lecture 3

Question 1

What is ‘Incidence’?

Answer 1

• The incidence of a disease is the rate at which new cases occur in a population during a specified period.
• e.g. the incidence of thyrotoxicosis during 1982 was 10/100 000/year in Barrow-in-Fumes compared with 49/100 000/year in Chester

Question 2

What is ‘Prevalence’?

Answer 2

• the prevalence of a disease is the proportion of a population that are cases at a point in time
• the prevalence of persistent wheeze in a large sample of British primary school children surveyed during 1985 was approximately 3%
• the symptom being define by response to a standard questionnaire completed by the children’s parents
• prevalence is an appropriate measure inly in such relatively stable conditions, and it is unsuitable for acute disorders

Question 3

What is a Risk Factor?

Answer 3

• something that increases your chances of getting a disease
• sometimes, this risk comes fromsomething you do
• e.g. smoking increases your chances of developing colon cancer
• therefore, smoking is a risk factor for colon cancer
• other times there’s nothing you can do about the risk, it just exists
• e.g. people 50 and older are more likely to develop colon cancer than people under 50
• age is arisk factor for colon cancer (in fact, it’s the number one risk factor)

Question 4

How is population health a diagnostic aid?

Answer 4

• defining disease (nosology)
• measuring diseases and conditions in populations was foundational to the emergence of modern medicine
• pluralist medicine regarded every individual’s sickness to be unique to that individual in personal circumstances, time and place (similar to complementary medicine)
• from early C19th, new mathematical methods were employed to compare cases and determine that different people were afflicted with the same disease
• first done with patients of tuberculosis
• vital statistics: ‘thermometer of health’, the bookkeeping of death
• Adolphe Qutelet (belgian, 1796 - 1874): began to look at ‘social physics’ or ‘social statistics’ = systematic disease patterns
• concept of the ‘average man’ who could be measured in large numbers and expressed mathematically – average mental, moral and physical characteristics
• disease detective
• why are THESE people sick NOW and in THIS PLACE?

Question 5

What is the epidemiologist asking?

Answer 5

• investigating where, when and who fell sick helps discover what was causing the disease; what the RISKs were

Question 6

Who is Dr John Snow?

Answer 6

• father of infectious disease epidemiology

* mapped cases of cholera in Soho London in 1854 and traced the source back to the water pump in Broad Street

Question 7

What are our population health questions on metabolic syndrome?

Answer 7

• problem: a chronic condition triggered by weight gain
• who has metabolic syndrome
• where do they live
• what are the characteristics of the people who develop it? age/sex/income/ethnicity/social status
• is there something significant about where they live? services/shops
• e.g. tracing obesity trends among U.S. adults: an epidemic
• spreads from the south, particular african americans and hispanic, poor areas

Question 8

What were the obesity stakes by country in 2009?

Answer 8

• US, Mexico, UK on top
• Japan, South Korea on the bottom
• can this be DNA? can you see patterns?

Question 9

Where are more adults obese?

Answer 9

• more adults are obese in more unequal rich countries
• greater amounts of income inequality lead to great levels of obesity
• obesity is a disease of poverty amidst affluence i.e. inequality - the embodiment of being a ‘loser’

Question 10

What is the effect of globalisation?

Answer 10

• destroys employment opportunities for both low and middle class
• not enough disposable income in america means economy may not recover
• high cost of housing in australia
• trickle down not good

Question 11

Can it just be changes in activity levels?

Answer 11

• lazy bums
• have they changed THAT much in just 40 years?
• new evidence not that children are doing less so they put on weight, but that becoming overweight causes them to do less
• many people who are overweight still work all day on their feet, lift weights, use their upper arms
• people perhaps walk less, but the decline in walking happened earlier

Question 12

What happened with the move to civilisation?

Answer 12

• decline in health
• decline in variety of diet - increased amount of carbs
• people got shorter
• lived in their own filth etc
• famine
• sicker with industrial age
• now public health means we live in an age where pathogenic diseases are not our biggest issue

Question 13

Or is it the food?

