The authors have declared that no competing interests exist.
Conceived and designed the experiments: DL FB JBR. Analyzed the data: DL FB JBR FS BF. Contributed to the writing of the manuscript: DL FB JBR FS BF.
A significant U-shaped association between sleep duration and several morbidity (obesity, diabetes or cardiovascular disease) and mortality risks has been regularly reported. However, although the physiological pathways and risks associated with “too short sleep” (<5 hours/day) have been well demonstrated, little is known about “too much sleeping”.
To explore socio-demographic characteristics and comorbidities of “long sleepers” (over 10 hours/day) from a nationally representative sample of adults.
A cross-sectional nationally representative sample of 24,671 subjects from 15 to 85-year-old. An estimated total sleep time (TST) on non-leisure days was calculated based on a specifically designed sleep log which allows to distinguish “long sleepers” from “short sleepers” (<5 hours/day). Insomnia was assessed according to the International classification of sleep disorders (ICSD-2).
The average TST was 7 hours and 13 minutes (+/− 17 minutes). Six hundred and twelve subjects were “long sleepers” (2.7%) and 1969 “short sleepers” (7.5%). Compared to the whole group, “long sleepers” were more often female, younger (15–25 year-old) or older (above 65 year-old), with no academic degree, mostly clerks and blue collar workers. “Long sleepers” were significantly more likely to have psychiatric diseases and a greater body mass index (BMI). However, long sleep was not significantly associated with the presence of any other chronic medical disease assessed. Conversely, short sleep duration was significantly associated with almost all the other chronic diseases assessed.
In the general population, sleeping too much was associated with psychiatric diseases and higher BMI, but not with other chronic medical diseases.
It is generally recommended as one of the major rules for good health in children, but also in adults, to have a sufficient amount of sleep everyday
Most experts agree that sleep has now to compete more and more with multiple tasks in our today's 24-hour society. It results in a severe sleep duration reduction around the planet, especially for adolescents and young adults
Although scientists are still studying the concepts of basal sleep need, increasing evidence tends to show that sleeping too little or too much impacts severely on health with a U-shaped association between short and long sleep duration and morbidity
The metabolic, behavioral and epidemiological rationale explaining the impact of short sleep duration on health is, however, stronger than that the one of long sleep duration.
Sleep research has certainly shown that sleeping too little can affect memory, immunity, and jeopardize safety
The evidence that long sleep is associated with obesity, diabetes, hypertension or other cardiovascular diseases
The aim of this study was, therefore, to more precisely study “long sleepers”, using a clear cut-off for sleep duration, in a nationally representative sample of subjects and by so trying to better understand the association between long sleep duration and health.
Analyses were based on a nationally representative, cross-sectional sample of French adults, collected every 5 years since 1990, the “Baromètre Santé” (BS) (Health Barometer) and conducted by INPES (Institut National de Prévention et d'Education pour la Santé). A common INPES BS study protocol standardizes instrumentation, sampling methods, and data collection procedures at each step, with data cleaning and data set construction performed centrally
The methodology is a cross-sectional study based on telephone surveys with a randomized selection of households and subjects interviewed, using a computerized system (CATI) to select mobile phone and all home phone numbers with no restriction. If the phone is not answered or busy, the interviewers phone repeatedly for up to 40 times at different times of the week and of the day. These different samples were aggregated and weighted to be representative of the general French population (2008 census
To be eligible, each household had to include at least one French speaking individual between 15 and 85 year-old (yo). The subject was randomly selected from among the household residents; if he/she declined to participate, the household was not selected.
Participation was anonymous and voluntary; the study protocol was approved by the French Commission on Information Technologies and Liberties (Commission Nationale Informatique et Libertés) based on the anonymous nature of the study and the guarantee that the phone numbers selected would be erased from the database after the study.
Sections investigating sleep assessments were introduced for the first time in the BS-2010. These sleep-specific measurements were based on validated sleep-logs recommended for the assessment of sleep in adults
1) ‘When you have to work (to be active) the next day, at what time do you usually switched off the light to go to sleep?
2) ‘When you have to work (to be active) the next day, at what time do you usually waked up?’
3) ‘How long does it usually take for you to fall asleep?’
4) ‘If you have awakenings during the night, how long do they usually last (minutes)?
TST was defined as the difference between the time at which the participant switches off the light and the time at which they wake up, discounting the time needed to fall asleep + the time awaken.
