Why CVD risk is linked to poor sleep quality

Women who have poor sleep quality are also eating more food and have lower-quality diets – all of which are factors that increase cardiovascular disease (CVD) risk. Sleep quality includes several factors related to the ability to fall asleep and stay asleep.

The cross-sectional study appeared in the Journal of the American Heart Association. The authors aimed to examine the associations of both subclinical and clinical measures of sleep quality (including overall sleep quality, sleep-onset latency, and insomnia) with energy and macronutrient intakes as well as with intake of specific food associated with CVD risk. 

Methods
Data for the study were obtained from women who were enrolled in a 1-year prospective cohort study of sleep and CVD risk as part of the American Heart Association Go Red for Women Strategically Focused Research Network. Eligible participants were nonpregnant women between ages 20 and 79 who were recruited from New York-Presbyterian Hospital/Columbia University Irving Medical Center. 

The authors measured habitual sleep quality at baseline through two validated, self-report tools: the Pittsburgh Sleep Quality Index (PSQI) and the

(ISI). The PQSI assesses sleep patterns over the past month, while the ISI is composed of seven items measuring five different components of insomnia (severity of insomnia symptoms, satisfaction with current sleep, extent to which current sleep interferes with daily function, perception of sleep problems, and the extent to which sleep problems are worrisome). Diet was assessed using the Block Brief Food Frequency Questionnaire (FFQ), which includes a list of approximately 70 food items that are consumed by multiple racial and ethnic groups and measures how frequently each item was consumed over the past year and the amount eaten. The authors used linear regression models adjusted for confounding variables to test relationships between sleep and diet variables. 

Findings
The study included subject characteristics and sleep metrics for 495 women in analysis. The mean age of participants was 37 ± 16 years and 61% of the sample was a racial or ethnic minority. Mean body mass index (BMI) was 25.9 ± 5.7 kg/m²with a balanced proportion of women with overweight/obesity compared with normal weight (51% vs 49%, P= 0.93). Average sleep time was 6.76 ± 1.24 hours. Thirty-eight percent of the cohort had poor sleep quality or some insomnia. In regard to sleep duration, 27.5% of the sample had short sleep duration (< 7 h/night) with poor sleep quality, and 24.6% had short sleep duration with insomnia. Participants reported consuming 1433 ± 862 kcal/d, and on average, exceeded recommendations for total and saturated fat intakes along with added sugars. However, they failed to meet most recommendations for whole grains, fiber, and dairy intakes.  

The authors found that higher PSQI scores were indicative of poorer sleep quality, were associated with a greater total weight of food consumed (ß = 14.9 ± 6.6 g, P = 0.02) as well as higher intakes of added sugars (ß = 0.44  ± 0.21 g/1000 kcal, P = 0.04) and caffeine (ß = 0.84 ± 0.27 mg, P < 0.01). However, PQSI scores were inversely related to dairy intake (ß = -0.01 ± 0.01 servings/1000 kcal, P = 0.03). This relationship indicates that poorer sleep quality was associated with lower dairy intake. The authors also found a significant interaction between PSQI scores and age on whole grain intake (P= 0.04). Higher PSQI scores were associated with lower grain intake in younger women (ß = -0.04 ± 0.02 servings/1000 kcal, P = 0.02), but this relationship was not significant in older women. The authors noted that poor sleep quality was related to a greater consumption of added sugars (ß = 3.41 ± 1.57 g/1000 kcal, P = 0.03) and caffeine (ß = 4.57 ± 2.04 mg, P = 0.03) when compared with good sleep quality.

Women with sleep-onset latency > 60 minutes had higher intakes of food by weight (ß = 235.2, P < 0.01) and energy (ß = 426, P < 0.01). They also had lower intakes of grains (ß = -0.37, P = 0.01) than women with sleep-onset latency ≤ 15 minutes. Greater insomnia severity was associated with higher intakes of food by weight (ß = 9.4, P = 0.02) and energy (ß = 17, P = 0.01) consumed and lower total (ß = 17, P  =0.01).The relationship was inversely related to total fat  consumed (ß = -0.15, P = 0.01) and unsaturated fat intakes (ß = -0.11, P  < 0.01).

Conclusions
Based on these findings, the authors believe that diet plays an important role in a woman’s sleep quality. Poor sleep quality was associated with greater food intake and lower-quality diet. The authors note that one interpretation of their findings could be that diet quality affects the time it takes to fall asleep, which could in turn influence CVD risk via poor sleep quality. They suggest that future studies should explore whether promoting sleep quality could enhance efforts to improve cardiometabolic health in women.