Disease Statistics — A SWAG guessing game

This morning I was reading an Anchorage Daily News article about how keeping your brain active by working longer delays dementia.   Smack dab in the middle of the article was this dementia factoid:

ABOUT DEMENTIA: About 35 million people worldwide have dementia, and Alzheimer’s is the most common type. In the U.S., about 5 million have Alzheimer’s — 1 in 9 people aged 65 and over.

The numbers didn’t seem right to me.  I immediately suspected wild ass  guessing.  I decided to look at the data a bit more closely.

If there are 35 million people in the world with dementia, and there are 5  million Alzheimer cases in the USA, then….there are probably at least 7 or 8 million cases of dementia in the USA or  about 20% of the world’s dementia cases.  20% of the total is in a 4.7 % population sample.  Does the USA have dementia at 5 times the worldwide average?    Probably not?

I then looked at the CIA life expectancy data.   If enough of the world’s population had a very low life expectancy then the numbers might make sense.  There are places in the world where most people don’t live long enough to get dementia.     Places like Chad (last on the list) or South Africa where the average person doesn’t see their 50th birthday.  But is it statistically significant?  Chad probably gets lost statistically because the population is too small at 11 million.

There are 30 countries in the world where the average person lives less than 60  years (Ethopia is #193 on the list of 223 countries at 60.00 years), but there are also 50 countries in the world where people can expect to live longer than the USA’s 78.62 years.

The data is full of odd little facts.   People in Hong Kong live 7 years longer than do people in the rest of China.   And people in Puerto Rico live longer than the average for the entire USA.   And Italians live longer than any other large group of Europeans.  Go figure.  I wasn’t surprised that Monaco topped the list at over 89 years, but having Macau come in second did surprise me.

I’d expect many  dementia cases in say…Japan (#3) where the average person lives to be 84.

I then went over and looked at the world population totals by country and compared that data to life expectancy data.  I then prepared a table of the 25 most populous countries….and here it is,  the world population top 25:

Country                    Population            Life Expectancy         Life Ex. Rank   Year

China                     1,347,350,000                        74.99                         100          2102 India                      1,210,193,000                         67.48                         163           2011 USA                           313,478,000                         78.62                            51          2012     Indonesia                237,561,000                         71.90                          138          2010  Brazil                        192,376,000                          73.02                         127           2011  Pakistan                 183,000,000                          66.71                          167          2013  Niger                       158,423,000                           54.34                        207          2010 Russia                     143,056,000                           69.85                         152          2012 Bangladesh            142,319,000                           70.36                        150           2011  Japan                       127,650,000                           84.19                             3           2012  Mexico                    112,336,000                           76.86                           72          2010  Philippines             92,340,000                            72.21                         135          2010  Vietnam                   87,840,000                            72.65                        130           2011 Ethiopia                   84,321,000                            60.00                        193           2012 Egypt                        82,019,000                             73.19                        124           2012 Germany                 81,858,000                             80.32                          28            2011     Iran                           76,348,000                             70.62                        149           2012  Turkey                    74,724,000                             73.03                        126           2011 Congo(DROC)      65,966,000                              56.14                       200           2012 Thailand                 65,500,000                             74.05                        115           2010 France                     65,350,000                              81.56                           15           2012  United Kingdom 62,262,000                              80.29                          30           2010   Italy                         59,464,000                              81.95                            11           2011  South Africa         50,586,000                             49.48                         222           2011  South Korea         48,580,000                             79.55                            42          2010

Africa, India, Pakistan and Bangladesh definitely pull the numbers down……but I’d suspect quite a few cases in China and Western Europe…so….I still have doubts.  I wonder if Vodka consumption has anything to do with the Russia numbers?

I still think either the USA number is too high or the rest of the world is too low.  We could have over diagnosing in the USA or ….more likely… we have places where the data is inaccurate.   I still expect SWAG…..and under reporting in the developing world and China.

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