EVIDENCE LIBRARY
Do Sex Differences After the Same Wine Dose Prove Different Visual Sensitivity?
In a 37-person vision study, women reached higher breath alcohol after the same wine volume. Exposure differences complicate claims about sex-specific visual susceptibility.
No. A difference after the same drinking dose does not establish a difference at the same alcohol concentration. In a 37-person study, women showed greater overall visual deterioration after drinking the same volume of wine as men, but they also reached higher breath-alcohol concentrations. The authors reported that the overall sex difference was no longer significant after adjustment for breath alcohol and other factors.
The DUI relevance is the distinction between dose and exposure. Equal glasses of wine do not guarantee equal concentrations, and an unadjusted group difference cannot automatically be assigned to an inherent difference in visual sensitivity.
The study used a fixed wine volume
Casares-López and colleagues studied 20 women and 17 men in a baseline session and an alcohol session, with session order randomized. Each participant consumed 450 mL of 13.5% red wine over 30–40 minutes, approximately two hours after the last meal.
The investigators measured breath alcohol beginning 30 minutes after consumption and repeated measurements every 20 minutes. They averaged four measurements for each participant. Mean breath-alcohol concentration was approximately 0.38 mg/L in women and 0.30 mg/L in men.
These were measured breath concentrations. The experiment did not analyze blood alcohol, and its illustrative blood-equivalent conversions should not be treated as individually measured BACs. The distinction is explained further in the site’s blood–breath comparison study.
Several aspects of vision changed
The researchers measured contrast sensitivity, perception of halos around a bright source, near and distance stereoacuity, and objective retinal-image quality. Participants used their best optical correction.
After alcohol, the sample showed poorer contrast sensitivity, more visual disturbance around the bright source, reduced stereoacuity and poorer optical-image measures. For example, mean distance stereoacuity changed from approximately 52.7 to 128.3 seconds of arc; a higher threshold indicates poorer discrimination of stereoscopic depth. Near stereoacuity also worsened.
The apparent larger relative deterioration at distance than near was not statistically significant in the reported comparison (p = 0.174). Likewise, the sex differences were not significant for every individual visual measure. The paper’s broad wording should not obscure those null results.
How concentration altered the interpretation
The investigators combined standardized changes into a visual deterioration score. More negative values represented greater deterioration. The unadjusted score was worse in women, who also had higher breath alcohol. Higher breath alcohol was associated with greater deterioration across participants.
The authors then used an analysis including sex, breath alcohol, body mass index and age. They reported a significant contribution of breath alcohol and no significant adjusted sex effect. This supports caution about attributing the unadjusted difference to sex-specific susceptibility at matched exposure.
There is also a reporting limitation: the adjusted sex row contains an F statistic and p value that do not agree mathematically. The published p value and accompanying text describe a nonsignificant adjusted sex effect. Without clarification, that row should not support a precise claim about the size or certainty of an independent sex effect. The modest sample also cannot establish equivalence between sexes.
A composite visual score is not a driving score
The score averaged standardized changes in the measured visual variables with equal weighting. It was useful for describing the experiment’s overall pattern, but it did not measure crash probability or the percentage of driving ability lost.
The reported outcomes did not establish how these participants drove in traffic. Potential relevance to night driving follows from the visual demands involved, not from an on-road result measured in this paper. A claim about a specific collision would require its lighting, hazards, actual exposure and observed driving evidence.
What a DUI interpretation should preserve
This was a small study of selected healthy social drinkers, without a placebo beverage condition. Participants and investigators could know alcohol had been consumed. The many visual comparisons and the source’s reporting inconsistencies further limit sweeping conclusions.
The strongest practical lesson is to identify whether a claim compares equal doses, equal measured concentrations or statistically adjusted results. Those comparisons answer different questions. Sex alone does not determine an individual’s visual performance after a given number of drinks.
The site’s analysis of alcohol-sensitive laboratory tests addresses the additional step needed before a laboratory change can be used to predict driving performance.
Primary source
Casares-López M, Castro-Torres JJ, Ortiz-Peregrina S, Martino F, Ortiz C. Changes in Visual Performance under the Effects of Moderate–High Alcohol Consumption: The Influence of Biological Sex. International Journal of Environmental Research and Public Health. 2021;18:6790. https://doi.org/10.3390/ijerph18136790.