- Alcohol use was assessed on AUDIT Score
- To assess chronic diseases, “the interview included 8 questions on chronic diseases which were carefully designed. The first one was “Do you suffer from any chronic disease, i.e., a disease you had from a long time (at least 6 months) and which may benefit of regular treatment (i.e: diabetis, astma…): Yes, No, Don't know.” Question 2: which one and the interviewer has the possibility of checking the exact (s) chronic disease(s) from an open list of 232 chronic diseases”. Based on these list there are 6 questions on visiting doctors, nurses or other medical staff, hospitalisations in the last 12 months, blood samples or dietetary recommendations, which allow the interviewer to come back to the subject to get more details on the chronic disease. Therefore subjects did not self-report their illnesses but follow specific guidelines which allow us to clearly identify which chronic diseases were diagnosed including psychiatric diseases.
- To complete the psychiatric medical history on the present time, psychological distress was assessed by the SF-36 mental health sub score
- Feelings of precariousness (“i.e. the feeling of having not enough ressources or social support to avoid powerty, professional failure, poor health or life accidents), reports of a serious and traumatic event before 18 yo and verbal, physical or sexual violence during the 12 months prior to the survey were assessed using specific questionnaires on personal background
Bi-variate and multivariable logistic regression models were applied to investigate whether risk factors were independently associated with short TST and long TST. Analyses were performed using the R 2.12.1 software. The statistics presented (percentages, odds ratios) correspond to weighted and adjusted results. We used Pearson's chi-square tests in the bi-variate analysis; odds ratio (OR) are presented with their 95% confidence interval.
A total of 24,671 individuals (10,962 males and 13,709 females) participated in the study; those households who refused to participate were replaced by a same profile subject selected in the basis (equally for mobile phones and for home phones). Therefore, the final sample was representative of the French national population (based on the last census)
The average TST was 7 hours and 13 minutes (+/− 17 minutes) and was significantly longer in females than in males (7 hours 18 minutes (+/− 21 minutes) vs. 7 hours 07 minutes (+/− 22 minutes); p<0,001). TST duration curves with age were similar in males and females (see
Total sleep time was defined as the difference between the time at which the participant switched off the light and the time of day they woke up, discounting the time needed to fall asleep.
TST (Total Sleep Time) | <4 hours | [4–5 hours[ | [5–6 hours[ | [6–7 hours[ | [7–8 hours[ | [8–9 hours[ | [9–10 hours[ | > = 10 hours | |
males (reference) | 10962 | 3.5 | 5.0 | 12.2 | 25.7 | 31.1 | 15.5 | 4.9 | 2.0 |
females | 13709 | 3.3 | 3.7 | 8.8 | 20.4 | 32.4 | 21.9 | 7.1 | 2.5 |
15–19 years old (reference) | 738 | 3.3 | 4.8 | 9.8 | 22.0 | 28.6 | 16.6 | 8.3 | 6.6 |
