The relationship between physical activity and sleep among pregnant women

Abstract

Statement of problem

Few studies have examined the influence of physical activity on sleep among pregnant women. To examine the potential sleep-enhancing benefits of physical activity among pregnant women and to therefore see if physical activity may serve as a non-pharmacological treatment for sleep disturbances during pregnancy, this study’s purpose was to examine the association between objectively-measured physical activity and sleep among a nationally representative sample of U.S. pregnant women.

Methods

Data from the National Health and Examination Survey 2005–2006 was used for the present study. 138 pregnant women who had worn an ActiGraph 7164 accelerometer on the right hip for at least 4 days for a minimum of 10 h per day were identified. Questions on sleep were asked during the household interview.

Results

Of the 22 sleeping-related parameters assessed, physical activity was only associated with two. After controlling for depression, gestation, income and parity, for every 1-min increase in moderate-to-vigorous physical activity, pregnant women were 17% less likely to have difficulty finishing a meal because of being tired or sleepy (OR = 1.17, 95% CI: 0.98–1.38, p = 0.06).

Conclusion

Our data suggests a weak relationship between objectively-measured physical activity and sleep. Additional research using a larger sample of pregnant women, as well as experimental studies, are needed to determine the extent to which physical activity may assist in improving sleeping-related parameters among pregnant women.

Introduction

Although exercising during pregnancy was once thought to be deleterious to the fetus through hypothetical risks such as acute fetal hypoxia and hyperthermia (Wolfe et al., 1989), empirical evidence suggests otherwise during uncomplicated pregnancies (Zeanah & Schlosser, 1993). For example, Brenner, Wolfe, Monga, and McGrath (1999) showed that a brief progressive exercise test terminated at a maternal heart rate of 170 beats per min did not induce fetal distress during a healthy pregnancy. With respect to maternal health, Lotgering, Spinnewijn, Struijk, Boomsma, and Wallenburg (1998) evaluated respiratory and metabolic responses to endurance cycling exercises among pregnant and postpartum women and showed that pregnant women were equally capable as postpartum women to safely perform approximately 40 min of cycling at 70–75% VO₂ peak.

Furthermore, appropriate levels of exercise during pregnancy can result in positive health outcomes for the mother and the baby (Artal and O’Toole, 2003, Ji and Han, 2010, SMA, 2002). Maternal benefits to exercise include both physical and psychological changes, such as reduced fatigue and swelling of the lower extremities (Wallace, Boyer, Dan, & Holm, 1986), and less insomnia, stress, anxiety, and depression (Clapp et al., 1992). Although limited, there is some evidence to suggest that regular exercise during pregnancy may reduce the length of labor and decrease complications during delivery (Bungum et al., 2000, Sternfeld, 1997). Regular exercise may also help prevent some of the negative health outcomes that often occur from living a sedentary lifestyle during pregnancy, such as decreased cardiovascular fitness, excessive weight gain, increased risk of gestational diabetes mellitus (Bung, Artal, Khodiguian, & Kjos, 1991), pre-eclampsia (Sorensen et al., 2003), and difficulty psychologically coping with the concomitant physical changes during pregnancy (Wolfe & Mottola, 2000). Beyond this, physical activity during pregnancy may result in physical and psychological benefits in the post-partum period (Sampselle, Seng, Yeo, Killion, & Oakley, 1999). Lastly, given that women who engage in exercise during pregnancy tend to continue their exercise regimens postpartum, the beneficial effects of exercise are likely to continue long past pregnancy (Clapp, 1990). Consequently, it is advisable that pregnant women, assuming an uncomplicated pregnancy, engage in 30 min or more of moderate-intensity exercise a day on most, if not all, days of the week (ACOG, 2002).

Pregnant women encounter many discomforts during pregnancy (Davis, 1996), including restless sleep, shorter sleep duration, and difficulty falling asleep (Mindell & Jacobson, 2000). Inadequate or disturbed sleep is associated with numerous negative biopsychosocial and biophysical health outcomes among adults, including clinical depression, cardiovascular disease, type-2 diabetes, obesity, and all-cause mortality (Sigurdson & Ayas, 2007). Impaired sleep during pregnancy can also affect maternal well-being (Lee & Kimble, 2009). Additionally, maternal work schedules during pregnancy may also influence sleep, with work shift-induced sleep deprivation possibly leading to fetal growth impairment or other pregnancy-related complications (Bonzini, Palmer, Coggon, Cromi, & Ferrario, 2011). Clearly, there are numerous benefits associated with physical activity participation during pregnancy, with empirical evidence further indicating that it may help improve some of the discomforts associated with pregnancy (Horns et al., 1996, Smith and Michel, 2006); however, we currently have a limited understanding of the influence of physical activity on sleep during pregnancy.

To provide insight into the potential sleep-enhancing benefit of physical activity among pregnant women and to therefore see if physical activity may serve as a non-pharmacological treatment for sleep disorders during pregnancy, we reviewed the extant literature. In a large, population-based epidemiological study in the general population, Loprinzi and Cardinal (2011) reported that, after controlling for important confounding variables, participants meeting physical activity guidelines, compared to those not meeting guidelines, were less likely to feel overly sleepy during the day, have leg cramps while sleeping and have difficulty concentrating when tired. Although few studies have examined whether gender differences occur, a meta-analysis of acute and chronic exercise demonstrated a larger influence on sleep in women, compared to men (Kubitz, Landers, Petruzello, & Han, 1996). With respect to the link between physical activity and sleep among pregnant women, we found only one empirical study examining this association. Borodulin et al. (2010) examined the cross-sectional association of self-reported physical activity and self-reported sleep quality and duration among 1259 pregnant women 24–29 weeks’ gestation. Overall, they found that self-reported physical activity was not strongly associated with sleep quality or duration. Importantly, though, their study employed a subjective measure of physical activity that may have attenuated the relationship between physical activity and sleep through its widely established potential measurement error, including recall, misclassification bias, and social desirability effects.

To overcome this limitation and to expand upon our knowledge base regarding the association between physical activity and sleep among pregnant women, the present study sought to examine this relationship using an objective measure of physical activity (i.e., accelerometry). Accelerometry provides important objectively-measured information on the frequency, intensity, and duration of physical activity. Also, to increase the generalizability of our findings to more diverse samples of pregnant women, we conducted this study using a nationally representative sample of pregnant women. Therefore, the purpose of the present study was to examine the association between objectively-measured physical activity and sleep in a nationally representative sample of U.S. pregnant women. We hypothesized that objectively-measured physical activity would be positively associated with a variety of self-reported sleeping-related parameters among pregnant women.