Increased Mortality Seen in Those With Changes in Sleep Duration

Both too much sleep and not enough sleep appear to be associated with increased mortality, according to a new longitudinal study.

Sleeping less than 6 hours per night or more than 9 hours per night was associated with almost twice the mortality risk of sleeping 6–8 hours per night, according to an analysis of sleep data from a prospective cohort study of more than 10,000 British civil servants.

The findings were recently presented at a meeting of the British Sleep Society, and the research article has been accepted for publication in the journal Sleep.

The investigators found that a decrease in the amount of time slept was associated with increased mortality from cardiovascular causes. An increase in sleep time was associated with an excess of mortality from all other causes, according to Jane Ferrie, Ph.D., of University College London, and her colleagues.

Previous studies have reported a U-shaped relationship between time spent sleeping and mortality, the investigators said. What has not been looked at by a sleep study before is the effect a change in sleep patterns might have.

The researchers examined sleep data collected from British civil service employees aged 35–55 years who were enrolled beginning in 1985 in a long-term study known as Whitehall II. Baseline sleep duration data were available for 9,781 subjects who were interviewed in 1985–1988, while follow-up data were available for 7,729 who were interviewed again in 1992–1993. Mortality data were available through September 2004.

After adjustment for factors such as age, sex, smoking status, body mass index, cholesterol, and physical activity, those Whitehall II participants who reported sleeping 5 hours or less a night at the first interview had a hazard ratio of death from all causes of 1.24, relative to those who slept 7 hours per night. Those who slept 9 hours or more had a fully adjusted hazard ratio of 1.54.

The fully adjusted hazard ratios of all-cause mortality were slightly higher for those who reported sleep for 5 hours or less and 9 hours or more at the second interview, 1.78 and 1.95, respectively. The risk of death due to cardiovascular causes was relatively greater for those who slept less after the baseline period than for those who slept more.

Participants whose sleep decreased from 6–8 hours a night at the first interview to less than 6 hours at the second interview had a fully adjusted hazard ratio of mortality from cardiovascular cause of 2.04, compared with 1.22 for those who slept more. Those whose sleep increased from 7–8 hours at the first interview to more than 8 hours at the second interview had a fully adjusted hazard ratio of mortality from noncardiovascular causes of 2.06, compared with 1.44 for those who slept less.

Investigators found a positive association between marital status and sleep duration. Married women were more likely to sleep longer, while married men were more likely to average 7–8 hours of sleep per night.

The connection between sleep duration and body mass index wasn't as clear cut. At the Whitehall II study's baseline, higher BMI was associated both with short and long sleep duration in women, but only with short sleep duration in men. By 1992–1993, BMI and sleep duration showed no association in women, but both short and long sleep durations were associated with higher BMI in men.

“Patients reporting a decrease in sleep should be regarded as higher risk populations for cardiovascular and all-cause mortality,” according to the investigators. Advising patients who may sleep too long to curtail their sleep should “at least be considered,” the investigators wrote.

Both too much sleep and not enough sleep appear to be associated with increased mortality, according to a new longitudinal study.

Sleeping less than 6 hours per night or more than 9 hours per night was associated with almost twice the mortality risk of sleeping 6–8 hours per night, according to an analysis of sleep data from a prospective cohort study of more than 10,000 British civil servants.

The findings were recently presented at a meeting of the British Sleep Society, and the research article has been accepted for publication in the journal Sleep.

The investigators found that a decrease in the amount of time slept was associated with increased mortality from cardiovascular causes. An increase in sleep time was associated with an excess of mortality from all other causes, according to Jane Ferrie, Ph.D., of University College London, and her colleagues.

Previous studies have reported a U-shaped relationship between time spent sleeping and mortality, the investigators said. What has not been looked at by a sleep study before is the effect a change in sleep patterns might have.

The researchers examined sleep data collected from British civil service employees aged 35–55 years who were enrolled beginning in 1985 in a long-term study known as Whitehall II. Baseline sleep duration data were available for 9,781 subjects who were interviewed in 1985–1988, while follow-up data were available for 7,729 who were interviewed again in 1992–1993. Mortality data were available through September 2004.

After adjustment for factors such as age, sex, smoking status, body mass index, cholesterol, and physical activity, those Whitehall II participants who reported sleeping 5 hours or less a night at the first interview had a hazard ratio of death from all causes of 1.24, relative to those who slept 7 hours per night. Those who slept 9 hours or more had a fully adjusted hazard ratio of 1.54.

