This is the first attempt to synthesise and harmonise information on alcohol consumption from overlapping cohorts to represent the whole life course, using data from large population based cohorts of men and women, with multiple repeated measures of consumption as they age. Our analyses describing the average volume of alcohol consumed showed a rapid increase in consumption during adolescence, followed by a plateau in mid-life, and then a decline into older ages. Drinking occasions, on the other hand, tended to become more frequent with daily/nearly daily consumption being most common in older men, suggesting a shift away from irregular drinking in earlier years. This latter finding supports concerns raised recently about the misuse of alcohol among older people [48].

The trajectories are based on over 174,000 alcohol observations. With a minimum of three repeated measurements from each cohort, we were able to model non-linear effects. This was a serious limitation of previous work [30,31]. Great care was taken to harmonise the information on volume and frequency despite it being gathered using different questionnaires; however, we were not able with these datasets to capture full details of drinking pattern or context of drinking occasions over time. The volume and frequency estimates were reliant upon self-report, which may lead to both over- and under-estimation [49] and the strength of some alcohol consumed is likely to have increased over time [12]. Estimates of population level alcohol consumption from surveys are lower than sales data suggest, largely due to their failure to capture heavy drinking sections of society [50,51]. Furthermore, longitudinal population cohort studies are at risk of selective attrition, which may mean that heavier drinkers were more likely to drop out [52]. However, our sensitivity analyses showed that selective attrition did not seem to affect the main results.

Our findings are broadly in agreement with individual studies on drinking behaviour change which report that alcohol consumption decreases with age [13,14,24,30], with some suggesting that drinking patterns stabilise around the age of 30 [31] and in middle age [29], whilst others suggest later at age 50 years [25]. Fillmore et al. [30] combined data from 20 longitudinal studies from Europe, US, and New Zealand to look at changes in quantity of drinking and found that mean consumption declined significantly with age in men until they reached their seventies, whilst mean consumption in women decreased slightly at ages 15 to 29 and 40 to 49 years [30]. In an updated meta-analysis of these studies, Johnstone et al. [31] evaluated drinking frequency and found settled patterns after the age of 30 years following earlier marked variation. In these meta-analyses, change in consumption was assessed using only two measurements of alcohol and, therefore, the authors were unable to estimate trajectories of change with growth curve or other dynamic modelling procedures.

The data presented in this paper were collected over a 34 year period (1979 to 2013) and the participants were born in different eras (spanning 1918 to 1973), therefore, the interpretation needs to be set against period and cohort effects [53]. To a certain extent, we were able to look at period effects by examining data collected in three different decades and found only minor differences. Furthermore, this is corroborated with data from the World Health Organisation, which suggest there have been only minor differences in the estimates of alcohol per capita over the last two decades [54]. On the other hand, the overlapping cohorts provide an opportunity to compare the robustness and time-resistant nature of the trajectories. Clearly, there are some cohort differences, which are likely to be partly attributable to covariates such as socio-economic position. The lower estimates of male alcohol consumption in the Whitehall II cohort are likely due to it being a ‘white collar’ occupational cohort compared to the other population-based cohorts. We chose not to adjust for covariates, but to present the actual trajectories for each cohort separately and combined.

Reassuringly, the estimates from the nine UK cohorts of around 15 to 20 units per week for adult men are similar to the estimates obtained in the General Lifestyle Survey (GLS), which covers Great Britain (mean of 17.8 units for men aged 45 to 64 years, 2010) [55]. The female cohort estimates of 4 to 6 units are slightly lower than the GLS estimates (approximately 8 units per week across adulthood). The GLS data also suggests declines in older age groups with lower average consumption among people aged 65 and over (12.5 units for men and 4.6 for women). However, the GLS cross-sectional data is fixed at one point in time (2010 in the case here) and should not be used alone to describe age-related alcohol trajectories.

In this paper, we focused on mean trajectories of consumption, which, by necessity, masks the individual variations. Future work will classify trajectories of lifetime drinking according to profiles (for example, persistent heavy drinker, increasing drinker, sporadic drinker, etc.) using growth mixture modelling or latent class analysis [19,56,57] and, where available, the identified trajectory profiles will be analysed in relation to outcome data such as mortality and incidence of cardiovascular disease and cancer. This will allow for the investigation of whether there are sensitive periods during life when certain patterns of alcohol consumption are more harmful and whether the impact of drinking accumulates over time [58]. Such information can be used to inform public health initiatives and sensible drinking advice.

Capturing variations in drinking pattern over time has been the focus of scientific endeavour for decades [13] and it has long been known that alcohol consumption may fluctuate over the life course. However, much of the evidence linking alcohol to health outcomes relies upon evidence from prospective cohort studies in which exposure to alcohol is measured only once at baseline. It is assumed that this initial consumption level is an accurate measure of exposure throughout the study period (which may be several decades for some health outcomes). Epidemiological studies using just one exposure measure of alcohol, as is typically done, should be treated with caution. The current evidence base lacks this consideration of the complexity of lifetime consumption patterns, as well as the major predictors of change in drinking and the subsequent health risks. Research on the health consequences of alcohol needs to address the effects of changes in drinking behaviour over the life course [59].