Insomnia and the Risk of Incident Heart Failure
Insomnia and the Risk of Incident Heart Failure
The prevalence of having difficulties initiating sleep almost every night, having difficulties maintaining sleep almost every night, and having non-restorative sleep more than once a week were 3.4%, 2.5%, and 8.1%, respectively.
Table 1 displays the characteristics of the study population according to the cumulative number of insomnia symptoms. The individual insomnia symptoms, i.e. difficulty initiating sleep, difficulty maintaining sleep, and that of non-restorative sleep, showed largely similar associations with these characteristics (data not shown). Older participants were more likely to have insomnia symptoms and symptoms were more frequent in women than men. In general, insomnia symptoms were associated with cardiovascular risk factors in a dose-dependent manner. There was also a strong association between insomnia symptoms and depression, anxiety, and the use of sleep medication/sedatives.
Characteristics of the study population at baseline, by the HF status at follow-up, are shown in Table 2 . Heart failure was more frequent among older participants and in men, and at baseline, participants who developed HF during the follow-up were physically less active, consumed less alcohol, and were less educated than other participants. They also had more often diabetes, an unfavourable lipid profile, high blood pressure, and higher BMI.
Among the 54 279 participants, a total of 1412 were diagnosed with HF during a mean follow-up of 11.3 years (SD = 2.9 years). A total of 1004 cases were diagnosed at hospital admission, and 408 cases were identified based on information from the National Cause of Death Register.
Table 3 presents the age- and sex-adjusted HRs and several multi-variable adjusted HRs for incident HF in relation to the individual insomnia symptoms. Having difficulty initiating sleep almost every night, difficulty maintaining sleep almost every night, and having the feeling of non-restorative sleep more than once a week were associated with an increased risk of incident HF compared with those who reported never or almost never to have these symptoms. After adjustment for established cardiovascular risk factors and previous AMI, the strength of the associations was attenuated. The estimates of effect were further attenuated after adjustment for depression and anxiety.
The HRs for HF when insomnia with influence on work was compared with insomnia that did not have such an influence were 1.53 (95% CI: 1.10–2.12) and 1.31 (95% CI: 0.86–1.98) in Models 1 and 3, respectively. The associations were not substantially different in the other models.
The cumulative number of insomnia symptoms was associated with an increased risk of HF in a dose-dependent manner in all models ( Table 4 ). The age- and sex-adjusted HRs (with 95% CI) between insomnia and overall mortality were 1.24 (1.08–1.43), 1.65 (1.37–2.00), and 2.39 (1.75–3.26) for one, two, and three insomnia symptoms, respectively, compared with participants who reported no symptoms. The corresponding multi-adjusted estimates (according to Model 3 in Table 4 ) were 1.20 (1.02–1.41), 1.38 (1.10–1.73), and 2.03 (1.39–2.95).
Figures 2 and 3 show Kaplan–Meier curves for incident HF and overall mortality according to number of insomnia symptoms. The figures show that the number of insomnia symptoms was positively associated with both risk of HF and overall mortality.
(Enlarge Image)
Figure 2.
The Kaplan–Meier curve of incident heart failure during the follow-up according to number of insomnia symptoms.
(Enlarge Image)
Figure 3.
The Kaplan–Meier curve of overall mortality during the follow-up according to number of insomnia symptoms.
Compared with men ( Table 5 ), women appeared to have a higher relative risk of HF associated with non-restorative sleep and with the cumulative symptoms of insomnia. For other stratified variables, we found no statistical evidence for any effect modification, including age, BMI, cholesterol, education, shift work, blood pressure, and smoking status.
A total of 1073 HF cases occurred after the fifth year of follow-up, and even after the exclusion of the first 5 years the estimated associations remained unchanged. For example, in Model 3, the HR for having three insomnia symptoms was 4.57 (95% CI: 1.85–11.25).
We obtained similar results by restricting follow-up to hospital confirmed cases of HF (n = 1004, data not shown).
Adjustment for chronic diseases (n = 33 819) only slightly attenuated the association of insomnia with HF risk compared with the results of the main analyses. For example, in Model 3, the HR for having three insomnia symptoms was 4.21 (95% CI: 1.84–9.61).
The association between insomnia and HF risk did not substantially change after adjustment for the use of sleep medications/sedatives. For example, in Model 3, the HR for having three insomnia symptoms was 4.33 (1.80–10.41).
Adjustment for time since last meal did not influence the estimates (data not shown).
In the present study, a total of 1715 participants had a previous AMI at baseline and 2928 had an AMI during the follow-up. Among HF patients, 299 participants had a previous AMI at baseline and 431 had an AMI during the follow-up. No appreciable change in our estimates occurred after adjustment for incident AMI as a time-dependent covariate during the follow-up (data not shown).
