Life-long risk reduction could cut late dementia by a third

(Second of two parts)

Tackling poor childhood education is a daunting task and requires commitment from both public and private sectors, the report noted, but its importance cannot be overstated.

• Hearing loss at midlife – This emerged as the most powerful risk factor in the analysis, conferring an independent nine percent increased risk of dementia, a relatively new idea that has not been included in previous calculations of population attributable factors according to the commission. The mechanism of increased risk isn’t clear, but maybe a combination of neurodegeneration and social isolation imposed by being shut out of easy communication. It’s unclear whether hearing aids can mitigate the effects of hearing loss on dementia risk, the report noted.

• Hypertension, obesity and diabetes – Respectively, these accounted for two percent, one percent and one percent of the PAF. Obesity is linked to prediabetes and diabetes, which are in turn linked to insulin resistance, decreasing brain amyloid clearance, high blood glucose, and inflammation – all risks for Alzheimer’s disease.

The report recommends that one aged 45-65 years who had hypertension should be actively treated for the disorder.

• Smoking – At five percent, smoking posted the 3rd-highest PAF. The risk is probably mediated through smoking’s detrimental effects on cardiovascular health. But the report noted that tobacco smoke contains known neurotoxins as well.

Preventing the smoking/dementia connection is simple. Simply stop smoking. If you are smoking, just stop. Please.

• Depression – Depression in late life imposed a four percent PAF. The evidence reviewed suggested that depression is not, in fact, linked to dementia when experienced at midlife. But late-life depression may be prodromal symptom of dementia and biologically linked to increased stress hormones, decreased hippocampal volume. The commission noted animal models that suggest some antidepressants, including citalopram, decrease amyloid progression.

• Social isolation – Associated with a two percent PAF, social isolation may, like depression, be a prodromal symptom. But, the report said, there is growing evidence that it actually is an independent risk factor as well. It has been shown to also increase the risk of hypertension, cardiovascular disease, and depression, all dementia risk factors in their own right.

Longitudinal studies suggest that social activities and personal connections may prevent or delay dementia, although top-grade evidence is lacking. Still maintaining a rich social network not only reduces the chance of isolation, but helps prevent depression as well.

• Physical Inactivity – Sedentary life-style carried a three percent PAF for dementia. Older adults who maintain physical activity are more likely to remain cognitively intact. Physical exercise improves mood, reduces the risk of falls, and maintains normal physical function. The report cited a meta-analysis of 16 studies and almost 164,000 participants without dementia; it concluded that those in the highest level of activity had a 25 percent decreased risk of all-cause dementia and a 45 percent decreased risk of Alzheimer’s disease.

The strongest evidence for exercise’s benefit on cognition maybe from the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability(FINGER). Patients with a high risk of dementia who completed the lifestyle modification program of healthy diet cognitive training, vascular risk factor management, and aerobic exercise showed a slowing of cognitive decline and improvements in executive function and processing speed.

Becoming aware of the risk factors is one thing, the report said. Doing something about them is another. In general, the first step is to be ambitious about prevention.

Prevention is always better than treatment. We need to start thinking about dementia not as something that simply happens outside our control, but as something we can have an effect on.

The Lancet commissioned the report.