- Published: August 12, 2015
- DOI: 10.1371/journal.pone.0135660
The relationships between alcohol consumption and sexual behaviour are complex, with empirical support for causal relationships in both directions, and for shared causes of both behaviours, depending on the context and population [1–3]. Apart from selected high risk populations such as those infected with HIV , most published research has focused on adolescents and young adults. Among young people, the high prevalence of hazardous alcohol consumption, risk-taking, and sensation-seeking activities has made it difficult to quantify the causal elements of commonly observed associations between alcohol and sexual outcomes [15 6]. However, there is substantial evidence for the cognitive effects of alcohol affecting decision-making and resulting in riskier choices regarding sexual activity [1 6–8], and a recent systematic review concluded that blood alcohol concentration is an independent risk factor for the intention to engage in unprotected sex among young adults (mean age 24.0 years) in North American college and community settings .
In general populations, the prevalence of hazardous alcohol consumption is typically lower in older age groups , along with lower levels of other risk-taking behaviours, and in concert with the formation of long term sexual partnerships. However, cross-sectional surveys do not separate age and cohort effects on alcohol consumption, and changes in the last two decades suggest that alcohol’s role in sexual behaviour beyond young adulthood may have become more relevant to sexual health outcomes.
Adults currently in their late thirties in most English-speaking countries have been exposed to a youth culture where hazardous drinking behaviour has been common from early teenage years  and where, at least in the UK, first sexual intercourse is more likely to have been experienced when intoxicated than previously . Young women’s drinking has increased sharply in a single generation , and gender convergence of drinking patterns is commonly seen [11 14], with increased drinking among women of all ages during the last two decades .
Breakdown of long term relationships, and initiation of new ones, are not uncommon in the 30–40 year age group and there are a number of roles alcohol use might play in these transitions, particularly if there has been a persistence of, or return to, drinking behaviour experienced as a young adult . Among the potential adverse consequences of heavy drinking for sexual health in this age group are those already identified in younger people, such as sexually transmitted infections, unwanted pregnancies, and regretted sexual experiences .
Little has been published in the last twenty years describing alcohol use in the context of sexual behaviour of heterosexual adults over 30 in the general population, or quantifying associations of their alcohol use with sexual behaviour and/or health. Most studies have been conducted in non-representative groups such as military personnel , men who have sex with men, or STI clinic attenders . One exception is a 1994 population-based cross-sectional study in the U.S. which analysed several drinking measures in relation to being sexually active, having more than one partner in the past year, and condom use . However, no age- or sex-specific findings were reported. Another is the Natsal-2 study in the UK, which compared nationally representative surveys of 16–44 year olds in 2000/1 and 1990/1 with respect to alcohol use at first heterosexual intercourse, and quantified the association of heavier drinking (defined as an average level above current guidelines) with a range of outcomes: numbers of sexual partners, unprotected sex, prevalence of sexually transmitted infections (STIs), sexual function problems, terminations of pregnancy (TOPs) and emergency contraception use . However, this study published age-adjusted rather than age-specific findings, and did not investigate the association of frequency of heavy drinking episodes with sexual risk behaviours or outcomes, even though the implicit mechanism of effect is intoxication.
In this paper we report on alcohol’s role in sexual behaviour and outcomes among 38 year olds from a New Zealand birth cohort. In particular we describe, for men and women separately, 1. self-reported use of alcohol in relation to sexual activity and perceived consequences of that use, 2. cross-sectional associations of heavy drinking frequency with self-reported alcohol involvement in sex, 3. associations of heavy drinking frequency with partner numbers, STIs and TOPs, and 4. whether associations of heavy drinking with these three outcomes have changed since the 26–32 year old period of the same cohort.
Members of the Dunedin Study birth cohort answered computer-presented questions about sexual behaviour and outcomes, and interviewer-administered alcohol consumption questions, at age 26, 32 and 38 years.
Response level was >90% at each assessment. At 38, drinking before or during sex in the previous year was common (8.2% of men; 14.6% of women reported “usually/always”), and unwanted consequences were reported by 13.5% of men and 11.9% of women, including regretted sex or failure to use contraception or condoms. Frequent heavy drinkers were more likely to “use alcohol to make it easier to have sex” and regret partner choice, particularly women. Heavy drinking frequency was strongly associated with partner numbers for men and women at 32, but only for women at 38. Significantly higher odds of STIs amongst the heaviest drinking men, and TOPs amongst the heaviest drinking women were seen at 32–38.
Alcohol involvement in sex continues beyond young adulthood where it has been well documented, and is common at 38. Women appear to be more affected than men, and heavy drinking is associated with poorer outcomes for both. Improving sexual health and wellbeing throughout the life course needs to take account of the role of alcohol in sexual behaviour.
For full paper visit: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0135660