Results
The prevalence of having difficulties initiating sleep almost every night, having difficulties maintaining sleep almost every night, and having non-restorative sleep more than once a week were 3.4%, 2.5%, and 8.1%, respectively.
Table 1 displays the characteristics of the study population according to the cumulative number of insomnia symptoms. The individual insomnia symptoms, i.e. difficulty initiating sleep, difficulty maintaining sleep, and that of non-restorative sleep, showed largely similar associations with these characteristics (data not shown). Older participants were more likely to have insomnia symptoms and symptoms were more frequent in women than men. In general, insomnia symptoms were associated with cardiovascular risk factors in a dose-dependent manner. There was also a strong association between insomnia symptoms and depression, anxiety, and the use of sleep medication/sedatives.
Characteristics of the study population at baseline, by the HF status at follow-up, are shown in Table 2 . Heart failure was more frequent among older participants and in men, and at baseline, participants who developed HF during the follow-up were physically less active, consumed less alcohol, and were less educated than other participants. They also had more often diabetes, an unfavourable lipid profile, high blood pressure, and higher BMI.
Among the 54 279 participants, a total of 1412 were diagnosed with HF during a mean follow-up of 11.3 years (SD = 2.9 years). A total of 1004 cases were diagnosed at hospital admission, and 408 cases were identified based on information from the National Cause of Death Register.
Table 3 presents the age- and sex-adjusted HRs and several multi-variable adjusted HRs for incident HF in relation to the individual insomnia symptoms. Having difficulty initiating sleep almost every night, difficulty maintaining sleep almost every night, and having the feeling of non-restorative sleep more than once a week were associated with an increased risk of incident HF compared with those who reported never or almost never to have these symptoms. After adjustment for established cardiovascular risk factors and previous AMI, the strength of the associations was attenuated. The estimates of effect were further attenuated after adjustment for depression and anxiety.
The HRs for HF when insomnia with influence on work was compared with insomnia that did not have such an influence were 1.53 (95% CI: 1.10–2.12) and 1.31 (95% CI: 0.86–1.98) in Models 1 and 3, respectively. The associations were not substantially different in the other models.
The cumulative number of insomnia symptoms was associated with an increased risk of HF in a dose-dependent manner in all models ( Table 4 ). The age- and sex-adjusted HRs (with 95% CI) between insomnia and overall mortality were 1.24 (1.08–1.43), 1.65 (1.37–2.00), and 2.39 (1.75–3.26) for one, two, and three insomnia symptoms, respectively, compared with participants who reported no symptoms. The corresponding multi-adjusted estimates (according to Model 3 in Table 4 ) were 1.20 (1.02–1.41), 1.38 (1.10–1.73), and 2.03 (1.39–2.95).
Figures 2 and 3 show Kaplan–Meier curves for incident HF and overall mortality according to number of insomnia symptoms. The figures show that the number of insomnia symptoms was positively associated with both risk of HF and overall mortality.
(Enlarge Image)
Figure 2.
The Kaplan–Meier curve of incident heart failure during the follow-up according to number of insomnia symptoms.
(Enlarge Image)
Figure 3.
The Kaplan–Meier curve of overall mortality during the follow-up according to number of insomnia symptoms.
Compared with men ( Table 5 ), women appeared to have a higher relative risk of HF associated with non-restorative sleep and with the cumulative symptoms of insomnia. For other stratified variables, we found no statistical evidence for any effect modification, including age, BMI, cholesterol, education, shift work, blood pressure, and smoking status.
Sensitivity Analyses
A total of 1073 HF cases occurred after the fifth year of follow-up, and even after the exclusion of the first 5 years the estimated associations remained unchanged. For example, in Model 3, the HR for having three insomnia symptoms was 4.57 (95% CI: 1.85–11.25).
We obtained similar results by restricting follow-up to hospital confirmed cases of HF (n = 1004, data not shown).
Adjustment for chronic diseases (n = 33 819) only slightly attenuated the association of insomnia with HF risk compared with the results of the main analyses. For example, in Model 3, the HR for having three insomnia symptoms was 4.21 (95% CI: 1.84–9.61).
The association between insomnia and HF risk did not substantially change after adjustment for the use of sleep medications/sedatives. For example, in Model 3, the HR for having three insomnia symptoms was 4.33 (1.80–10.41).
Adjustment for time since last meal did not influence the estimates (data not shown).
In the present study, a total of 1715 participants had a previous AMI at baseline and 2928 had an AMI during the follow-up. Among HF patients, 299 participants had a previous AMI at baseline and 431 had an AMI during the follow-up. No appreciable change in our estimates occurred after adjustment for incident AMI as a time-dependent covariate during the follow-up (data not shown).
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