20–25 years old | 2233 | 2.8 | 4.3 | 8.6 | 20.1 | 27.6 | 21.4 | 9.1 | 6.0 |
26–34 years old | 3796 | 2.7 | 4.1 | 9.8 | 23.0 | 32.5 | 19.9 | 5.7 | 2.3 |
35–44 years old | 5251 | 3.6 | 4.8 | 11.0 | 24.6 | 33.9 | 16.5 | 4.4 | 1.2 |
45–54 years old | 4504 | 3.4 | 5.0 | 11.7 | 25.9 | 33.9 | 14.7 | 4.3 | 1.1 |
55–64 years old | 4972 | 4.1 | 3.7 | 10.6 | 23.1 | 30.8 | 19.5 | 6.4 | 1.7 |
65–74 years old | 2923 | 3.3 | 3.8 | 10.3 | 18.5 | 29.8 | 24.1 | 7.8 | 2.3 |
75–85 years old | 254 | 4.6 | 4.9 | 9.8 | 15.7 | 29.4 | 25.1 | 8.8 | 1.7 |
<Baccalaureate (Reference) | 11926 | 4.6 | 5.4 | 10.9 | 21.7 | 28.5 | 18.7 | 7.3 | 2.9 |
Baccalaureate | 4626 | 2.0 | 3.5 | 10.1 | 23.6 | 33.3 | 20.1 | 5.4 | 2.0 |
> Baccalaureate | 8119 | 1.6 | 2.5 | 9.7 | 25.5 | 38.5 | 17.9 | 3.5 | 1.0 |
Farmers (Reference) | 489 | 3.9 | 3.6 | 9.9 | 19.3 | 30.8 | 23.8 | 7.3 | 1.3 |
Artisans | 1369 | 3.4 | 5.3 | 13.0 | 23.4 | 29.8 | 18.4 | 5.4 | 1.3 |
Upper level executive | 4660 | 1.9 | 2.6 | 10.6 | 27.2 | 36.9 | 16.5 | 3.5 | 0.8 |
Middle-level | 6800 | 2.1 | 3.4 | 9.9 | 24.4 | 35.0 | 19.4 | 4.5 | 1.2 |
White collars | 6589 | 4.1 | 4.6 | 9.6 | 20.3 | 31.0 | 20.2 | 7.2 | 3.0 |
Blue collars | 4627 | 4.7 | 6.2 | 11.4 | 22.0 | 26.6 | 17.7 | 7.6 | 3.7 |
Other | 137 | 4.7 | 3.2 | 7.6 | 21.9 | 23.9 | 11.2 | 19.5 | 8.0 |
No (Reference) | 18181 | 3.2 | 4.0 | 10.2 | 22.9 | 32.3 | 19.2 | 5.9 | 2.3 |
Yes | 6490 | 4.3 | 6.0 | 11.9 | 23.0 | 29.2 | 16.7 | 6.6 | 2.3 |
Weighted percentages, Pearson's chi square test for bi-variate analysis: ***p<0.001, **p<0.01, *p<0.05.
TST (Total Sleep Time) | <4 hours | [4–5 hours[ | [5–6 hours[ | [6–7 hours[ | [7–8 hours[ | [8–9 hours[ | [9–10 hours[ | > = 10 hours | |
No overweight, no obesity (Reference) | 14894 | 3.1 | 4.1 | 9.6 | 23.0 | 32.9 | 19.1 | 5.9 | 2.4 |
Overweight | 7029 | 3.1 | 4.6 | 11.7 | 23.2 | 31.2 | 18.6 | 5.8 | 1.7 |
Obesity | 2748 | 5.6 | 5.0 | 11.8 | 21.7 | 27.6 | 17.5 | 7.6 | 3.2 |
No (Reference) | 20241 | 3.0 | 4.0 | 10.6 | 23.7 | 33.4 | 18.6 | 5.0 | 1.7 |
Yes | 4430 | 4.8 | 5.7 | 10.1 | 20.1 | 25.9 | 19.3 | 9.7 | 4.5 |
No perceived precariousness (Reference) | 14591 | 2.4 | 3.4 | 9.8 | 23.1 | 34.1 | 19.5 | 5.6 | 2.1 |
At the edge | 6619 | 3.7 | 4.8 | 11.2 | 22.7 | 30.9 | 18.7 | 5.8 | 2.3 |
Yes | 3461 | 6.6 | 7.4 | 11.7 | 22.7 | 24.7 | 16.1 | 8.1 | 2.9 |
No (Reference) | 19961 | 3.0 | 3.7 | 9.9 | 22.8 | 32.6 | 19.4 | 6.1 | 2.3 |
Yes | 4710 | 5.1 | 7.1 | 12.7 | 23.6 | 27.9 | 15.8 | 5.7 | 2.2 |
No (Reference) | 13156 | 2.7 | 3.6 | 9.8 | 23.1 | 33.7 | 19.5 | 5.6 | 2.0 |
Yes | 11515 | 4.2 | 5.3 | 11.1 | 22.7 | 29.6 | 18.0 | 6.5 | 2.6 |
No (Reference) | 21648 | 2.8 | 3.9 | 10.1 | 23.1 | 32.8 | 19.2 | 5.9 | 2.2 |
Yes | 3023 | 8.0 | 7.4 | 12.9 | 21.7 | 24.4 | 15.9 | 6.9 | 2.9 |
No (Reference) | 18785 | 3.0 | 4.1 | 10.3 | 23.1 | 32.4 | 18.8 | 5.9 | 2.3 |
Yes | 5886 | 4.6 | 5.2 | 11.0 | 22.2 | 29.5 | 18.8 | 6.4 | 2.2 |
For each health variable the absence of risk factor was considered as the reference and compared to the other groups within the eight total sleep time groups retained (from <4 hours to > = 10 hours). Weighted percentages expressed the percentages of subject with each risk factors who reported sleeping between x and y hours.
