What is the clinical evidence from this study?

Study design: Cohort. Population: Cognitive impairment (n=6116). Intervention: Heavy multimorbidity burden (≥ 3 conditions) vs. No chronic diseases. Primary outcome: Incident cognitive impairment (MMSE score < 24) (RR 1.39, 95% CI 1.22-1.59, p=<0.001).

What does this research mean for the field?

Heavy multimorbidity burden (≥ 3 conditions) increases the risk of cognitive impairment by 39%, whereas a healthy lifestyle reduces the risk by approximately 40% regardless of multimorbidity burden. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

January 2, 2024Open Access

Multimorbidity, healthy lifestyle, and the risk of cognitive impairment in Chinese older adults: a longitudinal cohort study

Q: What are the key findings of this study?

Heavy multimorbidity burden (≥ 3 conditions) increased the risk of cognitive impairment by 39% (RR 1.39), whereas a healthy lifestyle reduced the risk by approximately 40%.

Q: What does this research mean for the field?

Heavy multimorbidity burden (≥ 3 conditions) increases the risk of cognitive impairment by 39%, whereas a healthy lifestyle reduces the risk by approximately 40% regardless of multimorbidity burden. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Key Result

Heavy multimorbidity burden (≥ 3 conditions) increased the risk of cognitive impairment by 39% (RR 1.39), whereas a healthy lifestyle reduced the risk by approximately 40%.

Study Design

Type

Cohort (n=6,116)

Multicenter

Yes

Structured PICO

Does a healthy lifestyle reduce the risk of cognitive impairment in older adults regardless of multimorbidity burden?

Population

6,116 Chinese adults aged ≥ 65 years (mean age 79.13, 53.07% male) from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). Key exclusions: missing MMSE score, MMSE score < 24 at baseline, self-reported diagnosis of dementia, or age < 65 at enrollment.

Intervention

Healthy lifestyle (score 8-10 based on smoking, alcohol, BMI, outdoor activities, and diet) and multimorbidity burden (≥3 coexisting chronic diseases).

Comparator

Unhealthy lifestyle (score 0-6) and no chronic diseases.

Outcome

Incident cognitive impairment, defined as a Mini-Mental State Examination (MMSE) score < 24, during a median follow-up of 5.8 years.

A healthy lifestyle is associated with a significantly reduced risk of cognitive impairment in older adults, even among those with a high burden of multimorbidity.

Main Result

Effect estimate: RR 1.39 (95% CI 1.22-1.59)

p-value: p=<0.001

Limitations

Reliance on self-reported diagnosis of chronic diseases may introduce recall bias and misclassification
The healthy lifestyle score used has not been validated yet
Use of MMSE score < 24 instead of comprehensive clinical evaluations could cause misclassification or false positive diagnosis
Potential selection bias due to missing MMSE scores, loss to follow-up, and death prior to follow-up
Observational nature of the study means findings do not necessarily imply causality

Abstract

BACKGROUND: Evidence on the association between multimorbidity and cognitive impairment in Chinese older population is limited. In addition, whether a healthy lifestyle can protect cognitive function in multimorbid older population remains unknown. METHODS: A total of 6116 participants aged ≥ 65 years from the Chinese Longitudinal Healthy Longevity Survey were followed up repeatedly. The number of coexisting chronic diseases was used for assessing multimorbidity and cardiometabolic multimorbidity. Three lifestyle statuses (unhealthy, intermediate, and healthy) were defined based on a lifestyle score covering smoking, alcohol drinking, body mass index, outdoor activities, and dietary pattern. Cognitive impairment was defined as the Mini-Mental State Examination score < 24. A modified Poisson regression model with robust error variance was used to assess the associations between multimorbidity, healthy lifestyle, and cognitive impairment. RESULTS: During a median follow-up period of 5.8 years, 1621 incident cases of cognitive impairment were identified. The relative risk (RR) of cognitive impairment associated with heavy multimorbidity burden (≥ 3 conditions) was 1.39 (95% confidence interval: 1.22-1.59). This association declined with age, with RRs being 3.08 (1.78-5.31), 1.40 (1.04-1.87), and 1.19 (1.01-1.40) in subjects aged < 70 years, ≥ 70 and < 80 years, and ≥ 80 years, respectively (P for interaction = 0.001). Compared to unhealthy lifestyle, a healthy lifestyle was related to an approximately 40% reduced risk of cognitive impairment regardless of multimorbidity burden. Among the 5 lifestyle factors assessed, daily outdoor activities and a healthy dietary pattern showed convincing protective effects on cognitive function. CONCLUSIONS: The relationship between multimorbidity and cognitive impairment is age-dependent but remains significant in the population aged 80 years or older. A healthy lifestyle may protect cognitive function regardless of the multimorbidity burden. These findings highlight the importance of targeting individuals with heavy multimorbidity burden and promoting a heathy lifestyle to prevent cognitive impairment in Chinese older population.

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