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Long Sleep Duration is Associated With Serum Cholesterol in the Elderly: The Rotterdam Study

From the Department of Epidemiology and Biostatistics (J.F.B., A.H., J.C.M.W., H.T.), Erasmus Medical Center, Rotterdam, The Netherlands; Department of Public Health and Primary Care (J.F.B., A.K.N.), Leiden University Medical Center, Leiden, The Netherlands; TNO Built Environment and Geosciences (H.M.E.M.), Netherlands Organisation for Applied Research TNO, Delft, The Netherlands; Department of Psychiatry (J.H.M.T.), Erasmus Medical Center, Rotterdam, The Netherlands; and Department of Child and Adolescent Psychiatry (H.T.), Erasmus Medical Center, Rotterdam, The Netherlands.

Address correspondence and reprint requests to Henning Tiemeier, MD, PhD, Department of Epidemiology and Biostatistics, Erasmus Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. E-mail: h.tiemeier{at}erasmusmc.nl

Objective: Epidemiological studies have repeatedly found increased mortality associated with both habitual short and long sleep duration. The mechanisms behind these associations are unclear. We investigated whether objectively measured sleep duration, time in bed, and sleep fragmentation were associated with total cholesterol and high density lipoprotein (HDL) cholesterol in community-dwelling elderly.

Methods: This cross-sectional study was conducted among 768 participants of the Rotterdam Study, aged 57 to 97 years. Sleep parameters were assessed with actigraphy, a validated method that infers wakefulness and sleep from arm movement. Cholesterol levels in serum were determined in fasting blood samples. All regression analyses were adjusted for age, gender, body mass index, smoking, depressive symptoms, and heart failure.

Results: Sleep duration was positively associated with total cholesterol level: β = 0.11 (95% confidence interval = 0.03–0.18) mmol/l per hour of sleep. Persons who slept longer, and spent more time in bed, also had a higher total/HDL cholesterol ratio. A less fragmented sleep was also associated with higher total cholesterol. Some of these associations showed significant interactions with age. The association between time in bed and total/HDL ratio was mainly driven by persons aged <65, whereas the relationship between sleep fragmentation and total cholesterol level was most prominent in persons aged 70.

Conclusions: A longer sleep duration was related to higher total cholesterol level and a higher total/HDL cholesterol ratio. Two separate mechanisms, a longer time in bed and sleep fragmentation, seem to explain these associations in different age categories.

Key Words: sleep duration • sleep fragmentation • actigraphy • cholesterol • elderly • epidemiology

Abbreviations: CI = confidence interval; BMI = body mass index; HDL = high density lipoprotein; LDL = low density lipoprotein; TIB = time in bed; TST = total sleep time; CES-D = Center for Epidemiologic Studies Depression Scale; PSQI = Pittsburgh Sleep Quality Index.