Introduction

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Alcohol consumption increases the risk of various cancers, hypertension, liver disease, unintentional injuries, and violence. ^{1 2} Definitions of light and moderate alcohol consumption vary, but these levels of consumption are generally found to decrease the risk of ischaemic heart disease.^2-6 For all cause mortality the relation is typically U shaped, with non-drinkers and heavier drinkers having higher risks than light and moderate drinkers. ^{2 7-9} The royal colleges of physicians, psychiatrists, and general practitioners have therefore advised men and women to drink less than 21 and 14 units a week, respectively, whereas the UK government has recommended no more than 4 and 3 units a day, respectively; 1 unit is 8-10 g of alcohol. ^{10 11} However, the levels giving the lowest or a low risk are likely to vary with age as well as sex and have not been systematically quantified.¹² We used statistical models relating alcohol consumption to the risk of death from single causes to estimate the all cause risk for men and women of different ages in England and Wales.

	Methods

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Relative risks
Three reviews have quantitatively related alcohol consumption to comprehensive lists of causes of death. ^{1 13 14} The most appropriate review for our study was by Corrao and others because it included more recent studies, assessed study quality, and estimated risk as a function of alcohol consumption. ^{14 15}

Corrao and others described each cause specific risk by way of a linear, quadratic, or cubic function of alcohol consumption, or, for ischaemic heart disease, a model involving linear and square root terms. Where appropriate they excluded studies of lower quality. They reported results separately when significant differences were found between Mediterranean and non-Mediterranean countries, case-control and cohort studies, incident disease and death, or men and women: we used the results for non-Mediterranean countries, cohort studies, and deaths. Otherwise we used the pooled results. We expressed alcohol consumption in units a week, taking 1 unit as 9 g of alcohol.¹⁶ The risk functions for each cause of death by alcohol consumption are given on bmj.com.

Alcohol consumption
Alcohol consumption was reported by respondents aged 16 and over in the 1996-7 general household survey.¹⁷ We computed the proportions of men and women in England and Wales drinking 0 units of alcohol a week, drinking occasionally (taken as 0.25 units a week), drinking from 1 up to 100 in increments of 1 unit a week, and drinking more than 100 units a week, for age bands 16-24, 25-34, 35-44, and so on up to over 85.

Mortality
We obtained data on mortality for England and Wales in 1997 from the Office for National Statistics.¹⁸

View larger version (25K): [in this window] [in a new window]   Fig 1.   Risk of all cause mortality (relative to non-drinkers) by level of alcohol consumption in women and men

Pooling causes
We estimated absolute risk functions from the relative risk functions for each sex, age band, and cause by using the observed number of deaths and the distribution of alcohol consumption (see bmj.com). We summed the absolute cause specific risks to get all cause mortality for each sex and age band. The nadir is the level of alcohol consumption at which all cause risk is lowest.¹⁶

	Results

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Alcohol risk relations
Figure 1 shows the relation between all cause mortality and alcohol consumption, by age and sex. The absolute risks vary widely (table), so we show all risks relative to non-drinkers. For women there is a positive relation up to age 35-44, but the U shape appears from age 45-54. For men aged below 35 the curve is steeper than it is for women, but the U shape appears at age 35-44, and the reduction in mortality in the lightest drinkers is larger and is sustained up to higher levels of consumption than for women. Drinking at the royal colleges' recommended limit increases risk by 9% in women aged 16-24 and by 23% in men aged 16-24. For government limits these figures are 15% and 32%, respectively.

Estimated nadirs
Figure 2 and the table show the estimated nadirs. The nadir increases from 0 at ages 16-34 to around 3 units a week in women and around 8 units a week in men aged over 65. The 95% confidence intervals around the estimated nadirs are narrow, but they account only for uncertainty in the relative risks.¹⁹

View larger version (25K): [in this window] [in a new window]   Fig 2.   Level of alcohol consumption at which mortality is least (nadir) and level at which risk is raised by 5% above this minimum risk in women and men (95% confidence intervals show uncertainty due to relative risk functions only)

The 5% bounds are the levels of alcohol consumption at which risk is no more than 5% greater than the risk at the nadir. For women the 5% bound increases from 8 units a week at ages 16-24 to around 20 units a week over age 85. For men it increases from only 5 units a week at ages 16-24 (reflecting the steeper slope of the risk curve in young men compared with young women) to 30-35 units a week over age 65.

Sensitivity analyses
An alternative risk function for ischaemic heart disease lowers the nadirs, for example from 8 to 5 units a week in men aged over 65. An alternative way of splitting deaths from stroke lowers the nadir for men aged over 75. Assuming ischaemic stroke to be unrelated to alcohol consumption slightly increases the nadirs, whereas assuming breast cancer to be unrelated to alcohol consumption has no appreciable effect.

	Discussion

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If our results are not subject to bias or confounding (see bmj.com) and if the effects of alcohol consumption act over no more than 5-10 years, then the average person can decrease his or her risk of mortality by drinking at a level nearer the nadir.

Possible evidence based guidelines for sensible drinking can be derived from figure 2 and the table if no more than a 5% increase in risk of mortality is considered acceptable. Women would be advised to limit their drinking to 1 unit a day up to age 44, 2 units a day up to age 74, and 3 units a day over age 75. Non-drinking men aged 55-84 have a risk slightly more than 5% above the minimum risk, but we would not encourage these men to drink, because this might increase the overall public health burden of heavier drinking. Men would be advised to limit their drinking to 1 unit a day up to age 34, 2 units a day up to age 44, 3 units a day up to age 54, 4 units a day up to age 84, and 5 units a day over age 85. These levels are similar to current limits at older ages but considerably lower at younger ages.

Alternatively, the 9-32% increase in risk for younger people at the current limits of sensible drinking might be considered acceptable because it implies a smaller absolute increase than the same percentage at older ages, even allowing for additional years of life lost through deaths at a younger age. Public health must also take account of morbidity and social harm, which are harder to measure than mortality but much more adversely affected by alcohol consumption.²⁰ Finally, as most deaths attributable to alcohol at younger ages are due to injuries, a greater focus could be placed on avoiding risky patterns of drinking rather than on reducing average alcohol consumption. ^{21 22}

	Acknowledgments

We thank Gianni Corrao and Vincenzo Bagnardi for helpful discussions and for analysing their data further for us and Annie Britton for helpful discussions.

Contributors: See bmj.com

	Footnotes

Funding: Alcohol Education and Research Council (grant No R17/97).

Competing interests: None declared.

The full version of this article appears on bmj.com

	References

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(Accepted 12 February 2002)