# Television and computer use and dementia risk in older adults with limited leisure or social activities: A prospective cohort study

## TL;DR

Moderate computer use may lower dementia risk in older adults with limited social activities, but excessive use and heavy TV watching are linked to higher risk.

## Contribution

This study identifies optimal limits for computer use and highlights subgroup-specific risks for dementia in socially inactive older adults.

## Key findings

- Computer use up to 2.4 hours/day was linked to lower dementia risk, but higher use increased risk.
- Television viewing above 2.1 hours/day was associated with increased dementia risk, particularly for vascular dementia.
- Heavy computer use was more harmful for APOE-ε4 homozygotes and younger adults (<65 years).

## Abstract

Associations between television/computer use and dementia in socially inactive older adults remain unclear, and optimal limits are unknown.

We followed 89,671 dementia‐free, socially inactive adults aged ≥55 from UK Biobank for a mean of 12.2 years. Adjusted Cox models assessed associations with incident all‐cause dementia and subtypes.

Computer use ≤2.4 h/day was associated with lower all‐cause dementia risk (hazard ratio [HR] 0.88; 95% confidence interval [CI] 0.82–0.94), whereas higher use increased risk (HR 1.19, 95% CI 1.05–1.34); patterns were similar for Alzheimer's and vascular dementia. Television viewing showed no association below 2.06 h/day but higher risk thereafter (HR 1.17; 95% CI 1.03–1.32), with a roughly linear increase for vascular dementia. Heavy computer use in apolipoprotein E (APOE) ‐ε4 homozygotes and higher television viewing in adults < 65 were more harmful.

In socially inactive older adults, moderate computer use may be protective, whereas higher computer use and television viewing are linked to increased dementia risk.

Among socially inactive older adults, computer use showed a J‐shaped association with all‐cause dementia: up to about 2.4 h/day was associated with lower risk, whereas higher use was associated with increased risk.The J‐shaped pattern extended to Alzheimer's disease with an inflection near 2.4 h/day and to vascular dementia with an inflection near 2.2 h/day, while no association was observed for frontotemporal dementia.Television viewing below about 2.1 h/day was not associated with higher all‐cause dementia risk, but risk increased at higher viewing times.Television viewing showed a roughly linear increase in vascular dementia risk and an apparent reduction in Alzheimer's disease risk that is likely spurious and should be interpreted with caution.Risk varied by subgroup: heavy computer use was particularly harmful among apolipoprotein E (APOE) ‐ε4 homozygotes, and higher television time was more detrimental in adults younger than 65 years.

Among socially inactive older adults, computer use showed a J‐shaped association with all‐cause dementia: up to about 2.4 h/day was associated with lower risk, whereas higher use was associated with increased risk.

The J‐shaped pattern extended to Alzheimer's disease with an inflection near 2.4 h/day and to vascular dementia with an inflection near 2.2 h/day, while no association was observed for frontotemporal dementia.

Television viewing below about 2.1 h/day was not associated with higher all‐cause dementia risk, but risk increased at higher viewing times.

Television viewing showed a roughly linear increase in vascular dementia risk and an apparent reduction in Alzheimer's disease risk that is likely spurious and should be interpreted with caution.

Risk varied by subgroup: heavy computer use was particularly harmful among apolipoprotein E (APOE) ‐ε4 homozygotes, and higher television time was more detrimental in adults younger than 65 years.