Pearson's chi square test for bi-variate analysis: ***p<0.001, **p<0.01, *p<0.05.
Short TST<5 hours | Long TST> = 10 hours | ||||||
Variables | N | % |
Adjusted OR |
CI 95% | % |
Adjusted OR |
CI 95% |
Males (reference) | 10899 | 8.5 | - 1 - | 2.0 | - 1 - | ||
Females | 13523 | 7,0 | 0.8*** | [0.7–0.8] | 2.5 | 1.1 | [0.9–1.3] |
15–19 years old (reference) | 724 | 8.2 | - 1 - | 6.6 | - 1 - | ||
20–25 years old | 2203 | 7.1 | 1.0 | [0.7–1.5] | 5.8 | 0.9 | [0.6-1.3] |
26–34 years old | 3756 | 6.6 | 0.9 | [0.7–1.3] | 2.3 | 0.4*** | [0.3–0.6] |
35–44 years old | 5213 | 8.3 | 1.2 | [0.9–1.6] | 1.2 | 0.2*** | [0.1–0.3] |
45–54 years old | 4460 | 8.4 | 1.2 | [0.9–1.6] | 1.1 | 0.2*** | [0.1–0.3] |
55–64 years old | 4932 | 7.8 | 1.2 | [0.9–1.7] | 1.7 | 0.3*** | [0.2–0.4] |
65–74 years old | 2885 | 7.1 | 1.0 | [0.7–1.4] | 2.3 | 0.4*** | [0.2–0.6] |
75–85 years old | 249 | 9.1 | 1.4 | [0.8–2.3] | 1.7 | 0.3* | [0.1–0.8] |
<Baccalaureate (Reference) | 11776 | 10.0 | - 1 - | 2.9 | - 1 - | ||
Baccalaureate | 4582 | 5.5 | 0.7*** | [0.6–0.8] | 2.0 | 0.7** | [0.5–0.9] |
> Baccalaureate | 8064 | 4,0 | 0.5*** | [0.4–0.6] | 1.0 | 0.6*** | [0.4–0.8] |
Normal (Reference) | 14846 | 7.2 | - 1 - | 2.4 | - 1 - | ||
Overweight | 7029 | 7.8 | 1.0 | [0.9–1.1] | 1.7 | 1.0 | [0.8–1.2] |
Obesity | 2547 | 10.5 | 1.2** | [1.1–1.4] | 3.2 | 1.3 | [1.0–1.7] |
Farmers (Reference) | 481 | 7.6 | - 1 - | 1.3 | - 1 - | ||
Craftsmen | 1363 | 8.8 | 1.3 | [0.8–1.9] | 1.2 | 1.5 | [0.6–3.7] |
Upper level executive | 4636 | 4.4 | 0.9 | [0.6–1.3] | 0.8 | 1.1 | [0.4–2.6] |
Middle-level | 6750 | 5.5 | 1.0 | [0.7–1.4] | 1.2 | 1.3 | [0.6–3.1] |
White collar | 6482 | 8.7 | 1.1 | [0.8–1.6] | 3.0 | 2.3* | [1.0–5.3] |
Blue collar | 4578 | 10.9 | 1.4 | [0.9–2.0] | 3.7 | 2.5* | [1.1–5.7] |
Other | 132 | 8.2 | 1.2 | [0.6–2.4] | 8.3 | 3.4* | [1.1–10.3] |
No (Reference) | 18012 | 7.2 | - 1 - | 2.3 | - 1 - | ||
Yes | 6410 | 10.4 | 1.4*** | [1.2–1.5] | 2.3 | 1.0 | [0.8–1.3] |
No (Reference) | 20077 | 7.0 | - 1 - | 1.7 | - 1 - | ||
Yes | 4345 | 10.4 | 0.9 | [0.8–1.0] | 4.5 | 1.7*** | [1.4–2.1] |
No (Reference) | 14475 | 5.7 | - 1 - | 2.1 | - 1 - | ||
At the edge | 6542 | 8.3 | 1.2** | [1.1–1.3] | 2.3 | 0.9 | [0.8–1.2] |
Yes | 3405 | 14.0 | 1.7*** | [1.5–2.0] | 2.9 | 0.9 | [0.7–1.2] |
No (Reference) | 19759 | 6.7 | - 1 - | 2.3 | - 1 - | ||
Yes | 4663 | 12.2 | 1.6*** | [1.4–1.8] | 2.2 | 0.9 | [0.7–1.2] |
No (Reference) | 13033 | 6.2 | - 1 - | 2.0 | - 1 - | ||
Yes | 11389 | 9.4 | 1.2*** | [1.1–1.3] | 2.6 | 1.1 | [0.9–1.3] |
No (Reference) | 21430 | 6.7 | - 1 - | 2.2 | - 1 - | ||
Yes | 2992 | 15.3 | 2.0*** | [1.7–2.2] | 2.9 | 1.2 | [0.9–1.6] |
No (Reference) | 18586 | 7.1 | - 1 - | 2.3 | - 1 - | ||
Yes | 5836 | 9.9 | 1.2* | [1.0–1.3] | 2.2 | 1.3 | [1.0–1.6] |
: Weighted percentages. Pearson's chi square test for bivariate analysis: ***p<0.001; **p<0.01; *p<0.05.
