Tag Archives: headlines

How many cases were there?

My interest is always piqued as soon as a news report refers to rates of some disease being “on the rise”.  I’m usually disappointed as I wait to hear the details since often no actual numbers are provided.

Last week a CKOM news brief declared “Heterosexual sex HIV transmission on rise in Sask“.  Really? No details are provided, just quotes from an AIDS Saskatoon coordinator.

What are the actual numbers?*                    2009        2010        2011        2012        2013

Total HIV cases                                                  94            74             66            55              43

Heterosexual sex transmission                   12            11             12             13               9

Injection drug use transmission**            76            56             49             34             28

 

The total number of new HIV cases in the health region is falling and this decrease is primarily among injection drug users.  When the percent of cases associated with one cause decreases, the other causes increase as a percent of the total.  In 2009, 81% of HIV transmission was via IDU and 12% from heterosexual sex compared to 65% and 21% respectively in 2013.

Conclusion?  Heterosexual HIV transmission in the Saskatoon Health Region is not increasing.  A larger percentage of cases are the result of heterosexual sexual contact but there are a smaller number of cases.

I also noted that 68% of cases had heterosexual contact with an injection drug user and 30% of cases had sexual contact with a confirmed or suspected HIV+ person.

*Information from the Saskatoon Health Region’s “HIV Strategy Report 2012-2013” and “Better Health for All Series 5: Rates of HIV declining but more needs to be done“.

** Could be +/- 1 since I used a graph to estimate the percentage in each category.

 

 

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Running for life?

In this week’s health news, running will make you live longer.  Maybe.  Maybe not.

The National Post headline announced that  “Running for five to 10 minutes a day may add three years to lifespans, study suggests“(7/29/2014).  I shouldn’t blame the journalists for exaggerating when the journal article title oversells the study findings as well:  Leisure-Time Running Reduces All-Cause and Cardiovascular Mortality Risk.  (Lee D, Pate RR, Lavie CJ, Sui X, Church TS, Blair SN. J Am Coll Cardiol 2014; 64:472-81.)

The study basics:

  • subjects = 55,137 people who visited a health clinic for a check-up between 1974 and 2002; mostly white, middle to upper class, college educated
  • Data was gathered at the first visit and, where possible, at a second visit whenever that might have occurred.
  • National Death Index used to identify death through 2003.
  • Running was self-reported estimate of activity over previous six months including frequency, duration, distance and speed.

 All of the graphs in the paper illustrate differences in hazard ratio (risk of death in one group compared to another group) rather than differences in actual mortality rates.  The paper provides mortality rates adjusted for baseline age, sex, and examination year so I’ve graphed those rates for comparison.

running and mortality bar chart

We can make predictions based on this information.  Each person-year is observing one person for one year.  So 10,000 person-years could be following 10,000 people for one year, 5,000 people for two years, 1,000 people for ten years or some other combination.  Comparing a group of 10,000 non-runners to a group of 10,000 runners, you would expect to observe 15 more deaths in the non-running group (45 vs. 30).

Another way to describe this is using Absolute Risk Reduction for all-cause mortality.  The ARR = 0.146%.  So, yes, runners did have a 30% lower risk of dying from any cause but the risk of dying was low anyway (0.45% in non-runners) so 30% isn’t really much of a difference.

The big problem with the conclusions stated by the researchers is that association does not equal causation.  They found that runners had lower all-cause mortality.  That does not prove that running reduces mortality.  In fact, in another part of the study, non-runners at the first visit who became runners as of a later visit, did not have lower mortality.  This study observed people who chose to run and chose how much they ran.  Higher duration, frequency, and/or intensity of running did not result in lower mortality.

Which leads to the newspaper headline.  Can running five minutes per day add three years to your life?  Probably not.  The study didn’t even attempt to answer that question.  They estimate that the life expectancy of non-runners  is three years shorter than runners.

This study is not proof that, if you start running, you will live longer.

Math is hard.

When my children were young, math was patterns.  This persists quite far into elementary school with increasing complexity.  At least one CBC reporter is still having difficulty with putting things in order of increasing value.

In an article about a report ranking cities according to how expensive it is for an expat to live there, the author notes that “Vancouver was the 96th most expensive city in which to live, up from 64 in 2013”.

In what world is dropping from a ranking of 64 to 96 considered to be moving “up”?

What’s interesting is that nowhere does the report or the article give any information about how much is actually costs to live in Vancouver for a year.  The information is all relative.  Vancouver may be ranked lower because the cost of living there fell or because the costs in other cities increase.  Unless you are trying to decide which of the ranked cities you should move to, the ranking is rather useless.

There are too many reporters trying to fill up too much space with something.

It’s just a mouse study.

Holy crap.

Here’s the headline that I read today:

Multiple sclerosis drug shows promise in treating post-traumatic stress disorder

No.  No.  No.  A thousand times no.

This article is based on a study of an MS drug in MICE published in Nature Neuroscience.  I have two biology degrees and a PhD in epidemiology and I can’t understand the abstract.  The headline seems to be derived from a chat with the paper’s author:

The possibility that the drug may treat PTSD is “one thing that comes to mind,” Spiegel said in a telephone interview. “That is a potential implication.”

That’s it.

Do not put faith in mouse studies.  Ever.

Junk Food Junk Headline

According to the National Post headline, “Eating junk food before getting pregnant spikes risk of premature birth: researchers”.

No, it doesn’t.

The study “Preconception dietary patterns in human pregnancies are associated with preterm delivery” (JA Grieger, LE Grzeskowiak, and VL Clifton) was e-published ahead of print in the Journal of Nutrition (April 30, 2014).  They concluded that nutrition before pregnancy was associated with pre-term birth.  This was a retrospective, cross-sectional study which means that the 309 pregnant women were surveyed one time about what they ate during the 12 months before they got pregnant.  They were never asked about what they ate during pregnancy although they cite other studies showing that the two are typically similar.

Problem 1:  The results could just reflect that diet during pregnancy affects risk of premature delivery.

After a lot of complicated analyses, the researchers identified three dietary patterns (high-protein/fruit, high-fat/sugar/takeaway, vegetarian-type) and assigned a score to each woman based on how she compared to the average score.  They didn’t categorize mothers into separate groups and compare the incidence of pre-term delivery.  The overall pre-term rate is 10%.  What is the risk for those eating “junk food”?  We don’t know.  This type of analysis could result in complete different findings with a different group of moms.

Problem 2:  Even the researchers acknowledge in their discussion that the results of this study “may not be generalizable to other populations”.

The article and the headline clearly overstate the findings of this study.  I wouldn’t equate an odds ratio of 1.5 to a “spike” in risk.  As long as associations are being used to make dietary recommendations, they could have emphasized that the meat-based, high-protein diet was associated with lower risk of pre-term birth while the vegetarian diet showed no benefit.

Health reporters need to make much more liberal use of the words “may”, “might”, “suggests”, etc. and the headline writers need to stop being so sensationalistic.