Gender-Specific Associations of Short Sleep Duration With Prevalent Hypertension
To the Editor:
We read the interesting recent article by Cappuccio et al,1 who found that sleep deprivation was positively associated with hypertension among women. We examined this hypothesis in our ongoing Heinz Nixdorf Recall Study, a prospective population-based cohort study.2,3 Interestingly, we were able to corroborate the gender specificity of the association between short duration of sleep (≤5 hours per night) and prevalence of hypertension, although we observed a weaker association.
The age-adjusted prevalence ratio in our study was 1.05 (95% CI: 0.89 to 1.23) among men and 1.24 (95% CI: 1.04 to 1.46) among women. Furthermore, we observed that daily long siesta (midday naps) is associated with excessively short and long sleep durations at night. However, adjustment for regular siesta did not change the estimates (Table).
Some points deserve critical appraisal. First, the authors state, “among women, in fully adjusted analyses, short duration of sleep (≤5 hours per night) was associated with higher risk of hypertension compared with the group sleeping 7 hours (OR [odds ratio]: 2.01; 95% CI: 1.13 to 3.58).” This result does not correspond with any result in their tables.
Second, in their cross-sectional analysis, the authors calculated prevalence odds ratios and interpreted them as relative risks. However, the odds ratio does not appropriately depict the clinical and public health relevance in light of the high prevalence of hypertension: in their data, the prevalence of hypertension among women who sleep ≤5 hours is 36.9% and among women who sleep 7 hours per night is 25.5%. The unadjusted relative risk (ratio of prevalences) of Cappuccio et al1 of 1.45 is considerably closer to the null value than the reported unadjusted odds ratio of 1.72.
S.M. has received research support from and has participated in speaking engagements for Sanofi-Aventis Deutschland GmbH. K.H.J. has received research support from 3M Medica Deutschland GmbH, Apogepha Arzneimittel GmbH, Astra-Zenica GmbH, Boeringer Ingelheim Pharma GmbH, Dr Regenold GmbH, Ferring Arzneimittel GmbH, Fujifilm Europe GmbH, IFAG Basel AG, LIPHA Arzneimittel GmbH, MEDICE Arzneimittel Putter GmbH, Merck KGaA, Neuro-Consil GmbH, Sanofi-Aventis Deutschland GmbH, Takeda Pharma GmbH, and UCB GmbH and is a consultant to the Weinberg Group. A.S., S.M., and R.E. report no conflicts.
Cappuccio FP, Stranges S, Kandala NB, Miller MA, Taggart FM, Kumari M, Ferrie JE, Shipley MJ, Brunner EJ, Marmot MG. Gender-specific associations of short sleep duration with prevalent and incident hypertension: the Whitehall II Study. Hypertension. 2007; 50: 693–700.
Schmermund A, Möhlenkamp S, Stang A, Grönemeyer D, Seibel R, Hirche H, Mann K, Siffert W, Lauterbach K, Siegrist J, Jöckel KH, Erbel R. Assessment of clinically silent atherosclerotic disease and established and novel risk factors for predicting myocardial infarction and cardiac death in healthy middle-aged subjects: rationale and design of the Heinz Nixdorf RECALL Study. Risk Factors, Evaluation of Coronary Calcium and Lifestyle. Am Heart J. 2002; 144: 212–218.