of GI diseases arising from different geographic environments • Outline main components of the politics of infantile gastroenteritis • Describe the prevalence of under-nutrition, list most common causes and those most at risk
Introduction
• Both infectious and non-infectious GI diseases vary drastically by geographic location • Main influences:
– socio-economic gradients – diet (foods, preparation & preservation) – political economics.
• Infections contribute to number of important neoplasms (stomach; hepatic)
Public health principle
Cancers: Upper GIT
• Oesophagus: was declining, but remains high in France, Iran, Kashmir, Khazakstan, China. Now increasing in west over past 20 yr: gastric reflux • Stomach: declines worldwide since 1970. Most common Ca in Japan. Japan, Korea & Sabah, Iran & Kashmir, (China: Qinghai, Ningxia) highest (about 26-33% of ca deaths in men). S & SE Asia, lowest prevalence in Asia.
Incidence of gastric cancer /100,000
250 200 Jap . M ale 150 100 50 0 1970 1985 1992 Jap . F em S /h ai m al S /h ai fem H K M ale H K fem
What has changed?
• Diet • Food preservation methods • Increased screening, earlier detection but survival remains poor (50% 5 yr, 21% 10 yr Eckert etal, 1998) • Recognition of Helicobacter pylori too recent to impact on incidence rates.
Cancers: lower GIT
Whereas age standardized incidence of upper GIT cancers have declined, lower GIT cancer incidence has increased. Colorectal cancer incidence in West has increased (E.Europe 11% / 5 years) but mortality declining.
GIT cancer incidence
40 35 30 25 20 15 10 5 0 1974-77 1988-92 O esoph stomach small intes liver colon rectum
Contributing factors
• • • • • • • • Agent, vector, host changes in: diet activity technology social behaviour living conditions tobacco / alcohol use persistence of infectious agents
(Opisthorciasis / Hep B/C and hepatic ca.
Infectious GI diseases
• Increasingly serious problem in developed and well as developing world • Oro-feacal contamination: Major infectious GIDs are water- or food-borne. • Resulting from
– poor hygiene / contamination – inadequate or improperly implemented food regulation
• Many common GI infections not problematic unless immune-compromised
Socio-economics of infantile diarrhoea
• 40,000 infant deaths weekly <5 years old due to diarrhoea. • Principally contaminated water, (not boiled). • Baby milk formula food expensive, therefore made more weakly than required. • Lack of clean oral rehydration > death. • WHO estimates 1.5 million deaths / year avoidable by effective breast feeding protection.
Why do poor mothers use baby formula? • Heavily promoted to doctors and in maternity units • “Free samples” given (which once used prevent baby reverting to breast feeding). Mother then dependant on formula food, which: • uses significant financial resources • cannot be administered properly as most women are illiterate • principle cause of infantile diarrhoea
Poverty and GIDs
Access to uncontaminated water more difficult for poor people. • combined with:
– under or poor nutrition – tobacco / alcohol use – crowded living conditions – lack of toilets, sanitation – exposure to toxins and other carcinogens • greater risk of – diarrhoeal – parasitic diseases
Malnutrition 1: overnutrition
• Excess dietary intake: BMI >25 = overweight • Appears first among affluent then lower class. • In adults high refined protein, carbohydrate and fat intake and too low fruit/veg. • Predisposing factors are malnutrition during foetal and childhood periods. • 30% of Latin Am, Caribb, N.Africa, Pac.Is. and urban Asia
2. Undernutrition
• Insufficient dietary intake. Protein-calorific or trace nutrient (eg iron, zinc). • Prevalent -Famine: war, drought, pests, floods unemployment, dislocation. • Primary (insufficient food); secondary ( parasitosis). • Growth delay, cognitive impairments in children • Risk factor for infectious GIDs, acute Ris and other infections.
• Where people live.
Summary
– tropical / temperate, wet / dry, nomadic / rural / urban, developed / under-developed
• What they do there…
– agriculture/ fishing/ livestock, industry / service / homemaker
• How they can live
– trad/modern, poor/affluent, education / none, available health care, costs, market conditions
• major determinants of their host status and exposure to vectors and agents of GIDs