This is a secondary analysis of a nationally-representative population-based survey named “The Food and Nutrition Surveillance Survey” (VIANEV, acronym in Spanish) and conducted in the period of 2017–2018 .
Individuals aged 18 to 59 years, with a fasting period of at least 9 h but not more than 12 h were potentially eligible to participate. Pregnant women, adults taking a medication affecting glucose or lipid profile, those with gastrointestinal problems affecting usual diet, and those with a congenital condition or any problem preventing anthropometric assessment were excluded. For this assessment, records with complete data of second-hand smoking and hypertension and variables related to cardiovascular risk (i.e., systolic blood pressure, glucose, total cholesterol, etc.) were included.
This survey selected individuals using a multistage random sampling approach and has been reported elsewhere . Briefly, three different strata were used: urban, rural, and Metropolitan Lima/Callao. Clusters were selected using a random systematic procedure with a probability proportional to the adult population size, totaling 621 clusters (176 in Lima, 260 in urban settings, and 185 in rural areas), with the selection of six households in Lima and urban settings, and eight households in rural areas. Further, households were selected whether they have at least an individual in the proposed age range, and using a random and systematic technique. Eligible participants were invited to participate and an informed consent was applied. If a subject rejected participation, a replacement was selected using a random approach.
Definition of variables
Outcome Two were the outcomes of interest. The first one was hypertension status, defined according to the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7) . Thus, a subject with hypertension had a systolic blood pressure (SBP) ≥ 140 mmHg, or a diastolic blood pressure (DBP) ≥ 90 mmHg, or reported having previous physician diagnosis of high blood pressure levels.
The second outcome was cardiovascular risk, evaluated using the Framingham 10-year cardiovascular disease event risk prediction  and the World Health Organization (WHO) 10-year risk of cardiovascular disease (CVD) . The decision to use two different cardiovascular risk scores was based on the poor concordance between current risk scores showing the uncertainty of selecting any of them for public health and clinical interventions in Peru . The Framingham score utilizes the sex, age (in years), systolic blood pressure (mmHg), use of anti-hypertensive medication, smoking status, diabetes status, high-density lipoprotein level (mg/dL), and total cholesterol (mg/dL). On the other hand, the WHO risk score used data from the Emerging Risk Factors Collaboration and recalibrates the predicted risk scores to reflect the expected 10-year risk in contemporary populations in 21 global regions, using the sex, age (in years), smoking status, history of diabetes, systolic blood pressure (mmHg), total cholesterol (mmol/L), and body mass index (kg/m2). Both risk scores were included as a percentage numerical value for analysis.
Exposure Second-hand smoking was the exposure in this analysis, and defined if the subject reported passive smoking at home or at work . This assessment was based on the same questions as a previous worldwide report : “During the last 7 days, on how many days did a member of your household smoke in your presence?” and “During the past 7 days, on how many days did someone smoke indoors at work (office, building) and in your presence? For descriptive purposes, both variables were analyzed separately; but, for main analysis, both were combined and total second-hand smoking was considered whether the participant reported to be exposed to passive smoking for at least 1 day . Unfortunately, data about degree or duration of exposure were not collected in the survey, and for instance, was not available for analyses.
Co-variables Other variables were utilized in the analysis as potential confounders. Sociodemographic variables included sex (female vs. male), age (< 30, 30–39, 40–49, and 50–59 years), education level (< 7 years, 7–11 years, and 12 + years), and socioeconomic position, built based on household assets, and split into tertiles (low, middle, and high). In addition, behavioral variables were also added, including current smoking (no current smoking, current smoking, and daily smoking), alcohol drinking (no in the last 12 months, in the last 12 months but not in the last 30 days, and in the last 30 days), and physical activity, using the short version of the International Physical Activity Questionnaire (moderate/high vs. low levels).
STATA 16 for Windows (StataCorp, College Station, TX, US) was used for analysis. All the analysis were performed using appropriate statistical techniques for complex sample and subpopulation analyses . An initial description of the study population was conducted using mean and standard deviation (SD) for numerical variables, and frequencies and proportions for categorical ones.
Prevalence and 95% confidence intervals (95% CI) were pursued for our exposure and hypertension outcome, whereas mean and 95% CI was used for estimating overall 10-year cardiovascular risk. Comparisons were conducted using the Rao-Scott Chi-squared test for categorical variables, and the F-test for numerical ones.
To assess the association between second-hand smoking and hypertension, crude and adjusted Poisson regression models were used, reporting prevalence ratios (PR) and 95% CI. On the other hand, crude and adjusted linear regression models were utilized to assess the association between second-hand smoking and 10-year cardiovascular risk, reporting coefficients and 95% CI.