Night shift work, long working hours and dementia:: a longitudinal study of the Danish Work Environment Cohort

Kirsten Nabe-Nielsen; Åse Marie Hansen; Kazi  Ishtiak-Ahmed; Matias  Brodsgaard Grynderup; Finn Gyntelberg; Sabrina Islamoska; Erik Lykke Mortensen; T.K.T. Phung; Naja Hulvej Rod; Gunhild Waldemar; Rudi GJ Westendorp; Anne Helene Garde

doi:10.1136/bmjopen-2018-027027

Night shift work, long working hours and dementia: a longitudinal study of the Danish Work Environment Cohort

Kirsten Nabe-Nielsen, Åse Marie Hansen, Kazi Ishtiak-Ahmed, Matias Brodsgaard Grynderup, Finn Gyntelberg, Sabrina Islamoska, Erik Lykke Mortensen, T.K.T. Phung, Naja Hulvej Rod, Gunhild Waldemar, Rudi GJ Westendorp, Anne Helene Garde

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Abstract

Objective Shift work and long working hours are potential risk factors for dementia, but previous studies on shift work, long working hours and dementia are sparse and their findings are conflicting. Therefore, we investigated the effect of night shift work and long working hours on dementia. Design A longitudinal study. Setting Denmark. Participants 3435 occupationally active men and women from the general working population. Methods Work schedule covered day work (reference) and shift schedules without/with night work. Working hours covered <27, 28-36, 37 (reference), 38-44, and ≥45 hours/week. As the primary outcome, we used register-based information about dementia, and estimated incidence rate ratios (IRR) and 95% CI. Estimates were adjusted for gender, age, psychosocial work factors and cardiovascular risk factors. Results We identified 85 dementia cases during a mean of 9.8 years of follow-up. We found a positive, but statistically insignificant association between night shift work and dementia (IRR=2.01; 95% CI: 0.87-4.65). Post hoc analyses indicated that this was only due to a higher risk in permanent night workers (IRR=3.25; 95% CI: 1.35-7.83). The dementia risk was also significantly higher among participants working 38-44 hours/week (IRR=2.08; 95% CI: 1.11-3.90) compared with those working 37 hours/week. We found no indications of a higher risk of dementia in participants working <37 hours/week or ≥45 hours/week. Conclusion We did not find arguments that night shift work or long working hours increased dementia risk in general. However, we found a higher risk of dementia in specific subgroups, that is, permanent night workers and employees with moderately longer weekly working hours than the standard.

Original language	Danish
Journal	BMJ Open
ISSN	2044-6055
DOIs	https://doi.org/10.1136/bmjopen-2018-027027
Publication status	Published - 1 May 2019

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Cite this

Nabe-Nielsen, K., Hansen, Å. M., Ishtiak-Ahmed, K., Brodsgaard Grynderup, M., Gyntelberg, F., Islamoska, S., Mortensen, E. L., Phung, T. K. T., Rod, N. H., Waldemar, G., Westendorp, R. GJ., & Garde, A. H. (2019). Night shift work, long working hours and dementia: a longitudinal study of the Danish Work Environment Cohort. BMJ Open. https://doi.org/10.1136/bmjopen-2018-027027

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title = "Night shift work, long working hours and dementia:: a longitudinal study of the Danish Work Environment Cohort",

abstract = "Objective Shift work and long working hours are potential risk factors for dementia, but previous studies on shift work, long working hours and dementia are sparse and their findings are conflicting. Therefore, we investigated the effect of night shift work and long working hours on dementia. Design A longitudinal study. Setting Denmark. Participants 3435 occupationally active men and women from the general working population. Methods Work schedule covered day work (reference) and shift schedules without/with night work. Working hours covered <27, 28-36, 37 (reference), 38-44, and ≥45 hours/week. As the primary outcome, we used register-based information about dementia, and estimated incidence rate ratios (IRR) and 95% CI. Estimates were adjusted for gender, age, psychosocial work factors and cardiovascular risk factors. Results We identified 85 dementia cases during a mean of 9.8 years of follow-up. We found a positive, but statistically insignificant association between night shift work and dementia (IRR=2.01; 95% CI: 0.87-4.65). Post hoc analyses indicated that this was only due to a higher risk in permanent night workers (IRR=3.25; 95% CI: 1.35-7.83). The dementia risk was also significantly higher among participants working 38-44 hours/week (IRR=2.08; 95% CI: 1.11-3.90) compared with those working 37 hours/week. We found no indications of a higher risk of dementia in participants working <37 hours/week or ≥45 hours/week. Conclusion We did not find arguments that night shift work or long working hours increased dementia risk in general. However, we found a higher risk of dementia in specific subgroups, that is, permanent night workers and employees with moderately longer weekly working hours than the standard.",

