Friday 6 December 2013

More binge drinking reports

StatsChat reports on local hype about increased hazardous drinking among women.

A Canadian alcoholism activist is in New Zealand promoting a book. It looks like Alcohol Healthwatch has used the book tour as a hook for a report on female drinking habits in New Zealand. I was a bit surprised to see reporting on big increases in female binge drinking; there's really nothing there in the Ministry of Health data.

Granny Tut-Tut (who recently complained about Key's Nanny State) reported:
Women's alcohol consumption is on the increase, and "we don't really know why", they said, something which was hindered by "gaping holes" in the available research and data. However, they said key target areas for the Government should be pricing, how the alcohol industry markets its products, and availability.
If you don't know why something's increasing, I'm not sure you're well placed for recommending policy interventions. But what's the evidence for increasing female consumption?

 The AHW paper on which the news stories are based says the following:
One recent survey reported that between 1996 and 2012 the rate of hazardous drinking among women remained relatively stable at around 12% of drinkers25. However, other surveys indicate that women of all ages have increased their alcohol intake in the last two decades, and this has been most marked in younger women26 27 28.. The proportion of female secondary students who were current drinkers dropped significantly from 68.5% in the first Youth 2000 survey, to 45.5% in 201229 30. This is consistent with results from the New Zealand Health Survey, where the proportion of 16 to 17-year-old young women drinkers significantly reduced from 79% in 2006/7 to 59% in 2011/1231 32. However, of those secondary students who did drink, 28% had five to nine drinks in an average session in 2001, and 30% in 201233 34. About 10% usually had 10 or more drinks a session in 2012.
Ok. So we have a great big reduction in the proportion of young women who drink and a tiny increase in consumption among those who do drink. Is that our crisis? Seriously? Let's look at their cited sources on increased intake among younger women.

Footnote 25 is the MoH data linked above.

Footnote 26 is Fergusson et al. It is a survey piece offering no independent evidence on time trends. They cite only the Law Commission report on that there's any increasing trend in drinking among young women.

Footnote 27 is Freyer et al's ALAC monitor report 2009-2010. This is a fun one. They specifically say "Comparisons between years should only be made between 2005-06 and 2008-09. Comparisons with 2009-10 should not be made because of a change in the way "Moderate Drinkers" and "Binge Drinkers" has been defined. So keeping that in mind, what do they say about female heavy drinking?
  • There was a substantial drop in the proportion of binge drinkers who were women. In 2005-2006, 55% of all binge drinkers were women; in 2008-09, 31% of binge drinkers were women.
  • Some stats on all youth drinkers first. Table 8 shows a slight increase in youth non-drinkers and, among drinkers, a slight increase in the proportion counted as binge drinkers. Table 10 shows that a decreasing proportion of youth drinkers report having consumed 5+ drinks on the last occasion, though the difference isn't statistically significant. Table 11 shows that the mean number of drinks consumed by youth drinkers has been stable. Table 12 shows that the mean number of drinks consumed by binge drinkers at the last session has had no change from 05-06 through 08-09. Further, Table 14 shows a slight increase in the median age of drinking initiation, though it's still sometime between the 14th and 15th birthdays in both years.
  • Table 15 shows that the proportion of youth drinkers who were female increased from 48% to 51%, but the difference was not statistically significant. An increasing (but not statistically significant) proportion of moderate youth drinkers were female; a stable proportion of binge drinkers were female. 
I can't see any increasing drinking trend among women in the Freyer et al data. Maybe there are unpublished results providing cross-tabs by gender of the trends among all adult drinkers reported in tables 2-4, and maybe those show some kind of crisis among female drinkers, but they're not published and they're not here cited that way either.

Footnote 28 is Huckle et al's summary of trends out of SHORE data. What did they find?

  • At page 44 they note a statistically decreasing trend in drinking prevalence among women both in the past 12 months and from 1995 to 2011, though the difference is very small. The number of past-year drinkers reduced from 85% to 83%.  
  • At page 45 they find, among drinkers, an increase in drinking frequency. Women reported drinking 57 times per year in 1995 and 82 times per year in 2011. In Figure 3, they show that women aged 16-24 years showed the smallest change - eyeballing the picture, the trend for that cohort is entirely flat. Women aged 55-65 showed the largest increase in drinking frequency. However, at page 48 they find that the quantity consumed per drinking occasion went up by a quarter, from 30 ml to 37.5 ml. Young women's consumption increased from 1995 to 2000, declined through 2008, then increased again in 2011, making for a flat overall trend 2000-2011 after an increase from 1995-2000.
  • At page 49 they have the stats on heavy per-session consumption, with a five 15mL drink lower bound. I'll quote: "The proportion of young female drinkers consuming 5+ drinks at least once a week increased from 19% to 28% between 1995 and 2011 (and this was a statistically significant increase). Most of this increase, however, occurred between 1995 and 2000." The SHORE data is pretty much flat from 2000 through 2011; 2011 looks to be slightly below 2000. 
On the whole, the SHORE data is consistent with an increase in heavier drinking among younger women from 1995 to 2000 and a flat trend since then. I would be exceptionally hesitant to describe this as an increase "in the last two decades" because the increase, such as it was, was entirely from 1995-2000. The phrasing makes it sound like we have this increasing trend instead of a level shift. 

So, let's weigh this all up then. Alcohol Healthwatch says that while the MoH data shows stable rates of hazardous drinking among women, three other sources show "women of all ages have increased their alcohol intake in the last two decades, and this has been most marked in younger women". I can't see that their cites support that statement. One shows no significant trend, one just cites the Law Commission, and the last one shows an increase from 1995-2000 and a flat trend since then.

Read and judge for yourself. I can't see that there's any big crisis here.

A few other notes:
  • At page 6, they say that evidence around safe or beneficial levels of consumption has been contested, citing Corrao on cancer. Corrao also was the author of a metastudy showing the cardioprotective effects of alcohol consumption. As always, it ought to be all-source mortality that counts, not any particular condition. 
  • At page 6 they cite BERL saying alcohol causes $5.3b in health and social problem. Note that BERL retracted that figure for a smaller one after I told them that they couldn't count drinkers' excise taxes as a social harm. The other problems in that report were very large.
  • At page 8, they cite a study of residence hall students at Waikato as being representative of drinking habits among all tertiary students. At least where I went to undergrad, the residence hall students drank substantially more than the students who lived at home or elsewhere. Maybe it's different here.
  • At page 9 they claim that 44% of women aged 55-70 drink hazardously. The study they cite uses a lower AUDIT threshold than is standard. Further, the same study says that only 16% of women in that age category engaged in binge drinking over the prior year. Ahem.
  • Their measure of the prevalence of drinking in pregnancy comes from 2001; there've been a lot of public health campaigns since then.
  • Page 9 gives a pile of ethnic differences in drinking and cites trends from 1996 to 2006 but ignores all of the trend data in the 2011 MoH survey. 
The standard disclaimer on alcohol posts now applies. But it didn't apply to these prior posts:

1 comment: