Main results
We found that lifetime smoking prevalence was higher in urban dwellers, intermediate in migrants, and lower in rural dwellers. This indicates that following on a process of internal migration, subjects are more exposed to smoking behaviors than rural dwellers, and experience more smoking. However, smoking incidence was not different between rural and migrant groups. In comparison, prevalence and incidence of heavy drinking were similar between rural, migrant and, urban groups.
Smoking patterns
When comparing four “current smoking” definitions, it is clear that prevalence found with definitions that asked for “occasionally or daily smoking” tend to be higher than the prevalence found with definitions that asked for “smoking in the last month”. Moreover, these differences seem to be higher among rural dwellers, suggesting that more objective definitions of current smoking are needed, especially in low-consumption settings.
In addition, in definitions 1 and 2, which did not utilize the 100 cigarettes threshold, no trend was observed. Implying, perhaps, that secular changes are occurring, and rural dwellers have recently started smoking; thus, they endorsed smoking in the last month but denied smoked more than 100 cigarettes in their lifetime. Although not statistically significant, this seems to be reinforced by the higher, smoking incidence in the rural group.
Our population has a low smoking prevalence, consistently with previous studies conducted in Peru [32, 33]. Conversely, prevalence of daily smoking in high income countries reaches 13.7% in United States [34] and 25% in Finland [35]. Among daily smokers, the mean of cigarettes per day consumed by our population was under five cigarettes per day, lower than in other Latin American cities as Santiago (Chile), Quito (Ecuador), Bogota (Colombia), and Mexico City [33], and other countries as United States [26] and China [36].
Smoking prevalence and incidence rates were lower in migrants than in the urban population, which suggest that the rural background have a protective effect. Lifetime smoking was significantly higher in the migrant than in the rural group. This smoking pattern is similar to that found with Chinese rural-to-urban migrants [4], where behavior habit adoption has been attributed to acculturation, stress [11] and poor mental health [37]. Conversely, in the adjusted analysis, PMH, a mental health status evaluation, was not associated with smoking prevalence or incidence. However, since our migrant group lived in an urban environment for an average of 32 years, it is possible we are not observing an association of PMH that is given only among more recent migrants. On the other hand, current smoking was not significantly different among rural and migrant groups, possibly due to the low prevalence of current smokers and the small sample size.
Smoking prevalence rates followed a consistent trend in our population (urban > migrant > rural). We found four studies that also compared smoking prevalence rates between the rural-to-urban migrants, urban, and rural groups. A study in Yi migrants (China) found the same trend but only in men, while smoking prevalence among women was higher in the migrant group than in the rural and urban groups [6]. A multi-country study found that migrants had a higher ever smoking prevalence than rural dwellers in Mexico, while no significant difference was found in China, Ghana, India, Russia, and South Africa [17]. These mixed results may be explained by differences in time since migration, smoking patterns, or the acculturation process between population groups included in those studies and ours. In addition, studies in India [9] and China [16] found that male migrants had lower cigarette consumption than rural and urban males. In these last studies, the migrant group was composed of workers, so it is possible that selective migration of people with the best education and predisposition to improve their lifestyle would explain their low consumption, while migration in our study was influenced by political violence lived in Ayacucho [38, 39] which could have reduced this selective migration effect.
From the longitudinal point of view, only two prospective studies evaluating smoking in rural-to-urban migrants were found. A study in Tanzania [5] compared current smoking rates before migration and one to three months after migration, and found a non-significant increase in smoking rates (from 16.2 to 23.5%) only in men, while no women reported smoking in either evaluation. Another study in Indonesia [18] followed-up recent migrants, approximately 65% migrating less than three years ago, and found no significant increase in smoking initiation, but a clear increase in the number of daily cigarettes smoked. These studies suggest a slight increase in smoking rates after migration, but give no information about risk in long-term settled migrants.
While lifetime smoking prevalence was higher in migrants than in the rural population, smoking incidence was not significantly different between those populations. This may suggest that the risk of initiating smoking in migrants could increase during the first years post-migration, and later decrease over time. To evaluate this assumption, we made a post-hoc analysis in our migrant group, and found that prevalence rates of having smoked in the last month were 0.0, 14.9, and 11.3% among those who migrated <15, 15 to 30, and >30 years prior to the baseline assessment (Fisher’s exact p = 0.244). Accordingly, incidence rates were 0.0, 3.5, and 1.3% in these sub-groups (Fisher’s exact p = 0.334). These findings suggest a higher smoking risk at 15 to 30 years of migration.
Heavy drinking
The prevalence of heavy drinking in the last year was similar between the urban, migrant, and rural groups. Accordingly, studies that evaluated alcohol intake in Guatemala [14] and alcohol dependence in Canada [40], found similar patterns between rural-to-urban migrant and rural groups. However, data from Tanzania [5] found that weekly alcohol consumption prevalence increased after migration, and studies assessing monthly drinking in Vietnam [7] and alcohol intoxication in China [15] found that rural-to-urban migrants had higher rates than the urban population.
Three previous studies have compared alcohol intake rates between the rural-to-urban migrants, urban, and rural groups. One of them [6] made in Yi migrants (China), found that migrants had similar prevalence rates of current alcohol use than rural and urban dwellers. The other study, also in China [16], surveyed migrants recruited in workplaces and reported that they had higher alcohol intoxication rates than rural and urban dwellers. While the first study resembles our results, the second did not, possibly because their participants were workers, younger (mean age 25 years), and therefore possibly more prone to alcohol drinking, than our migrant group with mean age of 48 years. The third study found similar alcohol use between rural and migrant groups in Ghana, India, Mexico, Russia, and South Africa, while migrants had lower alcohol use than rural dwellers in China [17].
We only found one longitudinal study that evaluated alcohol intake in rural-to-urban migrants in Tanzania, which found that weekly alcohol consumption has a non significant increase after migration [5]. In our longitudinal analysis, incidences of heavy drinking were similar between the three study groups. As for smoking, we verified whether heavy drinking increases after the first years of migration in post-hoc analysis in our migrant group, and found that prevalence rates of heavy drinking were 18.2, 7.1, and 8.6% among those who migrated <15, 15 to 30, and >30 years previous to baseline assessment (Fisher’s exact p = 0.270). However, incidence rates were 0.0, 3.9, and 0.8 in these sub-groups (Fisher’s exact p = 0.099). These findings, along with the Tanzania study, are consistent with a non-significant increase in heavy drinking in the first years after migration.
Subjects in our rural and urban settings, although living in different socio-environmental contexts, had similar heavy drinking rates. This may reflect similar heavy drinking manners in our urban and rural populations, along with similar alcohol access besides economic differences, probably because low resource individuals in our settings can purchase low-cost artisanal alcoholic drinks [30]. Some studies suggest that recent migrants may present migration-related psychological distress, which was associated to higher alcohol consumption [41, 42]. However, PMH, a mental health status evaluation, was not associated to heavy drinking in late-term migrants.
Classically, smoking has been associated with alcohol intake and with heavy drinking [43, 44]. However, in Peru, alcohol intake prevalence is much higher than smoking prevalence [45], and our results show that increasing smoking rates in migrants are not accompanied by an increase in heavy drinking rates. A possible explanation is that low-resource populations do not have enough money to buy cigarettes, but they can manufacture low-cost artisanal alcohol drinks [30]. Accordingly, asset index was associated with the prevalence of lifetime smoking, but not with the prevalence of heavy drinking.
Public health relevance
Our results present smoking and heavy drinking patterns in a rural-to-urban internal migration in Peru, which may be similar to other rural-to-urban internal migrations in Peru and other developing countries.
Our results indicate that migrants are at risk to increase their smoking patterns, especially in the first years after migration. Thus, smoking interventions in migrant populations appear more beneficial if oriented to prevent smoking initiation rather than cessation. These observations are not against major tobacco control policies that remain to be sustained as beneficial public health policies at the country-level [46].
Post-hoc analyses show not significant lower smoking rates and higher heavy alcohol drinking rates among those who migrated in the past 15 years. Future studies in recent migrants could identify which would be the best moment for preventive interventions in smoking and alcohol consumption.
It is also important to take into account that Peruvian rural settings could have a higher use of artisanal alcohol distilled drinks with high alcohol concentration [30], which may have a higher concentration of aliphatic alcohol [47], and therefore represent an additional risk of liver damage [48].
Strengths and limitations
This study has assessed smoking and heavy drinking in well-defined rural, urban, and migrant populations. This allows a better understanding of the influence of rural–urban migration in the consumption patterns, and can be used to improve health interventions targeted towards these migrants.
However, some limitations deserve consideration. First, all the variables studied were self-reported, with the inherent social desirability bias. Nevertheless, previous studies in other countries reinforce use of self-reporting as a reliable method to measure the smoking status [49–51] and alcohol consumption [52, 53] in the general population. Second, there are some confounders that we could not address, such as smoking/drinking status before migration, or reason of migration. Finally, some studies have reported that female migrants may be at higher risk of cigarette [54, 55] and alcohol consumption [56] compared to males. However, since we did not have enough cases to stratify by sex, we could not explore this.
In addition, we have to highlight that the smoking status categorization we used in this study is primarily driven by frequency of consumption (having consumed cigarettes in the last month), without considering the amount component (how many cigarettes have been smoked). Thus, in our population, in which the number of cigarettes consumed is low, current smokers will have a lower smoking-related risk than current smokers in other countries with high smoking prevalence [57]. Also, our results suggest an overestimation of current smoking rates among rural dwellers when using definitions based on “occasionally/daily smoking”. Thus, studies using this definition may find different smoking rates and different measures of association than those found in our study.