Reduce Your Glaucoma Risk

We’ve talked before about eye health, including:

• Brain Food? The Eyes Have It! ← this is mostly about lutein, as found in leafy greens
• Fatty Acids For The Eyes & Brain: The Good And The Bad
• How To Avoid Age-Related Macular Degeneration

Today we’ll be looking at a large (n=9,973) study into how various factors increase or decrease glaucoma risk, discussing some of the fascinating statistics involved, and boiling it down to some practical takeaways:

The study

The researchers chose to express the increased or decreased risk of glaucoma in the form of logistic regression beta coefficients, which is not how most such papers (or especially their abstracts) do it; the usual way is to express risk as an odds ratio (sometimes called a hazard ratio in the case of risks, but mathematically it’s the same thing). So, for clarity, we’ve taken the logistical regression beta coefficients provided in the paper, converted them to odds ratios (using the formula e^β=OR, since we don’t have the raw data to know the error rate to factor in), and then multiplied the results by 100 to get a percentage in each case.

With that in mind, here’s the list of things you probably can’t change, first:

• Older age slightly increases glaucoma risk: each standard deviation increase in age raises odds by about 5.1%.

Yes, just age. That’s it for relevant (i.e., that were found to have an impact) non-modifiable risk factors.

You may be wondering: personally, I age in years, not standard deviations, so what does this mean for me?

And the answer is: we had to scour the paper for this, but buried in a table in the middle we found that the mean age of those with glaucoma was 62.9 (standard deviation 7.99) and the mean age of those without glaucoma was 60.81 (standard deviation 7.49). Taking this information and taking into account the relevant numbers (9,631 people without glaucoma, and 342 with), means that the global standard deviation was a little over 7½ years. So in practical terms, and rounding a little for simplicity: every 7½ years, your risk increases by about 5%, which means that for every year, your risk increases by about 0.6%.

That might seem like a very small increase, but it has unfortunate implications if you plan to live to 120.

Now, for modifiable risk factors that increased the likelihood of glaucoma:

• High blood pressure increases glaucoma risk by about 72.4%.
• Diabetes increases glaucoma risk by about 47.4%.
• Smoking increases glaucoma risk by 29.5%.
• Alcohol consumption increases glaucoma risk by 26.3%.

Some notes:

• High blood pressure is defined as being 130/80 or higher; see: What Most People Don’t Know About Blood Pressure
• Diabetes is modifiable for most people; see: How To Prevent And Reverse Type 2 Diabetes
• Smoking was recorded as yes/no, not an amount, so even occasional smoking (in the past year) was included as a risk factor
• Drinking was recorded as yes/no, not an amount, so even occasional drinking (in the past year) was included as a risk factor

Finally, some things that reduced risk according to the abstract:

• Not being obese decreases glaucoma risk by 16.8%.
• Being illiterate decreases glaucoma risk by 5.5%.
• Having a low health-related quality of life (HRQoL) score decreases glaucoma risk by 3.9% (per standard deviation drop in score).

Those last two might be confusing, and here we see an issue with data collection, and at first glance this seemed almost certainly a case of reporting bias.

In other words:

• someone who is illiterate may be less likely to get their glaucoma diagnosed
• someone with a low HRQoL might also have less access to healthcare services (and/or poor/negligible/no ability to advocate for themselves), and again, be less likely to get their glaucoma diagnosed.

To learn more about reporting bias and other such problems, see: How Science News Outlets Can Lie To You (Yes, Even If They Cite Studies!)

However! When actually looking at the tabulated data, and reading the discussion in the article, it looks suspiciously like that there was simply a typo in the abstract, as doing our own calculations reveals that those two characteristics (illiteracy and low HRQoL) were, when all was said and done and investigated thoroughly, associated with a higher glaucoma risk.

In contrast, not being obese really was associated with a lower risk, as initially described.

You can read the paper in full here: Incidence and risk factors for glaucoma and its clinical, mental health and economic impact in an elderly population: a longitudinal study

What does this mean in practical terms?

There are a few key takeaways:

• Keep your blood pressure within healthy ranges (ideally under 120/80; the threshold for “high” is 130/80, but 120/80 is already “elevated”, and you don’t want that either; as for how, see: Hypertension: Factors Far More Relevant Than Salt)
• Keep your glucose metabolism healthy (so, eat in a way to avoid diabetes, per How To Prevent And Reverse Type 2 Diabetes; if you are unlucky and have Type 1 Diabetes, this advice still stands, as even if you can’t reverse T1D with your diet, you have even more reason to absolutely want to avoid insulin resistance / keep your insulin sensitivity high)
• Keep your weight within healthy ranges—albeit the association here is most probably heavily mediated by cardio/metabolic disorder (e.g. hypertension/diabetes), rather than the adiposity itself, as well as the considerations we discussed in Fat’s Real Barriers To Health, which in turn are typically correlated with low HRQoL. If you want to lose weight, then here’s what we recommend: How To Lose Weight (Healthily!)
• Don’t smoke
• Don’t drink

For the latter two items, see: Which Addiction-Quitting Methods Work Best?

Take care!