LETTER TO THE EDITOR

Quality of Sleep, Sleep Duration and Depressive State

To the Editor:Bansi et al.1 mentioned that combinations of sleep

disorders, short sleep duration and quality of sleepwere associated with increased risk in the prevalenceof hypertension. Cappuccio et al.2 conducted a system-atic review and meta-analysis for the effect of sleepduration on cardiovascular diseases. They could notevaluate sleep disorders and quality of sleep simulta-neously because of the lack of information. Appropri-ate sleep duration differs from person to person, and Isuppose that there is no standard or reference valuefor sleep duration to predict human health. Further-more, obstructive sleep apnea syndrome (OSAS) is arisk factor of hypertension,3 and OSAS and hyperten-sion interact on arterial stiffness.4 Taking together,selection of parameters is important for risk assess-ment of hypertension. On this point, Bansi et al.1 con-ducted appropriate research using several sleepparameters simultanelously.

By the way, Fernandez-Mendoza et al.5 reportedthat anxiety and lack of stress coping accelerated theunderestimation of objective sleep duration by sleeppolygraphy among insomniacs. This means that sleepdisorders, sleep duration and quality of sleep shouldbe evaluated in combination with mental status. Theauthor presents here the association between sleepduration and depressive state by considering perceivedsleep quality (refreshment by sleep).

The target subjects were employees of a company inJapan. Age of the subjects ranged from 20 to 60 andthe number of subjects was 117 (113 males and fourfemales). Simple summation of each item score (0–3)for Patient Health Questionnaire nine-item version(PHQ-9)6 was adopted in this study. Sleep durationwas categorized as follows: (I) under 5 h, (II) 5–6 h,(III) 6–7 h, and (IV) 7 h or more. Refreshment bysleep was declared binary as ‘‘Yes’’ or ‘‘No.’’

Percent of refreshment by sleep stratified by four cat-egories of sleep duration (I to IV) were 0%, 22.2%,76.2% and 100%. In 62 subjects who replied ‘‘refresh-ment by sleep’’ as ‘‘No,’’ the age-adjusted means andstandard errors of PHQ-9 stratified by categories ofsleep duration (I to III) were 10.2�1.37, 5.3�0.78, and6.8�1.66, respectively. There was a significant differ-ence in the mean value of PHQ-9 between group I andgroup II by multiple comparison (P<0.05).

In contrast, there was no significant difference in themean value of PHQ-9 among three groups whodeclared positive answer on ‘‘refreshment by sleep’’(n=55). The means and standard errors of PHQ-9 withadjusted age stratified by three categories of sleepduration (II to IV) were 5.4�1.19, 2.7�0.74, and4.7�1.19, respectively (Figure 1).

Although this is a cross-sectional study, there wasan effect of perceived sleep quality on the associationbetween sleep duration and depressive state. Namely,subjective sleep duration was negatively related todepressive state evaluated by PHQ-9 in subjects whofailed refreshment by sleep. In subjects with refresh-ment by sleep, there was no change in score of PHQ-9stratified by sleep duration.

Disclosures: None.

Tomoyuki Kawada, MDFrom the Department of Hygiene and Public Health,

Nippon Medical School, Sendagi, Bunkyo-Ku, Tokyo,Japan

References1. Bansil P, Kuklina EV, Merritt RK, et al. Associations between sleep

disorders, sleep duration, quality of sleep, and hypertension: resultsfrom the National Health and Nutrition Examination Survey, 2005to 2008. J Clin Hypertens (Greenwich). 2011;13:739–743.

2. Cappuccio FP, Cooper D, D’Elia L, et al. Sleep duration predictscardiovascular outcomes: a systematic review and meta-analysis ofprospective studies. Eur Heart J. 2011;32:1484–1492.

3. Baguet JP, Barone-Rochette G, Pepin JL. Hypertension and obstruc-tive sleep apnoea syndrome: current perspectives. J Hum Hypertens.2009;23:431–443.

4. Drager LF, Bortolotto LA, Figueiredo AC, et al. Obstructive sleepapnea, hypertension, and their interaction on arterial stiffness andheart remodeling. Chest. 2007;131:1379–1386.

5. Fernandez-Mendoza J, Calhoun SL, Bixler EO, et al. Sleep mispercep-tion and chronic insomnia in the general population: role of objectivesleep duration and psychological profiles. Psychosom Med.2011;73:88–97.

6. Kroenke K, Spitzer RL, Williams JB. The PHQ-9: validity of a briefdepression severity measure. J Gen Intern Med 2001;16:606–613.

FIGURE 1. Mean values of PHQ-9 score stratified by four groups ofsleep duration in subjects who received or failed to receive refresh-ment by sleep.

doi: 10.1111/j.1751-7176.2012.00610.x

Official Journal of the American Society of Hypertension, Inc. The Journal of Clinical Hypertension 1