: Adjusted on all shown measures. Wald test: ***p<0.001; **p<0.01; *p<0.05.
- From the all group, 692 (2.7%) individuals reported a TST >10 hours, 143 (0.5%) >11 hours, 43 (0.2%) >12 hours (hypersomnolence).
- Among long sleepers (TST>10 hours), 9.8% (0.26% of the total group) reported an association with being regularly or often sleepy (hypersomnia)
- 0.03% reported severe hypersomnolence (TST>12 hours + non-restorative sleep). Non-restorative sleep was not statistically more reported by “long sleepers” than by the “non long sleepers” group (21.9% vs. 20.8%; NS).
- From the total group, 1,850 individuals reported a TST <5 hours (7.23%) and 814<4 hours (3.3%).
A lower educational level was significantly associated with short or long sleep duration. Long sleep was significantly more frequent in white collar and blue collar workers and short sleep in blue collar workers and craftsmen. Living alone was significantly associated with short sleep.
Subjects with long sleep and short sleep duration were significantly more overweight (BMI>25) and obese (BMI>30) than normal sleepers.
Insomnia was significantly less frequent both in long sleepers and in short sleepers than in the whole group.
Long sleepers did not report more perceived precariousness or violence in the 12 months prior to the survey than did the general population. They, however, did report slightly more psychological distress (SF-36 sub-scale) and violent traumatic events before 18 yo.
Short sleepers reported significantly more psychological distress and more violence in the 12 months prior to the survey, more traumatic events before 18 yo and more perceived precariousness than the whole group.
Long sleepers did not report more or fewer chronic diseases than did the group as a whole including mental or physical diseases. Conversely, short sleepers claimed significantly more associated chronic diseases; these comorbidities are detailed in
Short TST<5 hours | Long TST> = 10 hours | ||||||
Variables | N | % |
Adjusted OR |
CI 95% | % |
Adjusted OR |
CI 95% |
No (Reference) | 22772 | 7,6 | - 1 - | 2,3 | - 1 - | ||
Yes | 1650 | 8,8 | 1,0 | [0,9–1,3] | 1,9 | 1,0 | [0,7–1,5] |
No (Reference) | 24107 | 7,7 | - 1 - | 2,3 | - 1 - | ||
Yes | 315 | 12,8 | 1,5* | [1,0–2,1] | 2,7 | 1,6 | [0,8–3,1] |
No (Reference) | 23438 | 7,6 | - 1 - | 2,3 | - 1 - | ||
Yes | 984 | 11,4 | 1,3* | [1,0–1,6] | 1,9 | 0,9 | [0,6–1,5] |
No (Reference) | 23388 | 7,5 | - 1 - | 2,3 | - 1 - | ||
Yes | 1034 | 13,3 | 1,4** | [1,1–1,7] | 1,5 | 0,8 | [0,5–1,3] |
No (Reference) | 24049 | 7,6 | - 1 - | 2,3 | - 1 - | ||
Yes | 373 | 16,8 | 1,7*** | [1,3–2,3] | 1,5 | 0,7 | [0,3–1,7] |
No (Reference) | 24049 | 7,6 | - 1 - | 2,3 | - 1 - | ||
Yes | 373 | 16,8 | 1,7*** | [1,3–2,3] | 1,5 | 0,7 | [0,3–1,7] |
No (Reference) | 24055 | 7,7 | - 1 - | 2,3 | - 1 - | ||
Yes | 367 | 10,9 | 0,9 | [0,6–1,3] | 2,6 | 1,7 | [0,9–3,1] |
No (Reference) | 24092 | 7,6 | - 1 - | 2,2 | - 1 - | ||
Yes | 330 | 14,6 | 0,9 | [0,7–1,3] | 8,8 | 6,0*** | [3,9–9,3] |
No (Reference) | 24252 | 7,7 | - 1 - | 2,2 | - 1 - | ||
Yes | 170 | 8,1 | 0,6 | [0,3–1,1] | 4,1 | 1,8 | [0,7–4,4] |
No (Reference) | 24222 | 7,7 | - 1 - | 2,3 | - 1 - | ||
Yes | 200 | 9,5 | 1,0 | [0,6–1,8] | 0,5 | 0,3 | [0,0–2,1] |
No (Reference) | 24287 | 7,7 | - 1 - | 2,2 | - 1 - | ||
Yes | 135 | 2,4 | 0,4 | [0,2–1,0] | 7,9 | 3,3** | [1,6–6,9] |
No (Reference) | 7712 | 7,8 | - 1 - | 2,0 | - 1 - | ||
Yes | 353 | 7,9 | 1,0 | [0,7–1,5] | 2,5 | 0,8 | [0,3–1,8] |
: Weighted percentages. Pearson's chi square test for bivariate analysis: ***p<0.001; **p<0.01; *p<0.05.
