This study aimed to investigate the association between shift work and incident dementia in two population-based cohorts from the Swedish Twin Registry (STR). The STR-1973 sample included 13,283 participants born 1926-1943 who received a mailed questionnaire in 1973 that asked about status (ever/never) and duration (years) of shift work employment. The Screening Across the Lifespan Twin (SALT) sample included 41,199 participants born 1900-1958 who participated in a telephone interview in 1998-2002 that asked about night work status and duration. Dementia diagnoses came from Swedish patient registers. Cox proportional-hazards regression was used to estimate hazard ratios (HR) with 95% confidence intervals (CI). Potential confounders such as age, sex, education, diabetes, cardiovascular disease and stroke were included in adjusted models. In genotyped subsamples (n = 2977 in STR-1973; n = 10,366 in SALT), APOE e4 status was considered in models. A total of 983 (7.4%) and 1979 (4.8%) dementia cases were identified after a median of 41.2 and 14.1 years follow-up in the STR-1973 and SALT sample, respectively. Ever shift work (HR 1.36, 95% CI 1.15-1.60) and night work (HR 1.12, 95% CI 1.01-1.23) were associated with higher dementia incidence. Modest dose-response associations were observed, where longer duration shift work and night work predicted increased dementia risk. Among APOE e4 carriers, individuals exposed to =?20 years of shift work and night work had increased dementia risk compared to day workers. Findings indicate that shift work, including night shift work, compared to non-shift jobs is associated with increased dementia incidence. Confirmation of findings is needed.
Cites: Scand J Work Environ Health. 2017 Sep 1;43(5):485-493 PMID 28362457
Cites: Ugeskr Laeger. 2008 Aug 11;170(33):2423-7 PMID 18761821
Cites: Am J Geriatr Psychiatry. 2014 Nov;22(11):1262-71 PMID 23954041
Cites: Scand J Work Environ Health. 2017 Mar 1;43(2):117-126 PMID 28245504
Cites: Int Psychogeriatr. 2002 Sep;14(3):273-89 PMID 12475088
This study investigated the associations between night work, sleep and disability pension (DP) due to musculoskeletal disorders (MSD), while controlling for several confounding factors including both genetic factors and shared family background.
The study sample consisted of 27 165 Swedish twin individuals born in 1935-58 with comprehensive survey data on sociodemographic, health and lifestyle factors. Night work was assessed as years of working hours at night at least every now and then, and categorized into 'not at all, 1-10 years and over 10 years'. Data on DP with MSD (ICD-diagnoses M00-M99) were obtained from the National Social Insurance Agency. Follow-up was from the time of the interview in 1998-2003 until 2013. Information on the length and quality of sleep was available for a sub-sample of twins (n = 1684). Cox proportional hazards models were used to calculate hazard ratios (HR) with 95% confidence intervals (CI).
During the follow-up, 1338 (5%) participants were granted DP due to MSD. Both 1-10 years (HR 1.33, 95% CI 1.17-1.53) and over 10 years of night work (HR 1.39 95% CI 1.18-1.64) increased the risk of future DP. The associations were not affected by health, lifestyle or sleep factors. In the discordant twin pair analysis, the associations between night work and DP due to MSD attenuated.
Night work was associated with increased risk of DP due to MSD independently from health and lifestyle factors. Familial confounding could not be ruled out.