Dietary phytochemical index and sleep quality: a cross-sectional study from Turkey

Poor sleep quality is an increasing public health concern. Phytochemicals are suggested to have beneficial effects on sleep due to their antioxidant and anti-inflammatory properties. The aim of this study was to investigate the relationship between the Dietary Phytochemical Index (DPI), an alternative method for estimating dietary phytochemical intake, and sleep quality.

The sample of this cross-sectional study consisted of university students between the ages of 19-29 studying at Ankara University. The study data were obtained by face-to-face interview using a questionnaire form. The questionnaire form included general information, anthropometric measurements, Pittsburgh Sleep Quality Index (PSQI), International Physical Activity Questionnaire (short form) and a 24-hour dietary recall. DPI was calculated as the percentage of daily energy intake from phytochemical-rich foods: DPI = (kcal from phytochemical-rich foods / total kcal) × 100.

This study included 472 university students. The participants were classified according to their DPI scores as < 10.00 first tertile (T1), 10.00-27.14 s tertile (T2), > 27.14 third tertile (T3). The mean DPI score of the participants was 20.45. The frequency of individuals aged ≥ 22 years, overweight, non-smokers, and those with moderate physical activity was significantly higher in the lowest DPI tertile (p < 0.05). Total PSQI, sleep quality, habitual sleep efficiency, use of sleeping medication, and daytime dysfunction scores were found to be lower in participants in the highest DPI tertile. (p < 0.05). Participants in the highest tertile of the DPI had a 14% lower odds of poor sleep quality than those in the lowest tertile (OR = 0.861, 95% CI, 0.757-0.980).

As a result, this study found that sleep quality was better in those in the highest DPI tertile. Longitudinal studies with large samples are needed to confirm the relationship between DPI and sleep quality.