Answer 13

• human behaviour is not necessarily sufficient to explain the increase in obesity
• early 1970s: high food prices and falling farm incomes threatened the re-election of Richard Nixon
• Earl ‘Rusty’ Butz, US Secretary for Agriculture brokered free trade deal with Malaysia to export cheap, subsidised corn in return for Palm Oil
• US corn growers urged to plant corn from corner to corner
• subsidies destroyed Mexican corn farmers’ exports leading to desperate illegal immigration to US
• currently 200 million migrant workers in the world
• Sugar cane growers (especially Cuba) lost markets to high-fructose corn syrup HFCS55
• far sweeter than cane sugar
• Fast food industry able to cut costs of production of sweet drinks (coca cola, Pepsi), french fries and popcorn leading to a massive increase in affordability of fast food over real food
• now cheaper in US to buy a McDonald’s meal than a pear
• “Becoming obese,” says James Hill, an epidemiologist in the field of obesity, “is a normal response to the American environment”

Question 14

What is corn syrup?

Answer 14

• In use since 1975
• 7 times sweeter than Cane Sugar and therefore when Coca Cola and Pepsi changed from 50/50 HFCS/cane sugar to 100% HFCS, costs fell 20% → lower prices and bigger portions
• ALSO protected frozen food against freezer burn
• kept long-life products tastier
• in baking products (biscuits, buns, bread) → cheaper, tastier and seemingly ‘browned in the oven’
• RESULT: 80% of supermarket products contain HFCS55
• EXPLOSION of prepared foods, processed foods, frozen meals: cheaper, tastier, easier

Question 15

What is the problem with fructose?

Answer 15

• it bypasses the usual complex breaking down processes in the body and goes straight to the liver
• i.e. metabolic shunting
• not seen to be a problem at first, but now some argue that it produces insulin resistance quickly
• HFCS = huge increase in sugar load in body which is not broken down
• Hidden dangers: fruit juice with Children: one orange has its fructose dispersed with fibre
• a glass of fruit juice = SIX oranges, no fibre to break down the sugar and concentrated fructose

Question 16

What is palm oil?

Answer 16

• palm oil imported in deal on free trade
• mid 1970s new technologies made it a viable commercial fat: for frying french fries, margarine, bread, pies
• as dense and saturated as beef lard, more saturated than pig lard
• BUT cheap, ‘good in the mouth’ and above all STABLE – products did not biodegrade on the shelf and lasted longer
• neither did they biodegrade in the body

Question 17

What were the economic results?

Answer 17

• food prices fell dramatically and consumers had cheap, tasty, sweet and fatty food that they did not have to prepare themselves
• animal feed prices fell dramatically as cattle, pigs and chickens were moved to feed on mass produced subsidised corn
• high calories in animals not evolved to eat corn – hypergrowth (chickens matured weeks earlier, cattle grew so much flesh their legs cannot hold them up)
• high profits from food lead to monopolies controlling all food production from farm to supermarket leading to mass industrialised food production, high profitable, lead to factory farming or food lots
• dramatic ecological changes: new deadly salmonella; massed animals living in feedlots knee deep in manure leading to high antibiotic use leading to antibiotic resistance ALSO pollution of groundwater by concentrated animal waste

Question 18

What are changes in products?

Answer 18

• animals fatter but to their detriment
• average US hamburger can contain the homogenised flesh and fat of up to 300 different animals leading to huge increase in contamination and food poisoning (US ~80 million cases pa: ~5000 deaths pa; i.e. ~27% incidence pa; Aust: 42,000 cases pa)

Question 19

What changes have occurred in human diet and human shape?

Answer 19

• Food Inc: the changes to our food in industrialised economies in the last 40 years have been greater than since the rise of agriculture
• the metabolic syndrome epidemic has come from a profound change in the food provided for us by industry and which we find cheap, convenient and satisfying
• is it mass poisoning?