The fully adjusted hazard ratios of all-cause mortality were slightly higher for those who reported sleep for 5 hours or less and 9 hours or more at the second interview, 1.78 and 1.95, respectively. The risk of death due to cardiovascular causes was relatively greater for those who slept less after the baseline period than for those who slept more.

Participants whose sleep decreased from 6–8 hours a night at the first interview to less than 6 hours at the second interview had a fully adjusted hazard ratio of mortality from cardiovascular cause of 2.04, compared with 1.22 for those who slept more. Those whose sleep increased from 7–8 hours at the first interview to more than 8 hours at the second interview had a fully adjusted hazard ratio of mortality from noncardiovascular causes of 2.06, compared with 1.44 for those who slept less.

Investigators found a positive association between marital status and sleep duration. Married women were more likely to sleep longer, while married men were more likely to average 7–8 hours of sleep per night.

The connection between sleep duration and body mass index wasn't as clear cut. At the Whitehall II study's baseline, higher BMI was associated both with short and long sleep duration in women, but only with short sleep duration in men. By 1992–1993, BMI and sleep duration showed no association in women, but both short and long sleep durations were associated with higher BMI in men.

“Patients reporting a decrease in sleep should be regarded as higher risk populations for cardiovascular and all-cause mortality,” according to the investigators. Advising patients who may sleep too long to curtail their sleep should “at least be considered,” the investigators wrote.

Both too much sleep and not enough sleep appear to be associated with increased mortality, according to a new longitudinal study.

Sleeping less than 6 hours per night or more than 9 hours per night was associated with almost twice the mortality risk of sleeping 6–8 hours per night, according to an analysis of sleep data from a prospective cohort study of more than 10,000 British civil servants.

The findings were recently presented at a meeting of the British Sleep Society, and the research article has been accepted for publication in the journal Sleep.

The investigators found that a decrease in the amount of time slept was associated with increased mortality from cardiovascular causes. An increase in sleep time was associated with an excess of mortality from all other causes, according to Jane Ferrie, Ph.D., of University College London, and her colleagues.

Previous studies have reported a U-shaped relationship between time spent sleeping and mortality, the investigators said. What has not been looked at by a sleep study before is the effect a change in sleep patterns might have.

The researchers examined sleep data collected from British civil service employees aged 35–55 years who were enrolled beginning in 1985 in a long-term study known as Whitehall II. Baseline sleep duration data were available for 9,781 subjects who were interviewed in 1985–1988, while follow-up data were available for 7,729 who were interviewed again in 1992–1993. Mortality data were available through September 2004.

After adjustment for factors such as age, sex, smoking status, body mass index, cholesterol, and physical activity, those Whitehall II participants who reported sleeping 5 hours or less a night at the first interview had a hazard ratio of death from all causes of 1.24, relative to those who slept 7 hours per night. Those who slept 9 hours or more had a fully adjusted hazard ratio of 1.54.

The fully adjusted hazard ratios of all-cause mortality were slightly higher for those who reported sleep for 5 hours or less and 9 hours or more at the second interview, 1.78 and 1.95, respectively. The risk of death due to cardiovascular causes was relatively greater for those who slept less after the baseline period than for those who slept more.

Participants whose sleep decreased from 6–8 hours a night at the first interview to less than 6 hours at the second interview had a fully adjusted hazard ratio of mortality from cardiovascular cause of 2.04, compared with 1.22 for those who slept more. Those whose sleep increased from 7–8 hours at the first interview to more than 8 hours at the second interview had a fully adjusted hazard ratio of mortality from noncardiovascular causes of 2.06, compared with 1.44 for those who slept less.

Investigators found a positive association between marital status and sleep duration. Married women were more likely to sleep longer, while married men were more likely to average 7–8 hours of sleep per night.

The connection between sleep duration and body mass index wasn't as clear cut. At the Whitehall II study's baseline, higher BMI was associated both with short and long sleep duration in women, but only with short sleep duration in men. By 1992–1993, BMI and sleep duration showed no association in women, but both short and long sleep durations were associated with higher BMI in men.

“Patients reporting a decrease in sleep should be regarded as higher risk populations for cardiovascular and all-cause mortality,” according to the investigators. Advising patients who may sleep too long to curtail their sleep should “at least be considered,” the investigators wrote.