The associations between alcohol intake and cardiometabolic risk in African-origin adults spanning the epidemiologic transition

Cardiometabolic (CM) risk affects approximately 25% of adults globally [1, 2]. The National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults defines diagnosis as having any three of the following five CM risk factors: elevated blood pressure, high triglycerides (TG), elevated blood sugar, low high-density lipoprotein (HDL) level and abdominal obesity [3‐5]. It is estimated that mortality rates are approximately 22% higher for adults with high CM risk compared to healthy adults [6]. While several non-modifiable risk factors, including age and sex have been determined to increase CM risk; the contribution of alcohol consumption remains inconsistent [7‐10]. For example, many studies have demonstrated that the amount of alcohol intake is associated with individual CM risk factors; including hypertension, hypertriglyceridemia and hyperglycemia [7‐9, 11, 12]. The level of alcohol consumption may show either increased or decreased risk for the individual CM factors, [13‐17]. Despite these independent associations, data are lacking showing a causal link between alcohol consumption and overall CM risk. Given the international prevalence of alcohol consumption, with some countries reporting 80% of the population drinking regularly, and the global burden of high CM risk, this potential association warrants additional examination [1, 2, 18‐20].

Recently, a meta-analysis from the Global Burden of Disease Study group examined 694 studies from 195 countries between 1990 and 2016, and found that alcohol consumption significantly increased CM risk [10]. This contradicts previous studies, which found that low levels of alcohol consumption may be protective against CM risk [21, 22]. For example, Freiberg et al. [22], reported that adults who regularly drink small amounts of alcohol have 40% lower odds for increased CM risk than adults who do not consume alcohol. However, this effect was less significant in African American participants than in white participants. The contradictory findings between these two studies suggests that any proposed associations have not yet been confirmed.

Previous studies have shown genetic/phenotypic relationships between country of origin and CM health. Factors such as abdominal obesity, HDL-cholesterol and other measures of CM health vary greatly due to differences in dietary and behavioral behaviors among countries [23, 24]. For example, a study that examined CM risk in 195 countries showed that the prevalence of high CM risk is higher in developing urban communities than in rural or fully developed areas, suggesting an epidemiologic effect on CM risk [23]. This may be as a result, in part, due to a higher caloric intake and other behavioral factors associated with urban populations as well as a higher prevalence of obesity in the latter than the former. A study examining rural and urban populations from 200 countries found obesity to be associated directly and fairly strongly with higher HDL-cholesterol, triglycerides and blood sugar levels [25].

Some studies have examined CM risk in African-origin populations living in Africa. However, to our knowledge, no previous studies have examined the relationship between alcohol consumption and CM risk have included African-origin participants living in Africa. Previous studies have already shown that different populations are not similarly affected by the separate factors, and that each population may respond to alcohol consumption differently [13‐15, 26]. Therefore, the aim of this investigation was to examine the association between alcohol consumption and elevated CM risk in adults of African-origin using data from the Modeling the Epidemiologic Transition study (METS) [13, 14].

METS is a prospective cohort study examining physical activity and weight change in 5 African-origin cohorts from Ghana, Jamaica, South Africa, Seychelles, and the United States of America (USA) (N = 500 at each site). METS was initiated in 2009. In total, 2506 participants of African origin, aged 25–45 years were recruited. Approximately 50% of participants were women (N = 1339), and all participants self-identified as African-origin. Sites were categorized using the 2010 United Nations’ Human Development Index (HDI) [15]. In 2010, Ghana was ranked as low HDI (0.554), South Africa was ranked as moderate (0.645), Seychelles and Jamaica were ranked as high (0.747 and 0.712, respectively), and the USA was ranked as very high (0.914). Data for the current study were collected during the baseline clinic visit, between the months of January 2009 and December 2011. The protocol for METS was approved by the Institutional Review Board of Loyola University Chicago, IL, USA (LU#200038); the Committee on Human Research Publication and Ethics of Kwame Nkrumah University of Science and Technology, Kumasi, Ghana; the Research Ethics Committee of the University of Cape Town, South Africa; the Board for Ethics and Clinical Research of the University of Lausanne, Switzerland; the Research and Ethics Committee, Ministry of Health and Social Development, Seychelles Public Health Department, Republic of Seychelles, and the Ethics Committee of the University of the West Indies, Kingston, Jamaica. A written informed consent was obtained from all participants before enrollment.

Study inclusion criteria included participants who self-identified as African-origin and considered themselves healthy. Participants with obvious infectious disease, HIV positive individuals, women who were either lactating or pregnant, and participants unable to engage in normal physical activity were not eligible for the study due to the impact these conditions had on CM risk.

METS participants presented annually for a health check, which included CM risk measurements, and self-reported alcohol consumption. Two alcohol consumption metrics were used to estimate drinking behavior: the number of drinks per day and the frequency of drinking. The clinical measurements were used to estimate the prevalence of CM risk at each of the five sites.

We evaluated the association between alcohol consumption and elevated CM risk in five African-origin populations spanning the epidemiologic transition. The study found that among the groups, heavy alcohol consumption tended to be associated with an increased odds for presenting with elevated CM risk. It was observed that within sites, drinking status was associated with the various components of CM risk, including elevated BP, high triglycerides and low HDL. These associations varied greatly across each of the five sites, suggesting an effect of environmental factors on CM risk. These relationships also varied when stratified by sex indicating that sex may modify the association between alcohol consumption and CM risk.

