Association between sleep difficulties as well as duration and hypertension: is BMI a mediator?

Abstract

Sleep difficulties and short sleep duration have been associated with hypertension. Though body mass index (BMI) may be a mediator variable, the mediation effect has not been defined. We aimed to assess the association between sleep duration and sleep difficulties with hypertension, to determine if BMI is a mediator variable, and to quantify the mediation effect. We conducted a mediation analysis and calculated prevalence ratios with 95% confidence intervals. The exposure variables were sleep duration and sleep difficulties, and the outcome was hypertension. Sleep difficulties were statistically significantly associated with a 43% higher prevalence of hypertension in multivariable analyses; results were not statistically significant for sleep duration. In these analyses, and in sex-specific subgroup analyses, we found no strong evidence that BMI mediated the association between sleep indices and risk of hypertension. Our findings suggest that BMI does not appear to mediate the association between sleep patterns and hypertension. These results highlight the need to further study the mechanisms underlying the relationship between sleep patterns and cardiovascular risk factors.

Keywords: Body mass index; hypertension; obesity; sleep apnea; sleep disorders.

Figure 1

Diagram for the mediation analysis. Baron and Kenny defined a set of models that must be met to define a mediator variable [26]: (i) there is a significant association between the exposure and the outcome (path A); (ii) there is a significant association between the exposure and the mediator (path B); (iii) including the exposure and mediator in the model, there is a reduction of the association estimate between the exposure and outcome (estimates in path D < path A). These requisites for paths A, B, and D should be met to consider a variable to be a mediator.