: Adjusted on all shown measures. Wald test: ***p<0.001; **p<0.01; *p<0.05.
The aim of the study was to better define and characterize individuals with long sleep durations and, as such, we will limit our discussion to these subjects. We believe that the link between short sleep and health has been well documented; findings that are supported by our data.
- A first strength of our study is that we retrieved data on “long sleepers” from an extensive database of 24,671 individuals from a representative group of the general population. To our knowledge, this is the first study that has observed such a large and representative group of long sleepers: 612 individuals had a TST>10 hours, 143>11 hours and 43>12 hours.
We have here to specify that these long sleepers did not have any other sleep disorders according to the ICSD-3rd international classification
Our representative sample shows that long sleep is not limited to the elderly, but also concerns a large proportion of young adults (6.6% of 15–19 yo and 6% of 20–25 yo in our survey). Long sleep was very rare in the 35–54 yo class (1.1%) likely because of occupational- and social-related sleep restrictions. As underlined by Grandner et al.
In addition to the effects of age, short sleep and long sleep were here significantly associated with a lower educational level, which is often found associated with higher co morbidity rates
- In contrast to most of the previous studies observing long sleepers
Obesity has not been consistently found to be associated with long sleep, despite heterogeneous study designs and populations
The association between long sleep and depression is less controversial. In our study, long sleep was associated with a higher rate of depression, but also a higher report of traumatic events in the past, which may partly explain the depressive complaints. In the Whitehall study, long sleepers (>8 hours) also significantly complained of more depressive symptoms than did normal sleepers
Except for obesity and depression, we did not find any significant association between long sleep duration and other comorbidities. This discrepancy between our results and those of previous surveys may be explained by several methodological issues:
The first was the “cut off” we used to define long sleepers. The heterogeneity of possible cut-offs (>8 h, >8.5 h, >9 h, >10 h) has been identified as a major bias in many reviews and meta-analyses
A second possible point of confusion stands on how “long sleep” was assessed. Many studies have hypothesized, using just one simple subjective question: “on the average how many hours do you sleep each night”
A final point that we have already previously discussed is the age. Most studies have focused on the elderly with or without of elderly potentially associated preexisting comorbidities: cancer, cardiovascular diseases
Several important meta-analyses and reviews have reported that long sleep is associated with increased mortality
Our study was not prospective and we cannot comment on differences in mortality. However, we agree with the conclusion of the most recent meta-analysis, that “despite a large body of literature, it is premature to conclude. Careful attention must be paid to measurement, response bias, confounding, and reverse causation in the interpretation of associations between sleep duration and mortality
Our study has several limitations that restrict the conclusions that can be drawn. Due to the cross-sectional design, it did not allow us to establish causality or temporality. Secondly, information about TST was self-reported by the participants. Nevertheless, self-reported TST assessments have been shown to be valid in long sleepers as registered by both actimetry and polysomnography
Except for obesity and depression, we found no risk associated with “sleeping too much” in a nationally representative sample of the general population; not surprisingly, “short sleep” was associated with most of these comorbidities.
We would like to thank Karen Pickett for English-language editing.