author = "Kirsten Nabe-Nielsen and Hansen, {{\AA}se Marie} and Kazi Ishtiak-Ahmed and {Brodsgaard Grynderup}, Matias and Finn Gyntelberg and Sabrina Islamoska and Mortensen, {Erik Lykke} and T.K.T. Phung and Rod, {Naja Hulvej} and Gunhild Waldemar and Westendorp, {Rudi GJ} and Garde, {Anne Helene}",

year = "2019",

month = may,

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doi = "10.1136/bmjopen-2018-027027",

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TY - JOUR

T1 - Night shift work, long working hours and dementia:

T2 - a longitudinal study of the Danish Work Environment Cohort

AU - Nabe-Nielsen, Kirsten

AU - Hansen, Åse Marie

AU - Ishtiak-Ahmed, Kazi

AU - Brodsgaard Grynderup, Matias

AU - Gyntelberg, Finn

AU - Islamoska, Sabrina

AU - Mortensen, Erik Lykke

AU - Phung, T.K.T.

AU - Rod, Naja Hulvej

AU - Waldemar, Gunhild

AU - Westendorp, Rudi GJ

AU - Garde, Anne Helene

PY - 2019/5/1

Y1 - 2019/5/1

N2 - Objective Shift work and long working hours are potential risk factors for dementia, but previous studies on shift work, long working hours and dementia are sparse and their findings are conflicting. Therefore, we investigated the effect of night shift work and long working hours on dementia. Design A longitudinal study. Setting Denmark. Participants 3435 occupationally active men and women from the general working population. Methods Work schedule covered day work (reference) and shift schedules without/with night work. Working hours covered <27, 28-36, 37 (reference), 38-44, and ≥45 hours/week. As the primary outcome, we used register-based information about dementia, and estimated incidence rate ratios (IRR) and 95% CI. Estimates were adjusted for gender, age, psychosocial work factors and cardiovascular risk factors. Results We identified 85 dementia cases during a mean of 9.8 years of follow-up. We found a positive, but statistically insignificant association between night shift work and dementia (IRR=2.01; 95% CI: 0.87-4.65). Post hoc analyses indicated that this was only due to a higher risk in permanent night workers (IRR=3.25; 95% CI: 1.35-7.83). The dementia risk was also significantly higher among participants working 38-44 hours/week (IRR=2.08; 95% CI: 1.11-3.90) compared with those working 37 hours/week. We found no indications of a higher risk of dementia in participants working <37 hours/week or ≥45 hours/week. Conclusion We did not find arguments that night shift work or long working hours increased dementia risk in general. However, we found a higher risk of dementia in specific subgroups, that is, permanent night workers and employees with moderately longer weekly working hours than the standard.

AB - Objective Shift work and long working hours are potential risk factors for dementia, but previous studies on shift work, long working hours and dementia are sparse and their findings are conflicting. Therefore, we investigated the effect of night shift work and long working hours on dementia. Design A longitudinal study. Setting Denmark. Participants 3435 occupationally active men and women from the general working population. Methods Work schedule covered day work (reference) and shift schedules without/with night work. Working hours covered <27, 28-36, 37 (reference), 38-44, and ≥45 hours/week. As the primary outcome, we used register-based information about dementia, and estimated incidence rate ratios (IRR) and 95% CI. Estimates were adjusted for gender, age, psychosocial work factors and cardiovascular risk factors. Results We identified 85 dementia cases during a mean of 9.8 years of follow-up. We found a positive, but statistically insignificant association between night shift work and dementia (IRR=2.01; 95% CI: 0.87-4.65). Post hoc analyses indicated that this was only due to a higher risk in permanent night workers (IRR=3.25; 95% CI: 1.35-7.83). The dementia risk was also significantly higher among participants working 38-44 hours/week (IRR=2.08; 95% CI: 1.11-3.90) compared with those working 37 hours/week. We found no indications of a higher risk of dementia in participants working <37 hours/week or ≥45 hours/week. Conclusion We did not find arguments that night shift work or long working hours increased dementia risk in general. However, we found a higher risk of dementia in specific subgroups, that is, permanent night workers and employees with moderately longer weekly working hours than the standard.

U2 - 10.1136/bmjopen-2018-027027

DO - 10.1136/bmjopen-2018-027027

M3 - Tidsskriftartikel

C2 - 31129586

SN - 2044-6055

JO - BMJ Open

JF - BMJ Open

ER -