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Category Health & Nutrition

Age at Diagnosis 40–110 years

Biological Sex

Clinical Stage at Diagnosis

Years Since Diagnosis 0–30 years

Comorbidities (check all that apply)

Diabetes Mellitus Cardiovascular Disease Chronic Kidney Disease COPD / Respiratory Disease Cancer (Active)

Physical Activity

Social Engagement

BMI Category

Care Setting

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About

Alzheimer's disease accounts for 60 - 80% of all dementia cases. Median survival after diagnosis ranges from 3 to 11 years depending on age at diagnosis, clinical stage, and comorbidity burden. Misunderstanding prognosis leads to inadequate care planning, delayed legal arrangements, and financial exposure. This calculator applies multiplicative adjustment factors to stage-specific median survival estimates derived from population-level cohort studies (Brookmeyer et al., 2002; Todd et al., 2013). It is not a clinical instrument. It approximates population-level medians assuming typical disease progression. Individual trajectories vary. Atypical presentations, genetic factors such as APOE ε4 status, and treatment response are not modeled.

Formulas

The estimated median survival S in years is computed as a base median S_base determined by age at diagnosis, multiplied by adjustment factors for clinical stage, sex, comorbidity burden, and lifestyle modifiers:

S = S_base × f_stage × f_sex × f_activity × f_social × f_bmi × f_care × n∏i=1 c_i

where S_base = age-bracket median survival (3.5 - 10 yr), f_stage = clinical stage multiplier (0.35 - 1.3), f_sex = sex-based factor (0.90 or 1.10), f_activity = physical activity modifier, f_social = social engagement modifier, f_bmi = body mass index category modifier, f_care = care setting modifier, and c_i = comorbidity multiplier for each of n selected conditions. The optimistic bound is S × 1.35 and the conservative bound is S × 0.65, reflecting population-level variance observed in longitudinal studies.

Reference Data

Factor	Category	Median Survival Impact	Source / Notes
Age at Diagnosis	< 65 yr	8 - 12 yr median	Early-onset; slower progression typical
Age at Diagnosis	65 - 74 yr	6 - 8 yr median	Most common onset bracket
Age at Diagnosis	75 - 84 yr	4 - 6 yr median	Competing mortality increases
Age at Diagnosis	≥ 85 yr	3 - 4 yr median	Highest competing mortality
Clinical Stage	MCI / Very Early	×1.3 multiplier	Mild Cognitive Impairment; not all convert
Clinical Stage	Mild (Early)	×1.0 (baseline)	CDR 1; independent ADLs
Clinical Stage	Moderate	×0.65 multiplier	CDR 2; needs supervision
Clinical Stage	Severe (Late)	×0.35 multiplier	CDR 3; fully dependent
Comorbidity	Diabetes Mellitus	×0.85	Vascular burden accelerates decline
Comorbidity	Cardiovascular Disease	×0.80	CHF, CAD, stroke history
Comorbidity	Chronic Kidney Disease	×0.85	Stage 3+ CKD
Comorbidity	COPD / Respiratory	×0.82	Pneumonia risk in late stages
Comorbidity	Cancer (Active)	×0.70	Competing cause of death
Comorbidity	No Significant Comorbidities	×1.0	Baseline
Sex	Female	×1.10	Longer survival post-diagnosis observed
Sex	Male	×0.90	Higher mortality rate post-diagnosis
Physical Activity	Regular (≥150 min/wk)	×1.10	WHO recommendation threshold
Physical Activity	Sedentary	×0.90	Accelerated functional decline
Social Engagement	High	×1.08	Cognitive reserve theory
Social Engagement	Low / Isolated	×0.92	Depression and faster decline
BMI	Underweight (<18.5)	×0.85	Malnutrition risk in late stages
BMI	Normal (18.5 - 24.9)	×1.0	Baseline
BMI	Overweight (25 - 29.9)	×1.02	Mild protective effect observed
BMI	Obese (≥30)	×0.92	Cardiovascular complication risk
Care Setting	Home with caregiver	×1.05	Familiar environment benefit
Care Setting	Residential / Nursing	×0.95	Higher infection exposure

Frequently Asked Questions

Age is the strongest predictor. Individuals diagnosed before age 65 (early-onset) have median survival of 8-12 years because competing causes of death are fewer and biological reserve is higher. Those diagnosed after 85 have median survival of 3-4 years due to frailty, comorbidity accumulation, and reduced physiological resilience. The calculator uses published age-bracket medians from population cohort studies.

Each comorbidity independently increases mortality risk by a relative proportion. A patient with both cardiovascular disease (×0.80) and diabetes (×0.85) has a combined factor of 0.80 × 0.85 = 0.68, reflecting compounding physiological burden. This multiplicative approach mirrors the Charlson Comorbidity Index methodology used in clinical prognostic models.

No. Current FDA-approved treatments (donepezil, rivastigmine, galantamine, memantine) have modest symptomatic benefit but no proven survival extension in population studies. Newer anti-amyloid therapies (lecanemab, donanemab) show plaque reduction but long-term survival data is insufficient for inclusion. The model reflects untreated natural history trajectories.

The Clinical Dementia Rating scale ranges from 0 (normal) to 3 (severe). A patient diagnosed at CDR 1 (mild) has the full median survival window. Moderate stage (CDR 2) applies a ×0.65 factor because approximately 35% of the disease course has already elapsed. Severe stage (CDR 3) applies ×0.35 reflecting that most functional decline has occurred and median remaining survival is 1-3 years.

This tool provides population-level statistical estimates, not individual clinical prognoses. Legal and insurance documents typically require a physician's formal assessment. However, the output can inform preliminary conversations with elder law attorneys, financial planners, and care coordinators regarding approximate time horizons for long-term care budgeting and advance directive deadlines.

The range reflects ±35% variance around the median estimate. In published cohort studies, interquartile survival ranges span roughly this magnitude. The optimistic bound (×1.35) represents the 75th percentile - patients with favorable genetics, strong social support, and excellent care. The conservative bound (×0.65) represents the 25th percentile - patients with rapid progression, complications like aspiration pneumonia, or falls.

Yes. Women survive approximately 10% longer post-diagnosis than men, independent of their longer baseline life expectancy. This is attributed to differences in brain structure, hormonal neuroprotection history, and higher rates of cardiovascular mortality in males. The calculator applies a ×1.10 factor for females and ×0.90 for males based on meta-analysis data from Larson et al. (2004).