Health Survey for England: Changes to alcohol conversion factors used to measure alcohol consumption Methodological change notice

The Health Survey for England (HSE) is a long running series of surveys. It monitors trends in the nation’s health and care, providing information about adults aged 16 and over, and children aged 0 to 15, living in private households in England. It estimates the proportion of people in England who have health conditions and the prevalence of risk factors and behaviours associated with certain health conditions and how prevalence varies within the population. Each survey includes core questions about, for example, alcohol, general health, smoking; measurements such as height, weight, and blood pressure; and analysis of blood and saliva samples. In addition, there are question modules on specific topics that vary from year to year.

The surveys measure alcohol consumption by asking participants about what beverages have drunk and converting drinks to alcohol units. 

The way alcohol consumption is measured in surveys needs to adapt to changes in real-world alcohol consumption. In June 2018, the alcohol theme group of the English Health Statistics Steering Group (EHSSG) hosted a workshop with alcohol consumers and experts to consider the need for updating and further harmonisation of government survey questions relating to alcohol consumption. The workshop concluded that there was a need to consider updating the alcohol product list and conversion table used in the HSE and whether new questions were needed to reflect current alcohol drinking behaviours and policy concerns. The HSE Alcohol Working Group was formed in response to this and subsequently made recommendations including updating the alcohol unit conversion factors.

Measuring alcohol consumption

The Health Survey for England asks participants about drinking alcohol with questions covering: 

Frequency of drinking in the last 12 months (including those who never drink);

The frequency of drinking different types of drink and the amounts of each drunk on a typical day in the last 12 months (providing average weekly consumption estimates);

Number of drinking days in the last week; 

The amounts of different types of alcohol drunk on the day they drank most in the last week (‘maximum amount drunk on any day in the last week’).

Participants are asked about beers, cider, wine and other alcoholic drinks and the drink sizes that they drank. From HSE 2022, cider drinking has been asked about separately using the same format of questions as for beer, lager and stout which separates it into normal strength and strong categories. This information is converted into estimates of the units of alcohol consumed using conversion factors described in table A below. 

One unit of alcohol is 10ml by volume of pure alcohol (ABV). Table A below shows the current and revised conversion factors for converting what and how much of a beverage was drunk into units of alcohol. Based on the HSE Alcohol Working Group recommendations, increases in the unit conversion factors were applied to the following beverages:

• normal strength beer, lager, stout, cider, shandy (pints and large cans)
• strong beer, lager, stout, cider (large cans)
• wine (bottles, small, medium, and large glasses). 
• Conversion factors for other beverage sizes remained unchanged

Table A: Conversion factors for estimating alcohol content of drinks 

Published estimates of alcohol consumption in HSE 2019 and HSE 2021 were compared with estimates using the revised alcohol conversion factors to assess the effect of using the new conversion factors. See the Alcohol consumption methodology changes to alcohol unit conversion factors. 

The revisions to the alcohol unit conversion factors resulted in higher alcohol consumption estimates. This is because conversion factors were revised upwards for some drinks and no change was applied to other drinks, resulting in estimates of higher alcohol consumption for men, women and across all age groups. The estimate of the average (mean) alcohol units consumed increased. 

The revision had a larger impact on alcohol consumption estimates for men than women, reflecting that men often have higher alcohol consumption than women and probably also reflecting differences in the types of drinks consumed as men drink more beer than women do. 

There is some variation across age groups in the size of the increase in the estimate of consumption, although the general patterns of alcohol consumption across age and sex groups were broadly similar when using current or revised estimates.

The revision to conversion factors had a larger effect on estimates derived from data relating to the maximum amount of alcohol consumed on any day in the previous week than estimates derived from data relating to drinking in a typical week. Larger increases were seen for men than for women and among older age groups on the measure of the proportion of adults drinking more than 3 units(women) and 4 units(men) on any day in the past week. 

The change in conversion factors affects assessment of yearly change in alcohol consumption. The revised conversion factors due to be implemented from HSE 2022 onwards will be clearly indicated in the trend tables with the estimates on both conversion factors (current and revised) presented next to each other in the trend tables. Footnotes will clearly reference the change and point to the HSE 2022 Methods report which will include details of the revision. 

Estimates in previous statistical publications will not be revised. 

Researchers using the HSE datasets who aim to assess changes over time before and after 2022 are advised to ensure that they use the same conversion factors across years. The HSE 2022 dataset will include both versions of the alcohol variables (using current and revised conversion factors).

For further information about the effect of using the revised conversion factors on the published estimates of alcohol consumption in HSE 2019 and HSE 2021. 

More information about the survey is available at Health Survey for England - Health, social care and lifestyles - NHS Digital