We did, however, find that the association between alcohol consumption and increased CM risk is not consistent. For example, Freiberg et al. found that moderate alcohol consumption was significantly with a decreased risk for elevated CM risk [22]. This is in contrast to a recent meta-analysis from the Global Burden of Disease Study group, which suggested that alcohol consumption significantly increased CM risk [10]. Each of these studies, regardless of findings, demonstrated a dose-response effect, in which increased alcohol consumption resulted in either the protective or increased risk for the five CM risk factors [10, 21, 22, 31, 32]. While our study found no significant association between any amount of alcohol consumption and having increased CM risk, the data suggest a trend between heavy alcohol consumption and risk for CM among the men. This association was however, negated among the women as well as for the site-specific analyses, except among Ghanaian light drinkers who had a significant odds for having elevated CM risk. It is important to note that the lack of a significant association between heavy drinking and elevated CM risk in Ghana may be due to the small number of heavy drinkers, as only eighteen Ghanaian men and twelve Ghanaian women qualified as heavy drinkers.

While previous studies have not investigated the association between alcohol consumption and high CM risk specifically among African-origin populations, several studies have explored the prevalence of high CM risk in each of our five cohorts. For example, the prevalence of high CM risk in Ghana was found to be 5.9% in men and 24% in women in 2012 [33]. In South Africa, the prevalence was 10.5% in men and 25% in women in 2011 and 11% of men and 23% of women in Jamaica had high CM risk in 2008 [18]. In Seychelles, the prevalence was 24% in men and 32.2% in women in 2008 [27]; and among US-African Americans, 24% of men and 42% of women had the metabolic disorder in 2003. With the exception of Ghanaian men, these previous studies reported higher rates of high CM risk than this investigation. In some cases, the differences in prevalence exceeded 20%, as was the case for the USA and Seychelles.

However, our data, also, identified similar findings as previous studies. For example, we similarly identified higher prevalence of CM risk among Ghanaian women compared to Ghanaian men. Similarly, we identified a higher prevalence of low HDL among Ghanaian and South African women when compared to Ghanaian and South African men, respectively. Our data and previous data showed that prevalence of having an elevated CM risk increased with the site’s developmental index, i.e. lowest prevalence among Ghanaians and highest prevalence among the US cohort. Similar to previous literature, we confirmed that women had higher rates of elevated CM risk than men [18‐20, 34]. Similarities to previous research are limited as, to our knowledge, no other study has investigated the association between alcohol intake and CM risk in these populations.

Alcohol consumption has also previously been measured in each of the five cohorts. For example, previous studies have found that approximately 80% of Ghanaians were regular drinkers [34], 56% of men and 26% of women from South Africa admitted to drinking regularly [16] and in Jamaica 57% of men and 35% of women reported that they were regular drinkers [16]. In the Seychelles, approximately 51% of men and 6% of women were regular drinkers [17]; and about 75.5% of men and 63% of women reported to be drinking regularly in the USA [16]. These studies are not in line with our study, and may be partly due to the different classification of alcohol consumption, as well as differences in the methods and questions used to obtain self-reported data. Self-reported data generally introduce variation as the participants subjectively provide these data as opposed to objectively measuring alcohol consumption. Therefore, the methods used to obtain these self-reported data may introduce variation between studies. Despite these differences, we did find that more women were more likely to abstain from alcohol consumption compared to men in all sites.

One of the primary limitations of this study is that all alcohol data were self-reported, thus introducing biases, such as social desirability. Depending on the country of origin and social tolerance to alcohol drinking, some participants may under-report their alcohol consumption, and such systematic misclassification may be related to sex or different population sub-groups. Furthermore, alcohol habits may change over time, including low consumption or abstinence; following disease, itself possibly related to alcohol. However, this is not likely the case due to the relatively young ages of the study participants. Another limitation is that alcohol drinking patterns (e.g. binge vs. regular) and alcohol types (e.g. wine, beer, spirts, home-brews), which are factors that may alter the impact alcohol intake has on CM risk, were not captured. The prevalence of heavy drinking was relatively low in most of the sites, particularly in women, which minimizes statistical power for association analysis. In some instances, we were underpowered to detect statistical significance. For example, we were unable to test the association between heavy drinking status and risk for elevated blood glucose in Ghanaian women, as none of the heavy drinking female Ghanaians had hyperglycemia. Indeed, this site confounding may have masked some of the associations, although we attempted to address this by using dummy variables for site. Finally, it is a major limitation that we were unable to describe any potential mechanisms for the association between alcohol intake and prevalence of CM risk in our international cohort. However, our study is strengthened by the objective clinical measures, performed by certified staff, using standardized procedures and the same make of equipment across the five sites. Additionally, the biochemical samples were centrally stored and analyzed at the same laboratory.

While we were able to detect several statistically significant associations between individual CM risk factors and alcohol consumption, these associations were inconsistent. The associations between alcohol consumption and elevated CM risk and its components varied markedly between the 5 cohorts in this study. This is not unexpected, given the current widely reported alcohol consumption effects. Alcohol intake was indeed, inversely related to lower HDL and higher triglycerides in nearly all sites in our study. While cost-effective strategies to reduce alcohol consumption have been implemented, our data also underscore differences on health outcomes between countries, and the need to tailor national programs and policies accordingly. Future studies should focus on understanding the individual site-related effects.